Monthly Archives: May 2018

How “Marine Vomit” is Slowly Destroying this New England Fishery

Benthic Ecology blog post by Christina Jayne

It’s easy to see why this sea squirt is called “Marine Vomit” (

Ithaca, NEW YORK – What is slimy, squishy, less than an inch long, and grows by forming a carpet of individuals on the sea floor off New England? It’s an invasive sea squirt — called “Marine Vomit”, of course. And one species in particular has taken over 140 square miles of sea floor on Georges Bank, an important scallop fishery for all of New England.


What in the world is a sea squirt?

Sea squirts, also known as tunicates, are sac-like filter-feeding animals that attach themselves to the sea floor or any hard surface. Tunicates are colonial organisms, growing in clusters that can expand to form large mats, covering the bottom

Tunicates come in all colors (

A group of scientists lead by Katherine Kaplan and Patrick Sullivan at Cornell University’s Department of Natural Resources have recently published two papers which have studied the invasion and spread of “marine vomit”, also known as the carpet sea squirt (Didemnum vexillum) throughout Georges Bank, an area important for supporting the lucrative scallop fishery. What they’ve found so far may dishearten local fishermen whose livelihoods depend on the Georges Bank.

What makes it invasive?

You may have heard the term “invasive” before, but what does that mean for an ecosystem? Scientists use the word invasive to describe a species that is living in an area outside its native range, and in many cases, may be found overgrowing or out-competing the native species. Many invasive species were brought to new regions by humans, both intentionally and  unintentionally. Invasive species have been known to wreak havoc on native ecosystems, and in case of the carpet sea squirt, Kaplan’s team has discovered it has altered animal community structure and created an additional headache for humans by growing on boat hulls and aquaculture equipment.

Where did it come from?

Researchers believe the carpet sea squirt is native to Japanese waters, and most likely came to the Atlantic on boats or on the shells of oysters brought to the Gulf of Maine for aquaculture. This species has been transported to many coastlines and has become a nuisance around the world.

The invading sea squirt was first observed at Georges Bank in 2000, and now covers an estimated 140 square miles of sea floor. Georges Bank is a large elevated portion of the seafloor, spanning an area larger than the state of Massachusetts. For over 400 years, Georges Bank supported one of the most productive fisheries for Atlantic cod and halibut, but as new bottom trawling methods were employed, these fishes were quickly wiped out, along with deep water corals and sponges that created habitat structure for other species. Now, portions of Georges Bank are federally protected and closed to fishing, but fish stocks have not recovered and the only viable fishery is for the Atlantic sea scallop (Placopecten magellanicus). Kaplan, on the hunt for the invaders, wanted to analyze a region that encompassed both closed and open areas on the bank, to understand the effect of bottom fishing on the scallops and the invasive tunicates.

Her team surveyed the target area using a unique image mapping system in which a camera is towed behind a boat and all the images taken are stitched together using computer software to create a visualization of the area. Kaplan hypothesized that bottom-fishing would have a negative impact on the scallops, and that the invaders would have a negative impact on the scallops. She was right in both cases.

With the invasive tunicate covering the bottom, juvenile sea scallops can no longer attach to the sea floor, and those that find a clear patch are often quickly covered by the invader, which smother the scallops and weigh them down, preventing their escape from predators (yes, scallops can swim) and inhibit their feeding. Kaplan’s team also found that areas open to fishing had lower densities of sea scallops.

Kaplan wanted to find if the presence of the carpet sea squirt altered the community structure and abundance of other organisms on the bank. She found the invader’s presence was negatively correlated with the Atlantic scallop, barnacles, sea urchins, and a tube anemone.

However, the invader encouraged an increased abundance of crabs, burrowing worms, and sea stars. Overall, Kaplan found that the presence of the invader sea squirt reduced biodiversity, and concluded the invader may be even worse for the region than bottom fishing, as in areas where the invader coated the sea floor, no other species were found. She found this result across the study area, as fishing protection did not make a difference.

Abundance of the sea squirt (red) and sea scallop (blue), with closed fishing area in grey. (Katherine Kaplan).

Researchers and fishermen alike are concerned for the Atlantic scallop fishery. Dockside values of North Atlantic fisheries are estimated at $800 million, with much of the production coming from the Georges Bank region. Not only does the carpet sea squirt reproduce and grow rapidly, it has no predators and continues to spread in the North Atlantic. New Zealand has had limited success trying to eradicate their own invasive population, and while covering the sea floor with various tarps or other methods may inhibit the invader, it also negatively impacts the native organisms. It seems the best approach is to educate those who might accidentally transport it elsewhere, to prevent its spread to other regions. Researchers like Kaplan and Sullivan will continue to track the presence of invaders, and hopefully international effort will help prevent the spread of other invasive species around the globe.


Kaplan, K.A., D.R. Hart, K. Hopkins, S. Gallager, A. York, R. Taylor, P.J. Sullivan (2018). Invasive tunicate restructures invertebrate community on fishing grounds and a large protected area on Georges Bank. Biological Invasions 20: 87.
Kaplan, K.A., D.R. Hart, K. Hopkins, S. Gallager, A. York, R. Taylor, P.J. Sullivan (2017). Evaluating the interaction of the invasive tunicate Didemnum vexillum with the Atlantic sea scallop Placopecten magellanicus on open and closed fishing grounds of Georges Bank. ICES Journal of Marine Science 74(9).
“Atlantic:  Georges  Bank”
“Geology and the Fishery of Georges Bank” USGS Fact Sheet

“Little bit of that good old global warming”

Not for Crabs

Benthic ecology blog by:  Olivia Soares Pereira

Global warming and climate change: four words that we have been hearing a lot in the past years, and that big round question comes up: is global warming for real? Some believe it is a hoax “created by and for the Chinese to make United States manufacturing non-competitive”. Scientists say this is the warmest year since 1880. But let’s back up a little, what is really Global Warming?

It is a fact that Earth’s climate changed throughout the history, with cycles of glacial periods and warm periods depending on how much solar radiation the Earth gets. And we might think that the warming we are experiencing is just another warm period and it’s a natural process. However, scientists have been able to gather information on a global scale through satellites and other improving technologies that shows that this time the warming rate is much faster and unprecedented over decades to millennia.

And they found out that the greenhouse effect is fastening this process. Some of the energy from the sun is trapped in the atmosphere because of gases that absorbs that energy and re-emit it in all directions – the ones called greenhouse gases. Without these gases the Earth’s surface would be 30°C colder, but with more of them, it gets warmer. Carbon dioxide (CO2) has the highest contribution to the greenhouse effect, and its concentration in the atmosphere has been increasing since the pre-industrial period. All living beings release CO2 when respiring, but the primary source of that increase is fossil fuels usage by humans. Because this specific CO2 is not derived from a natural biological process we call it as anthropogenic. Higher concentrations of CO2 increase the amount of energy trapped in the atmosphere and, therefore, the temperature. This is what is called Global Warming or Climate Change.

I hope you are convinced that the climate is changing and that the increased concentration of anthropogenic greenhouse gases is the cause of it (which means… yes, WE are driving it), so I will keep going and we will dive deeper into it. The oceans are a great sink for the extra heat in the atmosphere. Because of its physical-chemical properties, ocean waters can take up 1,000 times more heat than the atmosphere. Thus, if the atmosphere is getting warmer, the oceans are also getting warmer. But it is not only about temperature, the gases on the ocean and on the atmosphere are in equilibrium, which means that if the concentration of a certain gas increases in the atmosphere, it will also increase in the ocean. Remember CO2? Absorption of increased levels of atmospheric CO2 by the ocean has and continues to change pH levels, making the oceans mores acid, a process we call ocean acidification (OA). Intergovernmental Panel on Climate Change recent scenarios predict that ocean pH will decrease by 0.3 units and temperatures will increase by 2.6-4.8°C by 2100. These have huge implications on marine life.

 But what do crustaceans have to do with this? Increases in temperature and CO2 changes the availability of specific carbonate species that incorporate many marine invertebrates’ exoskeletons. For example, the saturation state of calcium carbonate will decline, i.e., it will be more soluble, and it will be harder for animals to form their shells and skeletons. Studies have shown that OA affects negatively a broad range of marine calcifying organisms, by changing its survival rates, calcification, growth, development and abundance. Crustaceans, however, have varied responses; some show reduced growth, others show no effect, or even enhance growth under OA conditions. OA has the potential to affect both precipitation of calcium carbonate and the availability and uptake of specific ions necessary for carapace formation. But still, little is known about the functional responses of crustaceans to OA. The exoskeleton is critical for protection from predators and from the environment (e.g. desiccation), resistance to mechanical loads both from predators and preys, and support for mobility. Alterations in its properties may significantly affect the fitness of crustaceans.

Climate change and ocean acidification: a simple scheme from fossil fuels to carbonate soluability

Scientists have been trying to assess the extent to which OA and temperature affects functional properties of decapods (roughly defined as crustaceans with ten legs, as crabs, shrimps, and lobsters). A very interesting study with blue king crabs and red king crabs from Alaska hypothesized that under low pH or elevated temperature, the resistance of their carapace would be reduced due to reduced mineral content of carbonate and a protein called chitin, main constituents of crustaceans’ exoskeleton. NOAA and New Jersey researchers exposed for a full year juvenile blue king crabs to three levels of pH, an ambient level two reduced levels. Juveniles red king crabs were exposed for 6 months to an ambient pH level and a reduced level at three levels of temperature (ambient and two warmer conditions). They then measured the hardness, thickness, and chemistry of the carapace and claw of the animals. They also checked daily for mortalities and molts (when crustaceans change their exoskeleton), recording it and removing it.

For both crabs, the hardness of the carapace did not significantly change among treatment groups, but their claws showed lower hardness in lower pH. For the red king crabs, temperature also did not change total hardness, although the thickness of their carapace was negatively affected. Finally, they verified a significant effect of pH on chemistry, with more calcium (Ca) content on lower pH for blue king crabs. For red king crabs, both pH and temperature had a negative effect on magnesium (Mg) content, which contributes to the hardness, and a positive effect on Ca content in the claws. If we put all these results together we get a situation where the crabs are expending more energy to build their claws due the increased amount of Ca content (remember that OA increase calcium carbonate solubility, making it harder to precipitate it) with lower hardness, and a thicker carapace. Those alterations in mechanical and chemical properties of the claw and carapace affects crabs’ fitness.

If you know something about king crabs, you are probably thinking that this could be just a very specific response since king crabs are mainly found in Alaskan waters and this. Blue crabs, though, are distributed across the western Atlantic Ocean, and they were also the target of a study. The authors aimed to examine the effect of increased temperature and CO2 on the carapace thickness and chemistry of juvenile crabs from Chesapeake Bay. They also exposed the crabs to different treatments: temperature representing summer conditions, with a value of CO2 just below the average for the area, and predicted future conditions (warmer with higher CO2). Each treatment was replicated twice, and crabs were sampled after two molts (27-39 days).

They verified a significant effect of temperature on thickness, with thinner, lighter carapaces associated with higher temperature. Those crabs also contained lower Ca content, showing a significant effect of temperature on it. The carapaces of crabs at high CO2 were heavier and contained more Mg, with a greater effect at high temperature. The Mg:Ca ratios were higher at high CO2, which is an indicator of reduced fitness. Again, OA can decline carapace thickness and change its chemistry. Blue crabs, though, are able to cope with changes in ions fractions in seawater, as they can form their new carapace inside the old one in a controlled environment. However, some specific chemical reactions during calcification process still make it harder for crabs to calcify carbonates, meaning there is still a huge energy cost for it.

Although king crabs and blue crabs have different life histories and distributions, both studies agree that OA has effects on carapace formation, and it seems that there are species-specific responses.

Ok, but why should I care? Take a closer look at the pictures again. Do you recognize them? Let me show you a different view then…

Crab dishes from seafood restaurants in San Diego: Crab Cake with blue crab meat from Bluewater Gril (left); king crab from Crab Town (middle); king crab from Truluck’s Seafood (right).

From simple to more complex dishes, king crabs and blue crabs are part of many seafood restaurants menu, and we can easily find them on markets. In 2011, 10,520 tons of red and blue king crab were captured, and the average final product price stays around $10.00/lb. We can then calculate a price for the king crab fishery of more than $210 bi in 2011. According to Alaska Seafood Marketing Institute, in 2016, wholesale prices for red king crab were 25%-35% higher, and this increase, despite a strong U.S. dollar, indicates a strong demand. Considering this increase in demand and prices, we would expect a market value of more than $262 bi in 2016. Most of the Alaskan king crab goes to U.S. and Japanese markets, but we can find them everywhere in the globe.

However, market values are only the economic output of fisheries, and, to get a better grasp of how much money is involved in fisheries we also have to consider the costs of employees, operating and production, maintenance, and transport. For example, NOAA’s report gives us the following costs for the year of 2014: crew share of $31.81 mi, captain share of $14.41, processing labor payment of $8.99 mi, bait expenditures of $1.47 mi, fuel expenditure of $ 3.8 mi, and imports at a value of more than $180 mi.

Blue crabs are also a huge commercial fishery, that has been historically centered on the Chesapeake Bay, and is increasing in other regions. In the U.S., it is of significant culinary and economic importance, particularly in Louisiana, North Carolina, Chesapeake Bay, and New Jersey, even becoming Maryland’s largest fishery. In 2013, its national market value was of $192 mi, and in 2016, 49.6 mi pounds of blue crabs were harvested only from Chesapeake Bay.

Summarizing everything from climate change to crabs’ market… scientific studies help us understanding the whole picture of the possible impact of a changing climate on economically valuable species, which is crucial to determine the future state of the environment. Changes in thickness, hardness and element content of those crabs’ carapace can have huge impacts on their mobility, feeding mode, protection, fitness and, therefore, survival. With a lower survival rate, their stocks will experience a decrease, having a direct effect on the national and world economy. Not even to mention their biological value and the need of management, given the fishing number, that could be a whole another article. And it is not only about crabs, we still have shrimp, lobster, oyster, and clam fisheries on top of that, which will all be also affected by OA. Economic losses of an eventual disappearance of such animals is just a fraction of the real impact in the whole planet ecosystem. So next time you read something like “U.S. leadership is indispensable to countering an anti-growth energy agenda that is detrimental to U.S. economic and energy security interests” on developing clean energy, keep all that in mind.


Alaska Seafood Marketing Institute. (2016). Alaska Crab Market Summary & Outlook.
Coffey, W. D., et al. (2017). Ocean acidification leads to altered micromechanical properties of the mineralized cuticle in juvenile red and blue king crabs. Journal of Experimental Marine Biology and Ecology, 495, 1-12.
FAO report on capture production by species, fishing areas and countries or areas for king crabs and squat-lobsters from 2002 to 2011.
Garber-Tonts, B, and Lee, J. (2016). Stock assessment and fishery evaluation report for the king and tanner crab fisheries of the Gulf of Alaska and Bering Sea/Aleutian Islands area: economic status of the BSAI king and tanner crab fisheries off Alaska. Seattle, WA.
Glandon, H. L., et al. (2018). Counteractive effects of increased temperature and pCO2 on the thickness and chemistry of the carapace of juvenile blue crab, Callinectes sapidus, from the Patuxent River, Chesapeake Bay. Journal of Experimental Marine Biology and Ecology, 498, 39-45.
NOAA Fisheries Service. Red king crab (Paralithodes camtschaticus).


Home sweet plastic?

Marine plastic pollution transforms benthic ecosystems

Benthic Ecology post by Jessica Sandoval

When we think of home, perhaps the first image that comes to mind is not a recycling bin nor an old tire. However, these items can easily become home to many marine animals on the sea floor. How do our plastic goods make their way to the sea floor and what happens to the ecosystems once plastic is introduced? In the following sections, we will address these questions as to how and why plastic becomes a home.

Plastic is still a pretty new invention

It is hard to imagine a world without plastics, although it came into mass manufacture only a few decades ago in the 1950s. Since then, plastics production has skyrocketed. Ronald Geyer and his colleagues have estimated that 8.3 billion metric tons of plastic has been produced to date, 2.5 billion tons of which are currently in use, such as in construction materials like PVC piping. 600 million metric tons have been recycled and 4.9 billion metric tons have been discarded into a landfill or released into the environment. The plastics that make it into the ocean and to the sea floor are included in the 4.9 billion tons discarded. The 4.9 billion tons in the landfill and environment at the present is the same weight as 15,000 Empire State Buildings or 650 million elephants!

But our consumption of plastic goods is only increasing as we prefer more and more single use plastics over sustainable methods. If these trends that Geyer and colleagues have measured are set to continue, they project that by 2050, about 12 billion metric tons of plastic waste will be in landfills or in the natural environment. This is the equivalent weight of 36,000 Empire State Buildings or 1.6 billion elephants that would have accumulated in landfills or in the natural environment by 2050! It is clear that plastic is and will continue to be a significant pollutant in the natural environment. But what happens to the plastics as they enter the natural environment, and specifically into the oceans?

Statistics derived from University of Georgia (Geyer 2017)

Where, oh where, does the plastic go

The answer is practically everywhere. Plastics get circulated globally from ocean currents. They have been found from the surface waters to the sea floors to the poles. Plastic takes upwards of 500 years to decompose. That means, it has a long lifespan, throughout which it can spread.

Above Left: The sea surface is littered with rafts of floating plastic (Photo Dimitar Dilkoff via Getty Images). Above Right: Plastic can also sink to the ocean floor, making it a prime habitat for benthic (sea- floor) organisms (Photo: Monterey Bay Aquarium Research Institute)

Plastic can be broken down into smaller fragments from the sun’s radiation, called UV radiation, and from mechanical wave action, for example. These small plastic bits are called microplastics, and range from the size of nanometers (about the size of a virus) to 5 mm (about the size of a sesame seed). These small bits of plastic include beads from facial scrubs and microscopic fibers from our very clothing. These are easily ingested by marine organisms and by us!

So, how do plastics affect benthic ecosystems?

They change the ecosystem dynamics (such as predation and access to food)

Marine litter affects the animals that live on or in the soft sedimented (such as sandy) sea floors. In fact, large marine plastics change the community structure of the local soft sediment ecosystem. As an example, a study was conducted in Aegean Sea in which the benthic megafauna, or sea-floor dwelling animals, were surveyed by SCUBA diving scientists for a year. In this study, 16 litter items (12 plastic bottles and 4 glass jars) were placed at SCUBA depth of 20 meters. What the study found was that the total abundance and number of species were highest on the littered plots in comparison to the control in which there was no debris present. On the glass and plastic litter, the scientists noted a large abundance of sessile (non-mobile) organisms, such as sea sponges, barnacles, and tunicates (commonly called “sea squirts”). They also reported a high abundance of mobile animals, such as hermit crabs, sea snails, octopuses, and fish. The non-mobile animals settle on the surface of the litter and formed relationships amongst each other, like competing for space or food, as they filter feed the water for nutrients. Conversely, the litter provided shelter and den opportunities for the mobile creatures.

Above: This image I acquired while aboard the Exploration Vessel Nautilus in 2017. We can see that a variety of marine life has begun to call this recycling bin home. This includes non-mobile animals such as anemones and mobile animals, such as crabs.

So, if the litter provides homes for these creatures, isn’t it helpful to have more marine litter? Hard substrates, such as rocks or bottles, are not endemic (or native) to the soft sediment sea floors. The undisturbed soft sea floor has many indigenous (or native) animals, such as Polychaetes (sea worms). These soft-sediment-loving animals could be outcompeted by new, hard-substrate-loving species given an increase in litter. This would lead to the loss of native, soft sediment species and possibly their local extinction.

Plastics act as rafts for alien species

Plastics can be rafts that float on the surface of the ocean and transport alien (non-native) species from one place to another. Upon sinking to the sea floor or landing on a new coastal environment, the rafts introduce the benthic ecosystems to alien organisms. An early British Antarctic survey found that human litter doubles rafting opportunities for animals, providing an opportunity to disperse to new lands potentially invasive species. A more recent study by researchers in Oregon focused on a tsunami that occurred in 2011 after an earthquake in East Japan. This tsunami triggered a massive transoceanic rafting event, in which 289 Japanese coastal marine species traveled thousands of kilometers to the shores of North America and Hawai’i. The large rafting event was in part attributed to the nonbiodegradable objects, primarily plastics, that were predominant components of the rafted debris from Japan. New species continue to arrive on rafts to the North American shoreline after nearly 6 years at sea. This is a 4 year longer rafting event in comparison to past studies, in which biodegradable litter, such a fallen trees, were the rafting agents. Biodegradable rafts, such as downed trees, are decomposable, making them much less likely to travel across the ocean for many years to land in foreign coastal environments. These rafts result in the arrival of alien species to the North American and Hawai’ian coastline and benthic environments. The potential for plastics to be agents of colonization by invasive species is therefore concerning.

Above: Two examples of plastic rafts that crossed the oceans after the 2011 earthquake in Japan. Left) A shipping vessel heavily covered in Japanese fauna including barnacles and mussels. Found in Washington. Right) A buoy with limpets and oysters attached. Found in Oregon. Photos: Carlton et al. 2017.

Invasive species can disrupt a benthic ecosystem in many ways. They can alter the dynamics of a sea- floor community by competing for space or food resources with the local inhabitants. They can alter the food web and the flow of energy by doing so. They can even change the very material on which the ecosystem is built, by turning sandy sea floors muddy! Invasive species can (and have) changed many aspects of a benthic ecosystem, and the plastics only increase their ability to spread globally. Invasive species are important to humans in many ways, and can be quantified economically. For instance, they can put pressures on local commercial stocks of fish or bivalve species, thus reducing yearly harvest of seafood.

Plastics alter ecosystems via ingestion

Thinking back to the presence of microplastics in the marine world, seafloor-dwelling animals, such as mussels, readily consume the small bits of plastic when filtering the water for plankton and other microscopic creatures. The majority of plastics that these mussels eat are microscopic fibers from our clothing. This is harmful to the animal that eats the small plastic bits as the plastic has been reported to cause harmful blockages or become incorporated into the circulatory system, for instance. This could therefore lead to increased mortality rates amongst the consumers of the plastics. This also directly affects us as consumers, for we generally eat benthic animals, such as mussels, without removing their stomachs. That means, whatever the mussel eats for dinner, a human eats for dinner.

Much research needs to be done to understand the new role of microplastics in the sea floor ecosystem. What is the abundance of microplastics on the seafloor? How will they alter the food chain on the sea floor and how will this affect the lifecycles of benthic animals? These are all important questions to be answered as microplastics become increasingly prevalent on the bottom of the ocean.

What can we do?

It may seem a haunting or bleak image of plastic consumption and its effects on our local environments. But, the first step toward devising solutions is through education (like reading this blog). Plastic production is hinged on our consumption, so an easy place to start is by reducing (or eliminating) single- use plastic consumption and choosing more sustainable alternatives to your consumed goods. You could also get involved in organizations such as 5Gyres that focus on working with citizens, politicians, and corporations to reduce plastics production and pollution. You could participate in local beach clean up efforts. As we are the sources, we should be the ones to reduce our plastic footprint.

In Summary

Plastics provide a home to many, but their very presence affects benthic habitats and how the ecosystem functions. It can lead to the colonization of soft seafloors by hard-substrate-loving animals, potentially leading to local extinction of certain soft-sediment-loving species. Plastics can provide long- term rafting opportunities to potentially invasive species, which affects many aspects of the local ecosystem and our commercial seafood industry. They pose a threat to marine animal and human health once broken down into microplastics. And so, we must reduce our plastic footprint by being more conscious consumers of plastic goods. We must work against the saying of “home sweet plastic” and return it to “home sweet home.”

Research Cited

Barnes D (2002). Invasions by marine life on plastic debris. Nature; 416: 808-809.

Carlton JT, Chapman JW, Geller JB, Miller JA, Carlton DA, McCuller MI, Treneman NC, Steves BP, Ruiz GM (2017). Tsunami-driven rafting: Transoceanic species dispersal and implications for marine biogeography. Science; 357: 1402-1406.

Cole M, Lindeque P, Halsband C, Galloway T (2011). Microplastics as contaminants in the marine environment: A review. Marine Pollution Bulletin; 62:2588-2597.

Galloway T, Cole M, Lewis C (2017). Interactions of microplastic debris throughout the marine ecosystem. Nature Ecology and Evolution; 1:0116.  doi:10.1038/s41559-017-0116.

Geyer R, Jambeck J, Law KL (2017). Production, use, and fate of all plastics ever made. Science Advances; 3:e1700782.

Katsanevakis S, Verriopoulos G, Nicolaidou A, Thessalou-Legaki M (2007). Effects of marine litter on the benthic megafauna of coastal soft bottoms: A manipulative field experiment. Marine Pollution Bulletin; 54: 771-778. 


Is jellyfish cuisine a viable population management solution?

Giant Jellyfish clogging fishing nets in Japan. Photo by Shin-ichi Uve

Benthic ecology blog post by: Leah Werner

As man’s reach extends across the planet to the detriment of millions of species, select species are taking full advantage of the new territories and food resources. Jellyfish are one of these. And as a consequence, a new picture of their dominance is emerging. Local jellyfish blooms are increasing in numerous locations across the globe. These growing numbers can lead to many deleterious consequences for fishing and aquaculture: killing farmed fish, fouling net pens and causing fish gill disorders, capsizing small fishing vessels, damaging fishing nets, contaminating catches, and reducing commercial fisheries through predation and competition. They clog intakes to the detriment of various industries (desalinization and power plants, mining, military operations, shipping). They cause injury and even death to beachgoers causing loss in tourism revenue and beach closures. To the scientists, jellyfish invasions serve as an indication that oceans are suffering at a magnitude not fully understood.

A suite of human‐induced stresses including overfishing, increased availability of hard substrate in coastal systems through habitat modification, invasive species introductions, eutrophication, and climate change appear to be increasing jellyfish blooms in both frequency and magnitude (Richardson et al. 2009). Although a lack of data makes it difficult for scientists to conclusively say whether jellyfish outbreaks are increasing on a global scale, there have been numerous occurrences of localized increases reported off the coasts of all seven continents.

Although one might think they know a jellyfish when they see one, thousands of species fall under the umbrella of term “jellyfish” – similar only in their body composition and ability to undergo population blooms. Their shared attributes enable them to take advantage and even thrive in highly disturbed and variable environments. Jellyfish are able to reproduce both asexually (offspring that arise from a single organism) and sexually (offspring come from two parents). Although reproduction varies among species, most coastal jellyfish have a benthic larvae stage known as ‘polyps’, where the larvae are attached to the seafloor. These polyps bud more polyps, and many jellyfish can come from a single polyp. Swimming jellyfish (medusae) reproduce sexually and produce many larvae which settle on the seafloor to become polyps. Therefore, jellyfish are able to multiply quickly relative to competitors, which serves to their favor after a disturbance such as bottom trawling wipes out entire communities from the seafloor. Jellyfish are also fierce predators who consume both zooplankton (also consumed by fish), ichthyoplankton (fish eggs and larvae) and small fish; thus their increasing numbers limit fish by exploiting their food source and direct predation.

There has been increasing pressure to find innovative uses for jellyfish as a means of controlling their populations – from utilizing jellyfish for medicinal products to developing microplastics filters from jellyfish mucus. However many of the proposed solutions do not require large amounts of jellyfish.

What to do? Open your mouth. Indeed, the largest use of jellyfish is human consumption, and jellyfish fisheries are expanding worldwide as a result.

Consumption of invasive or nuisance species as a means of population control is not a novel idea. Albeit not common menu items, the markets for fishing invasive species such as Asian carp in the Great Lakes and lionfish in the Caribbean Sea and western Atlantic Ocean are steadily growing. And what more – China and other Asian countries have already perfected the art of jellyfish cuisine. Jellyfish has been consumed both regularly as well as on special occasion such as holidays, weddings and other celebrations in China since 300 AD. Malaysia and Indonesia established jellyfish fisheries around the mid‐twentieth century and Thailand and the Philippines followed suite in the 1970s. Within the last few decades, various Asian countries have initiated jellyfish fisheries, and to keep up with the growing demand, jellyfish fisheries have more recently expanded around the globe, primarily for export to China and Japan.

Although catch data for jellyfish remains scant as many countries fishing for jellyfish do not report their catches to the Food and Agricultural Organization of the United Nations, a recent estimate indicated 19 nations are currently fishing for jellyfish with estimated landings of at least 900,000 metric tons annually as of 2016. And why not? Exploiting an unwanted, abundant resource that is wreaking havoc on industry and the environment seems justified. The demand placed on exploited fish such as Atlantic cod and bluefish tuna is causing a risk for irreversible recovery. It seems crucial to alleviate that demand towards a ‘nuisance’ species. Moreover, jellyfish often contain collagen, which can be used to treat arthritis and visible signs of ageing, as well as glycoproteins, used in cosmetics, and food additives and in drug manufacturing.

A recent paper, “We should not assume that fishing jellyfish will solve our jellyfish problem” published in the ICES Journal of Marine Science, explores the debate behind the expansion of jellyfish fisheries as an adequate means to control their populations. While it may be enticing to exploit this growing unwanted resource for consumption, it might not be the most cost‐effective or ecologically‐sound option. Jellyfish abundance is unpredictable and populations can vary drastically from year‐to‐year making it difficult to invest in infrastructure to support the growing fishery.

Another barrier is that fishing jellyfish is only a short‐term management solution. Fishing would target medusae, free swimming, sexually reproducing jellyfish, which are derived from benthic polyps. Removing medusae from the water column won’t eliminate jellyfish from the area, as the polyps will continue to reproduce. And most attempts of eliminating polyps have been largely unsuccessful.

Even if fishing of medusae could reduce a jellyfish population, the ecological implications are unknown making it a dangerous endeavor. Despite jellyfish blooms’ trending headlines, jellyfish are largely understudied and removing them from a system could injure other species. Studies have shown jellyfishes’ versatile role in an ecosystem, including acting as “habitats” and nurseries for juvenile fish and as agents for carbon sequestration. Jellyfish have been found to prey on dominant species, enabling less competitive species access to resources thereby increasing biodiversity.

While there is optimism in the developing market of jellyfish, we should be careful not to see this as an all‐ encompassing solution. Although the apparent drivers of jellyfish blooms, such as overfishing and climate change, are global issues, their effects vary widely on a local level. Consequently, management of jellyfish blooms should be made on a case‐by‐ case basis. Given that the drivers of the jellyfish blooms appear to be inter‐correlated and act synergistically, a straightforward solution might not be intuitive.

Before investing and expanding jellyfish fisheries on a global scale, a word of caution is advised. There are far too many unknowns to assume that fishing jellyfish will only reduce jellyfish numbers without impacting the wider ecosystem. Additional research is needed to explore jellyfish life cycles and their larger roles in the marine ecosystem. And most importantly, the problem will continue to exacerbate itself unless we take a step to learn from and combat the human‐led drivers that initiated the problem in the first place.


The Key to Successfully Conserving Our Salt Marshes

Benthic Ecology Blog Post by: Natalie Posdalljian

Coastal ecosystems are suffering rapid decline and increased degradation as a result of human disturbances. Finding successful solutions for conserving and protecting important habitats is critical. Formerly perceived as coastal ‘wastelands’, salt marshes are one of the most underappreciated coastal systems. In addition to housing a wide variety of flora and fauna, salt marshes are extremely productive coastal systems that serve as a barrier between land and sea. Extremely vulnerable to human activity, tidal marshes are in trouble and efforts worldwide have ramped up to stave decline. Restoration, or returning habitats back to a healthy condition, is a promising yet challenging method used for conserving salt marshes. Successful restoration requires effective initial rehabilitation of the habitat and long-term persistence, stability, and resiliency in the face of future natural and human disturbances. Restoration isn’t always successful and attempts could result in partial recovery or complete failure, where restored conditions do not match those of natural marshes. A new study might have found the key to amplifying salt marsh restoration success; fostering mutual interactions between species.

What Are Salt Marshes?

Continuously flooded and drained by tides, salt marshes are found worldwide, along every U.S. shoreline and most commonly within estuaries. Salt marshes facilitate complex food webs including primary producers (i.e. salt-tolerant grasses, vascular plants, phytoplankton, etc.), primary consumers (i.e. zooplankton, molluscs, insects, etc.), and secondary consumers (i.e. birds and fish). What makes salt marshes particularly unique is their existence between land and sea, linking marine habitats and organisms to their terrestrial neighbors directly inland.

Why Are Salt Marshes Important?

Salt marshes provide a wealth of services, referred to as ecosystem services that make them extremely valuable habitats to conserve. Salt marshes serve as nursery habitats for a variety of marine life, including more than 75 percent of fishery species. Wading birds feed in these productive habitats while migratory birds use salt marshes as stopping points on their routes. Salt marshes serve as a buffer between land and sea, filtering nutrients, run-off, and heavy metals, even shielding coastal areas from storm surge, flood, and erosion. These transitional ecosystems are also vital in combating climate change by sequestering carbon in our atmosphere.

What Natural and Anthropogenic Disturbances Do Salt Marshes Face?

Salt marshes occupy prime coastal real estate sharing the shoreline with around 10 percent of the world’s population or nearly 600 million people, according to the United Nations. This makes marshes extremely prone to human disturbances, especially habitat loss seen from land reclamation for urban development and agriculture. Being surrounded by these areas leads to an influx of nutrients in the form of sewage, agricultural run-off, and industrial waste.

Enrichment by excess nutrients causes shift in vegetation structure and provides non-native organisms the opportunity to invade and thrive in salt marshes. Invasive species like the common reed in Narragansett Bay, outcompete indigenous reeds and marsh grasses eventually leading to decline of wildlife and plant diversity, species abundance, and in the worst-case scenario, extinction,

Overfishing is often also blamed for degradation of salt marsh habitats. Loss of top predators like cod, striped bass, and blue crabs has been linked to collapse of salt marshes. With top predators being commercially and recreationally fished out, voracious herbivores like marsh crabs take over and destroy cordgrass, an essential wetland plant. The consumers who are being overfished play an important role in regulating these communities and removing them out of a system could lead to its collapse.

Climate change, and associated sea level rise, also negatively affect salt marshes. Distribution of plants and animals within marshes are based on various factors, especially tolerance of specific organisms to salinity and wetness. Temporary or permanent flooding from sea level rise could drown certain plants, not giving them enough time to move further inland in order to survive, and lead to erosion of the marsh into open water.

How Can We Conserve Salt Marshes?

As salt marshes are reinterpreted, their ecosystem services become better understood.  This results in an increase of conservation efforts to the tune of 1 billion US$ worldwide. Efforts include proper management of existing marshes, introduction of legislation to protect ecologically important habitats, reduction of intense development along the coast, and restoration of damaged marshes.

Two ideologies exist when considering options for restoring salt marshes.  One option acknowledges that humans have done enough damage. Perhaps habitats are better off with no additional anthropogenic interference and only require time and space to recover naturally. The second option emphasizes restoring degraded habitats back to their natural state.  Restoration efforts include removing non-native species, removing dikes, levees, etc. to restore natural tidal influences, and establishment of a single foundation species to facilitate the return of natural biodiversity. Although great in theory, restoration is logistically difficult, expensive, labor- intensive, and not always successful.

So, What Is the Key to Restoration Success?

Positive interactions are relationships between different species that result in better growth, reproduction and/or survival for at least one species involved in the interaction without negatively affecting the other species. Several studies have found that positive interactions reduce physical stress and increase resource availability within salt marshes. For example, mussels stabilize and fertilize soil that benefit the cordgrass, a primary foundation species.

Cordgrass traps sediments, creates low-marsh habitats, provides site for mussels to attach, and contribute dead plant matter to their diet. Positive interactions, such as those between mussels and cordgrass, play an important role in the function and stability of marshes. However, consideration of these implications and the potential of harnessing these interactions to improve salt marsh restoration has been limited thus far. In fact, a survey found that only 1 out of 25 restoration agencies in the U.S. considered positive interactions within their restoration design.

A group of scientist from all over the world set out to investigate whether positive interactions between cordgrass and mussels can increase restoration success in degraded U.S. salt marshes. They found that co-transplanted mussels, those transplanted with cordgrass, increased nutrients and reduced sulphide stress for local cordgrass. In return, this increased cordgrass growth and expansion throughout the habitat. Then the scientists simulated a disturbance and removed above-ground vegetation and mussels. They found that co-transplanted cordgrass had three times the survival rate compared to cordgrass that was transplanted without mussels. Not only did co-transplantation enhance cordgrass and mussel growth, it also improved resiliency of the foundation species to disturbance. Overall, the study found that mussels amplified cordgrass recolonization and resilience across broad spatial and temporal scales and utilizing these relationships could improve restoration success.

Integrating positive interactions is a simple yet promising tool to incorporate into restoration design across all coastal ecosystems. This tool has the potential to improve initial restoration success and also long-term resiliency, especially in the face of disturbances that these habitats will no doubt face in coming decades. This study contributed yet another method into the restoration toolbox that managers and policymakers should utilize in conjecture with other established methods to rehabilitate and reconstruct coastal ecosystems.

This newspaper article was inspired by NPR science and the following study,


New inhabitants of seafloor and shoreline habitats in Central California surprise researchers, provide new insight into valuable coastline

Benthic Ecology Blog Post by Tyler Hee

Researchers have found surprising abundances of non-native species in several intertidal habitats (the area of shore exposed at low-tide and submerged at high-tide) and subtidal habitats (the shallow are just below the intertidal) along the important, exposed coastline of Central California. Watersipora a non-native group of bryozoans, or marine invertebrates that live in colonies, and are usually found in calmer waters but was found extensively distributed during the surveys. Additionally, Caulacanthus ustulatu, a species of red turf alga that can form dense patches and outcompete native algae species was found at several survey sites.

Generally, more invasive or non-native species of marine organisms are reported in harbors, bays, and estuaries than in wave-battered, open-coast habitats like those found along Central California. Perhaps due to this difference, there is less concern and more infrequent management efforts for non-natives along the coast of Central California. This indifference however, should be addressed as the subject area of this study is extremely important both ecologically and economicall.

What’s so special about coastal Central California?

The area studied by Zabin et al. covered 275 km, stretching from Pt. Reyes located north of San Francisco Bay southward to Ventura Rocks just south of Monterey Bay. These waters include the Greater Farallones National Marine Sanctuary (GFNMS) and the Monterey Bay National Marine Sanctuary (MBNMS). From estuarine wetlands to rocky shores to kelp forests and open ocean, these two sanctuaries protect important aquatic habitats. These habitats are important for a wide range of fish and marine mammals – some of which are endangered or threatened – that call the waters off Central California home.

These coastal waters, rich with life, are important not only for the animals and other organisms that live there but for the human communities in the area. GFNMS supports 508 commercial and recreational fishing jobs each year with a combined fisheries worth of $53.2 million. Even more staggering, the non-consumptive uses of GFNMS, namely tourism and related activities, supports 1,131 jobs and generates an output of $145.8 million. Not to be outdone, commercial and recreation fisheries in MBNMS annually supports 1,755 jobs and creates an output of $194.8 million. The non-consumptive uses of MBNMS support 542 jobs and generates and output of  $69.4 million each year.

Clearly, the areas examined by Zabin et al. are both diverse, ecologically important marine habitats as well as extremely important natural resources that support vital coastal economies for California. Thus, understanding possible trends and developments of potential invasions by non- native species is crucial to the long-term ecological and economic health of the region.

Non-native species found in unexpected areas
The team of scientists surveyed 20 areas in the 275 km stretch of coast from 2014-2015. They looked at an array of intertidal and subtidal sites and recorded the number of and percent of sea floor coverage by non-native species at the study sites. Upon completion of their study, the team found that while numbers of non-native species in these exposed coastal systems are not as abundant across the entire range as in sheltered areas such as harbors, there were some species that were much more common than expected.

The small colonial group of animals, Watersipora, was found in 45% of the study area at one site and 26% lower in the tidal area at the same site. Additionally, the red turf alga Caulacanthus ustulatus, which may compete with native turf alga, was found to cover nearly 20% of the shoreline at one study site.

Despite limited findings, big implications about potential vulnerability in Central California
This study marks the first recorded account of Watersipora in the cooler, wave-exposed waters of Central California. The spread of these invertebrates into waters thought to be too cool and exposed to wave shock could be an important indicator of broader environmental changes to these ecosystems such as warming ocean conditions or adaptation by the non-native animal.

The data collected on the red turf alga, Caulacanthus ustulatus, is the first numerical report for the non-native seaweed. The high coverage at one of the teams Central California study sites is of interest because of the observed impacts this non-native alga has had on native algae and invertebrates in Southern California waters.

The observation of these non-native species in the coastal habitats of Central California merits further attention. There is currently insufficient data to fully understand what trends may or may not be occurring to allow these non-native species to spread to areas previously believed to be highly resistant to such expansion. There is also no information on what impact or damage may be occurring as these species being to occur in new habitats. Further study is needed to ensure effective management decisions of this ecologically and economically important area.

What’s next?

The novel observation of Watersipora and Caulacanthus ustulatus in the typically cooler, open- coast systems of Central California at unexpected abundances may result from by the species or may signal broader regime shifts. Similar to the supposed northward range expansion of tuna crabs off Southern California, the observation of these non-native species in new territory may be linked to changing ocean conditions, namely warmer water. The causes behind these occurrences should be examined because they may help to further explain the changing ecosystem structures of other Central and Northern California habitats like the spike in purple urchins and loss of kelp beds. Thus, before conservation and management decisions can be made in response to changing conditions, we must first ask “what’s driving these changes?” To make decisions before that question is answered puts the ecosystem health and economic value of the Central California coast area in unnecessary jeopardy.


Laura Smith-Spark. Red Tuna Crabs Wash Up on San Diego Beaches. 17 June 2015.

Office of National Marine Sanctuaries. Gulf of Farallones National Marine Sanctuary: Commercial Fisheries – Economic Summary. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Office of National Marine Sanctuaries. 2014. Economic Contributions from Recreational Fishing in Greater Farallones National Marine Sanctuary, 2010 – 2012. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Office of National Marine Sanctuaries. Monterey Bay National Marine Sanctuary: Commercial Fisheries – Executive Summary. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Office of National Marine Sanctuaries. 2014. Economic Contributions from Recreational Fishing in Monterey Bay National Marine Sanctuary, 2010 – 2012. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Office of National Marine Sanctuaries. Dec 2015. Socioeconomics of California’s Northern Central Coast Region: Economic contributions from non-consumptive use. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Swierts, T., & Vermeij, M. J. (2016). Competitive interactions between corals and turf algae depend on coral colony form. PeerJ, 4, e1984.

Zabin, C. J., Marraffini, M., Lonhart, S. I., McCann, L., Ceballos, L., King, C., … & Ruiz, G. M. (2018). Non-native species colonization of highly diverse, wave swept outer coast habitats in Central California. Marine Biology, 165(2), 31.


Are we changing coral reefs and the ecosystem services they provide?

Benthic Ecology Blog Post by Travis Courtney

Coral reefs provide about half a billion people around the world with food, coastal protection, building materials, and/or income (1). Thirty million of those people live on atolls and are nearly entirely dependent on the ecosystem services provided by coral reefs for their livelihood (1).

Despite their great importance, coral cover has declined in recent decades primarily due to a combination of increasing global seawater temperatures and local overfishing, pollution, and land use changes (2,3). Corals are the dominant reef builders making these losses in coral cover particularly alarming for the people depending on coral reef ecosystem services. A recent study (4) led by Jennifer Smith at the Scripps Institution of Oceanography and published in the scientific journal Proceedings of the Royal Society B supports these alarming concerns with the finding that human impacts on coral reefs across the tropical Pacific Ocean may be negatively impacting the very ecosystem services we depend on.

An example of an inhabited island surrounded by a coral reef (5).

The team of researchers explored local human impacts on coral reefs by comparing coral reefs at 450 sites from 56 islands spanning 50° of latitude over the last 10 years. They looked at both inhabited islands and remote uninhabited islands to test whether coral reefs around islands with human populations were different from coral reefs surrounding uninhabited islands. The scuba diving researchers took over 6500 photos of the coral reef seafloor and analyzed them using computer software to determine the total proportion of corals and different types of algae at every reef location. By looking at the abundances of the different reef building corals and algae relative to the non-reef building algae species, they could test whether humans were potentially changing the abilities of coral reefs to not only grow, but also recover from disturbances like elevated temperature stress and storm activity too.

The researchers recorded 37% fewer reef-building corals and 40% fewer calcifying algae on inhabited island reefs compared to uninhabited island reefs. This striking difference in reef- building species led the researchers to conclude that human populations are likely decreasing the capacity of coral reefs to grow. Because coral reefs have many organisms living on the seafloor, the researchers underscore the importance of additionally monitoring other coral reef organisms to better understand how interactions might affect coral reef responses to future change. Among these other organisms, turf algae and calcifying algae help paint a better picture of what reefs might look like in the future. Turf algae prevent new corals from settling onto the reef and directly compete against older established corals by forming turf-like mats on the reef bottom.On the other hand, calcifying coralline algae cement the hard-structure of the reef together and help new corals settle onto the reef.

The researchers found that across all of their sites, there was 50% more turf algae and 40% fewer reef-building coralline algae on inhabited island reefs than uninhabited island reefs. Increased turf algae and decreased coralline algae on inhabited island reefs both have the same effect of decreasing the ability of new corals to settle onto the reef. This suggests that local-scale human impacts may reduce the ability of coral populations to recover following coral loss from disturbances such as elevated seawater temperatures and storm activity.

Reducing fishing pressure of herbivorous fishes such as the above parrotfish may help promote coral reef health(6).

What local-scale impacts are causing these changes in coral reef communities on inhabited islands? The researchers suggest that fishing of algae-eating fishes might be causing increases in turf algae on reef environments, but what role do nutrients and other local effects have on coral reef communities? Understanding these questions may help us develop effective policies to increase the overall capacity of coral reefs to continue growing and providing the ecosystem services that so many people depend on.

At the local level, reducing local fishing pressure may help sustain fish populations that eat turf algae to recruit new corals on reefs near human populations. Meanwhile, globally decreasing greenhouse gas emissions will lessen the rise of ocean temperatures that otherwise threaten coral health. If we can change the way we interact with coral reefs and our planet, perhaps we can in turn help to support the very ecosystem services we depend on.

The study by Jennifer Smith and colleagues can be found here:

1. /MarineEcossstemsBranchUnits/TheCoralReefUnit/CoralReefs-ValuableandVulnerable/tabid/129878/Default.aspx

  1. Gardner, T. A., Côté, I. M., Gill, J. A., Grant, A., & Watkinson, A. R. (2003). Long-term region-wide declines in Caribbean corals. Science, 301(5635), 958-960.
  2. Bruno, J. F., & Selig, E. R. (2007). Regional decline of coral cover in the Indo-Pacific: timing, extent, and subregional comparisons. PloS one, 2(8),
  3. Smith, J. E., Brainard, R., Carter, A., Grillo, S., Edwards, C., Harris, J., … & Vroom, P. S. (2016, January). Re- evaluating the health of coral reef communities: baselines and evidence for human impacts across the central Pacific. In Proc. R. Soc. B (Vol. 283, No. 1822, p. 20151985). The Royal
  4. Image from <>.
  5. Image from: Jackson, J., Donovan, M., Cramer, K., & Lam, V. (2014). Status and trends of Caribbean coral reefs: 1970-2012. Global Coral Reef Monitoring


No Sea Ice? No Problem! How deep Arctic ecosystems may benefit from our changing climate

Benthic Ecology Blog Post by Morgan Ziegenhorn

When people think of the Arctic, the first thing that comes to mind is probably a polar bear sitting on a piece of ever-shrinking ice. News about polar regions is rarely good, especially when it comes to scientific discoveries—we hear that the ice is diminishing, that the animals are losing habitat, and that rapid change is occurring. While all of these are true, there’s more to our polar climates than meets the eye. The Arctic Ocean is home to the polar bear, but it’s also home to a rich diversity of species that live in deeper water and along the ocean bottom. A recent paper on the Canadian Arctic by Anni Makela and her colleagues at University of Aberdeen in the United Kingdom suggests that in some of these benthic habitats, diversity and productivity will be maintained and possibly even increase as the Arctic warms and sea ice is lost.

Map of the Canadian Arctic, showing the locations of satudy for Makela et al (5).

What’s a benthic habitat like?

Benthic habitats are those that sit along the ocean floor. The world of benthic organisms is very different from ours, but at a basic level they need the same thing we do to survive: food. Much of this food is provided via phytoplankton that live in the surface ocean and require sunlight and nutrients to create energy (termed ‘primary productivity’) through photosynthesis, like many of the land plants we’re more familiar with. When phytoplankton sink down to the ocean floor, they become food for benthic species.

Productivity, diversity, and food chains

The more food a habitat receives, the greater number of individuals and species it can support (one measure of biodiversity). And in general, the greater biodiversity of a system, the better the chance of its survival.

Systems with greater productivity also usually have shorter food chains. Most people are familiar with the idea of a food chain—the grass creates energy via sunlight and nutrients, the rabbit eats the grass, and the wolf eats the rabbit. What’s less familiar is that the energy transferred diminishes with each consumer (i.e. at each “trophic level”). The rabbit doesn’t receive all of the energy created by the grass; the wolf receives even less. For this reason, shorter food chains often mean more energy reaches the animals we usually think about, such as fish, mammals, and sea birds.

Open water and sea ice

In terms of benthic food sources, the Arctic ocean is a special case—here, much of the surface water is covered in ice, which limits the light phytoplankton receive. This makes it more difficult for them to create energy. For this reason, areas of open water (‘polynyas’) are particularly productive. But there is another piece to this puzzle, which has sparked debate over Arctic benthic systems. Sinking algae that lives on the bottom of the sea ice can also be an important source of food for benthic animals. This begs the question, which is more important for a diverse, productive benthic system? The open water, or the sea ice?

Algae vs. phytoplankton

In 2017, Anni Makaela and her colleagues published a paper focused on two open water polynyas in the Arctic Ocean: the North Water Polynya (NOW), which is the biggest and most productive polynya in the northern hemisphere, and the Lancaster Sound Polynya (LS), which is smaller and where sea ice (and associated algae) was previously supposed to contribute more to the diets of benthic species. Both polynyas occur in deep sea sites, which have not been studied as often as coastal/more shallow locations. In their study, these scientists found that benthic organisms in both systems depended mostly on phytoplankton for their food, and that sea ice algae was a prevalent food source only for very mobile organisms who could easily get to it (it falls irregularly to the ocean floor).

The NOW polynya supported a wider range of organisms and shorter trophic chains than the LS polynya, and both were more productive than expected. This suggests that, at least in some cases, deep benthic habitats can be even more productive than their shallow counterparts!

Photo of an Arctic benthic crusteacean, the snow crab (left) and an Arctic benthic bivalve, a mollusk (right) Photos adapted from the Arctic Ocean Diversity database.

The study also found that the smaller polynya was dominated by bivalves (clams, mussels, mollusks) whereas the larger was dominated by crustaceans (crabs, lobsters). They predicted that this was mainly due to differences in current speed—bivalves feed by straining food out of the water, and faster currents aid this process. In some cases, species fed on different prey at each of the two polynyas, which suggests an ability to adjust to changes (i.e., resilience in the face of the changing Arctic Ocean).

What does it all mean?

With global warming, the Arctic Ocean is one of the fastest evolving environments on our planet. Some models predict it will be free of summer ice entirely as soon as 2040. Though this will have major negative impacts on many Arctic species, this study suggests that benthic organisms may reap a positive benefit from increased open water. Additionally, these deep water systems being even more productive than previous studies suggested may change our understanding of the relationship between ocean depth and productivity (it has generally been supposed that the deeper the benthic habitat, the less productive).

How do we study Arctic benthic habitats…

This study provided one of the first examinations of the benthic ecosystem structure for a deep ocean Arctic polynya—but how did the scientists manage it?

To determine what species were at their sites, the authors took large sediment cores. This is a process that involves the removal of a chunk of the ocean floor, which can then be brought back to the lab and examined to determine the number and species of animals present.

To study the food chains and dependence of the organisms on sea ice algae/phytoplankton, this study used stable isotope analysis. This complex process is not so difficult to understand as its name suggests. Essentially, it works through the idea of “you are what you eat” by using carbon and nitrogen to trace the path of food chains through organisms. The ratio of carbon isotopes (carbon atoms with different numbers of neutrons) remains consistent as you travel up a food chain and allows scientists to identify the original food source. In contrast, the ratio of nitrogen isotopes changes at each trophic level. Combining these two via a process called mixed modelling makes it possible to construct food chains and food webs (interconnected food chains) that show who eats who, and at what trophic level.

and why do we care?

As nice as it is to hear a positive climate change effect, this story is, at its base, about an ocean that most of us will never go to, about organisms that we rarely think of, in depths that we couldn’t survive at. You might think, how could something so remote be connected to my life?

But it is. Many of the Arctic species whose survival we are invested in, such as gray whales and walruses, rely on food from benthic ecosystems like the ones studied in this paper. Arctic sea birds an

A general marine Arctic food web, courtesy of Darnis et al. (2)Facebook pages and laptop backgrounds, will be successful in their changing habitat, it at least may lighten some of their burden.

d seals dive to eat fish that feed on benthic crustaceans. The polar bears, on their thinning ice, hunt these seals. Because we care about the success and future of these species, we have to care about the future of their food.

And that’s how a story that at first seems interesting, but on the whole unimportant, can in fact have a great impact. As the sea ice melts, these polynyas grow larger and potentially more productive and diverse. In this way they provide a feasting ground for many of the species we’re invested in. As food chains shorten, more energy will reach higher trophic levels, where organisms such as the walrus and the polar bear sit. While this isn’t enough to suggest that the animals we care about, the ones whose videos fill our Facebook pages and laptop backgrounds, will be successful in their changing habitat, it at least may lighten some of their burden.

The ocean feeds us, too

Several Arctic fish species that people consume, especially Arctic peoples, rely on benthic production. As the ocean current changes, the LS polynya could no longer support bivalves and might instead support mostly crustaceans. It’s hard to say what the ramifications of this are but understanding them is important for marine Arctic species and the diets of people both in the Arctic and worldwide.

Hardly the end of the story

Makela and her colleagues made some interesting discoveries, but there’s still much that hasn’t been uncovered. Though I mentioned that the future may mean less bivalves (bad news for the organisms that eat them), this study hasn’t concluded whether shifts like this may occur. The authors focused on summer conditions, while in truth, conditions in other seasons are equally important—it’s possible sea ice may play a greater role in non-summer months. Studying the deep ocean remains difficult, and there are still questions about what we might see in other spots of the deep Arctic, especially ones that have been historically less productive. As nice as it is to hear that the Arctic benthos may be benefitting from the loss of sea ice, further study is required to say whether or not this is the case on a larger scale.

Other factors besides ice come into play as well. Temperature, salinity, and ocean mixing rates can all affect productivity levels. It’s important to get the whole story before we can make the claim that Arctic production may increase with climate change, and that some ecosystems will reap a positive benefit from global warming.

But they might.

For today, at least, I’ll take the win.


  1. Cochrane, Sabine KJ, et al. “Benthic macrofauna and productivity regimes in the Barents Sea—ecological implications in a changing Arctic.” Journal of Sea Research4 (2009): 222-233.
  2. Darnis, Gérald, et al. “Current state and trends in Canadian Arctic marine ecosystems: II. Heterotrophic food web, pelagic-benthic coupling, and biodiversity.” Climatic Change1 (2012): 179-205.
  3. Hobson, Keith A., William G. Ambrose Jr, and Paul E. Renaud. “Sources of primary production, benthic-pelagic coupling, and trophic relationships within the Northeast Water Polynya: insights from δ 13 C and δ 15 N analysis.” Marine Ecology Progress Series(1995): 1-10.
  4. Krupnik, Igor, and Dyanna Jolly. The Earth Is Faster Now: Indigenous Observations of Arctic Environmental Change. Frontiers in Polar Social Science. Arctic Research Consortium of the United States, 3535 College Road, Suite 101, Fairbanks, AK 99709, 2002.
  5. Mäkelä, Anni, Ursula Witte, and Philippe Archambault. “Benthic macroinfaunal community structure, resource utilisation and trophic relationships in two Canadian Arctic Archipelago polynyas.” PloS one8 (2017): e0183034.
  6. Moore, Sue E., Jacqueline M. Grebmeier, and Jeremy R. Davies. “Gray whale distribution relative to forage habitat in the northern Bering Sea: current conditions and retrospective summary.” Canadian Journal of Zoology4 (2003): 734-742.
  7. Odate, Tsuneo, et al. “Temporal and spatial patterns in the surface-water biomass of phytoplankton in the North Water.” Deep Sea Research Part II: Topical Studies in Oceanography22-23 (2002): 4947-4958.
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Loss of Mexico’s Valuable Mangrove Forests

Benthic Ecology Blog Post by Madelin Andersen

Mangroves are marine trees that form coastal wetlands known as mangrove forests and can be found around the world in tropical and sub-tropical climates. Mangroves have evolved to survive in coastal wetland environments where the salt and oxygen poor soil makes it impossible for other plants to live. Mangroves thrive in these conditions and are able to engineer ecosystems and provide food to numerous marine and terrestrial species.  Mangroves also provide human society with ecosystem services which are valued at US $1.9 billion world-wide annually. Mexico is one of the countries with the most mangroves in the world, but it is also undergoing some of the most rapid loss and destruction of its mangrove forests.

A mangrove forest in Mexico

Mexico’s mangroves provide ecosystem services that benefit coastal communities and the national economy. The ecosystem services provided by mangroves in Mexico include habitat creation for commercially important species, protection from hurricanes, natural beauty, and carbon storage and sequestration. These ecosystem services benefit Mexico’s coastal communities, fisheries, and the Mexican economy as a whole. Scientists at Scripps Institution of Oceanography estimate that collectively, the ecosystem services provided by Mexico’s mangroves are worth US $100,000 dollars per hectare (2.4 acres) per year, and the 700,000 hectares of mangroves in Mexico contribute an estimated US $70 billion dollars to Mexico’s national economy every year. Despite their usefulness Mexico’s mangroves are being destroyed at an alarming rate, resulting in a loss of the ecosystem services that only mature mangrove forests can provide.

Commercially important fish rely on mangrove root systems for habitat

A major ecosystem service provided by these mangrove forests is the habitat they build for many commercially important species including fish and crabs, who live in the complex root network of mangrove forests. A study on the economic importance of mangroves for fisheries in the Gulf of California was conducted by researchers at Scripps Institution of Oceanography. They found that fishery yield landings, or catches, are positively correlated to the local abundance of mangroves. The Fishing communities in the Gulf of California rely on these mangrove-related species for their livelihood and food production. According to researchers the ecosystem service mangroves provide to fisheries not only benefits local communities, but makes a significant contribution to Mexico’s developing economy and should not be overlooked.  The authors also warn that in 30 years the destruction of one hectare of mangrove fringe would cost local economies approximately US $605,290 when you take into account what they provide in terms of monetary value to fisheries.

Mexico’s mangrove coverage is diminishing due to deforestation, affecting coastal communities and the Mexican economy. The reasons why mangroves are being destroyed include logging, agriculture, and megatourism. At the current rate of deforestation in Mexico, Mexico may lose up to half of its mangroves in 50 years. Mangrove forests cannot just regrow quickly. It will take time for mangroves to reach their full potential as ecosystem service providers. The reality of the loss of Mexico’s mangroves is devastating for the Mexican economy, coastal communities, and individuals. The loss of mangrove ecosystems from deforestation has been described as irreversible to fisheries. Ecosystem-based management needs to take into account that fisheries rely on mangroves, and therefore food production and economic gain in Mexico. Mexico is a developing country, but the destruction of mangrove forest in favor of costal construction, is economically unfavorable and has irreversible consequences for fisheries.

Mangrove forests provide invaluable ecosystem service that benefit fishermen, coastal communities, and the nation’s economy. However, these ecosystem services are threatened and diminishing due to deforestation. While there have been actions taken towards replanting lost or destroyed mangrove forests, it is expensive and it will take decades before they become mature forests. “We can plant mangrove seedlings but we can’t bring back all the biodiversity and ecosystem complexity, and seldom can we bring back all the ecosystem services that they provide,” said Enric Sala, a researcher at Scripps Institute of Oceanography. It is important to take action now to protect and conserve mangrove forests in Mexico from deforestation.


Aburto, Octavio, et al. “Mangroves in the Gulf of California increase fishery yields.” Proceedings of the National Academy of Sciences 105.30 (2008): 10456-10459.

Aburto, Octavio and Jaime Rojo. “The Mangroves of Mexico – By the Numbers.” National         Graphic Voices, 12 February 2015, mangroves-of-mexico-by-numbers. Accessed 26 October 2016.

Barbier, Edward B., and Ivar Strand. “Valuing mangrove-fishery linkages–A case study of Campeche, Mexico.” Environmental and Resource Economics12.2 (1998): 151-166.

Barclay, Eliza. Mexican Resorts Destroying Mangroves, Dooming Fisheries. National  Geographic News, 21 July 2008,    Accessed 20   November, 2016.


The Missing Link in Reef Recycling

Benthic Ecology Blog Post by Michelle Loewe

What We Know

The first goal of any living thing is to stay alive. Whether it be to stay alive long enough to reproduce, or to stay alive long enough to pay off your student loans, no matter the organism, the goal is to stay alive. Of course, a very large component of staying alive is to obtain energy to sustain metabolic processes. In nature, energy, in the form of nutrients, is passed between organisms, including humans, via pathways called “food chains” and “food webs.”1 It is helpful to think of these ideas as cyclical, or as loops.

When discussing food webs and food chains, organisms are categorized into trophic level groups.Trophic levels consist of producers, consumers, detritivores and decomposers (Dunn 1993). Familiar to most of us are examples from land-based ecosystems. Producers- plants, like grasses, make food using photosynthesis. A consumer, like a rabbit, eats the grass and then another level of consumer, a fox, eats the rabbit (Dunn 1993). When the fox dies, detritivores and decomposers, organisms like worms and bacteria that eat non-living things as well as metabolic waste (detritus), decompose the remains of the fox back into the soil. Decomposing the fox remains back into the soil provides nutrients back to the grasses, cycling energy back to the lowest trophic level (Dunn 1993).

In marine systems, particularly coral reef systems, the food webs are more complex than the grass- rabbit-fox example. One reason for this complexity is the high biodiversity of coral reef systems. With a high number of species inhabiting the system like reef-building corals, herbivorous fish, crabs, lobsters, shrimp, sea turtles and sharks, there are more pathways for the transfer of energy through food webs. While we know that coral reef systems support many different species, indicating that nutrient cycling is happening in these systems, scientists haven’t known much about how energy is transferred between the corals and higher trophic levels until now.

What’s Missing?

Corals contain photosynthetic algae called zooxanthellae that live inside of each coral polyp. The zooxanthellae help the coral process nutrients and the coral provides habitat to the algae. The photosynthetic process carried out in corals transforms inorganic carbon, like carbon dioxide, into organic carbon.

This is called “carbon fixing” and makes corals known for being primary producers. Corals release this organic carbon into the surrounding water as dissolved organic matter (DOM) in the form of coral mucus. The mucus, as appetizing as it may sound, is still not accessible in this form as a food source to many reef organisms. So how are the consumers that inhabit these highly productive coral reef systems getting energy from the corals?

Scientists believe that the missing link between corals and higher-level reef consumers is none other than the detritus, or waste, of reef sponges! Reef sponges are organisms made of many cells with pores and channels that allow water to move through their bodies. Sponges can provide food to other organisms through sponge detritus and through predation on the sponge itself (Rix et al. 2018). In addition to sponge-derived food sources, scientists believe that reef sponges take up DOM produced by corals and transform it into detritus which organisms such as worms, crabs, sea stars, snails and fish can consume. Thus, reef sponges are providing a pathway for DOM to get to consumers in higher trophic levels (Rix et al. 2018).

Photos (clockwise from left): Coral –Ctenactis echinate (Charlie Vernon), Reef Sponge- Negombata magnifica (Scubaluna), Erect ropesponge- Amphimedon compressa (Jim Lyle), Brittle Star- Ophiothrix foveolate (Nick Hobgood), and Bluestriped grunt –Haemulon sciurus eating a brittle star (Jim Lyle).

The Search for Answers

To test this idea, scientists completed an experiment using stable isotope tracers. Stable isotope tracers are used to track an isotope through a metabolic pathway (Middleburg 2014). Isotopes are variations of the same element that have the same number of protons but different numbers of neutrons (Stable Isotope Principles 2018). For example, Carbon-12 (12 C) and Carbon-13 (13 C), where 13 C has one more neutron than 12 C. This gives the elements different masses. Both 12 C and 13 C are stable isotopes, which are not radioactive (Levin, class lecture). When an organism, such as a reef worm or fish, consumes its food, it is taking in carbon in several forms. Due to difference in mass, 12 C is metabolized faster than 13 C, so the ratio of 13 C to 12 C in an organism’s tissue differs as trophic level changes (Levin, class lecture). This variation with trophic level change is referred to as a stable isotope signal or signature. Scientists are able to track the signals of these isotopes from the primary producers to the consumers (Middleburg 2014). Organisms that have the same or similar 13 C signatures often share the same primary producer energy source (Levin, class lecture). Going back to our land- based example, this process is akin to testing the tissue of the fox that had consumed the rabbit and being able to determine the location or species of grass that the rabbit had eaten.

In this experiment, scientists “labelled” the test corals with Carbon-13 (13 C ) and Nitrogen-15 (15N), essentially imprinting 13 C and 15N stable isotope signatures into the corals.2 Then, after a matter of days, two species of reef sponges and their associated detritivores- two species of sea worms and one species of brittle sea star- were placed in aquarium tanks connected to the coral tanks (Rix et al. 2018). Both sets of tanks were supplied with a constant flow of fresh-pumped reef water. After several days, stable isotopic analysis was completed on the worms and brittle stars to determine if their tissues had the same 13 C and 15N signatures that was given to the corals.

When stable isotope ratios of the control organisms were compared with those of the experiment organisms, enrichment of 13 C and 15N was detected in the sponge detritivores, the worms and brittle stars, living on the sponges exposed to the labelled corals (Rix et al. 2018). This indicates that the reef sponges processed the coral mucus DOM into sponge detritus which the detritivores then consumed.


Not only was this study able to show that the organic matter produced by corals is transfered up the reef food web by sponges, but it also showed that both encrusting and massive branching sponges participate in this process (Rix et al. 2018). As discussed earlier, reef sponges provide habitat and food to many reef organisms and the results of this study have implications for the ability of reef sponges to be able to provide food to their habitants in times of food shortages. Many reef sponge inhabitants, such as brittle stars, are preyed on by reef fishes, recycling the coral-derived detritus to higher trophic levels (Rix et al. 2018). This upward movement via detritus consumption is an important component in the recycling of primary production which keeps the reef food web moving. Further study is needed to determine if there is a measurable benefit to the reef sponges for providing food and habitat to these organisms (Rix et al. 2018).

As ocean temperatures and chemistry continue to change, some organisms will be affected more than others. It is predicted that coral reefs may be particularly susceptible to warming water temperatures and increased ocean acidity, among other things. As we work to predict and plan for mitigation of these affects, there is still much that is not known about these highly diverse ecosystems. The conclusions of this study highlight the important role that reef sponges play in the reef web and provides a link between the primary producers and the consumers on coral reefs.

1 A food chain is a particular pathway that nutrients (energy) take through trophic levels (hierarchy of levels in an ecosystem). A food web is a compilation of many different food chains interconnecting with one another and including many trophic levels.
2 The nitrogen isotope tracer works similarly to the carbon isotope tracer and allows scientists to determine where an organism resides with regard to trophic level (Middleburg 2014).

Article References: **Indicates publication that this article was based upon

Dunn, Margery G. (Editor). (1989, 1993). “Exploring Your World: The Adventure of Geography.” Washington, D.C.: National Geographic Society.

Levin, Dr. Lisa. (22 February 2018). Stable Isotope Ecology. Personal lecture notes.

Middelburg, J. J. (2014). Stable isotopes dissect aquatic food webs from the top to the bottom. Biogeosciences, 11(8), 2357.

**Rix, L., de Goeij, J. M., van Oevelen, D., Struck, U., Al-Horani, F. A., Wild, C., & Naumann, M. S. (2018). Reef sponges facilitate the transfer of coral-derived organic matter to their associated fauna via the sponge loop. Marine Ecology Progress Series, 589, 85-96.

Stable Isotope Principles. (6 March 2018). Retrieved from:

Hydrothermal Vents: Incubators for Deep-Sea Skate Egg Cases!

Benthic Ecology Blog Post by Tarice Taylor

The Deep, Dark Discovery

A scientific paper published on February 8, 2018, in Scientific Reports, details the 2015 discovery and research of external egg cases belonging to the deep-sea skate species, Bathyraja spinosissima (think: cartilaginous fish related to sting rays and sharks), nestled within close range of a hydrothermal vent system. This location and discovery occurred at the Iguana-Pinguinos hydrothermal vent site, a little over a mile below the ocean’s surface in the Galapagos Rift. The team of international scientists who made the discovery were puzzled, to say the least. These scientists knew that similar egg-incubating behavior had been recorded in Cretaceous sauropod dinosaurs and the rare avian megapode, who both used volcanically heated nesting grounds to incubate their eggs, but this discovery would be the first time that scientists would witness this incubation behavior in the marine environment. This unique behavior would give scientists information not only pertaining to the behavior of one of the deepest-living sea skate species, but also to the hydrothermal vent ecosystem in which they were utilizing.

What Exactly are Hydrothermal Vents??

Deep-sea hydrothermal vent ecosystems were discovered in 1977 and can be compared to geysers, or hot springs, that span the ocean floor. Tectonic plates spread apart along the mid-ocean ridges and magma rises and cools to form new crust and volcanic mountain chains. Deep within the ocean’s crust, seawater circulates and becomes heated by the hot magma. Pressure builds, the seawater warms, and the minerals within dissolve and rise to the crust’s surface. The hot, mineral-rich water exits the ocean’s crust and cools the seawater above. As the vent minerals cool, they solidify into mineral deposits and form different vent structures which are characterized by their physical and chemical factors, like temperature, minerals and their plumes. The hottest, darkest plumes are known as black smokers, which will be mentioned again regarding the discovery of the Bathyraja spinosissima’s egg cases. Hydrothermal vent ecosystems have challenged many scientists’ views of how marine ecosystems function and even today, over forty years after their initial discovery, hydrothermal vents are still revealing unique biological and chemical processes as they interact with their surrounding environments; they have even proved to influence global geochemical cycles. Hydrothermal vents are the largest biome on Earth, but are one of the least studied ecosystems on the planet, mainly due to the fact that they are not as easily accessible as coral reefs where one would leisurely snorkel and/or dive or tide pools, next to a public beach, where countless, colorful sea creatures are wading. These hydrothermal vent ecosystems are found in the deepest and darkest depths of the ocean – most at depths of a few miles beneath the surface, far out of the reach of divers or snorkelers. In order locate and study these unique ecosystems, it takes a team of scientists skilled in operating remotely operated vehicles (ROVs) or other varieties of unmanned underwater vehicles (UUVs); it also takes time and money. The Iguana-Pinguinos hydrothermal vent site where the egg cases of the Bathyraja spinosissima were found, is located at the Galapagos Rift, part of the Galapagos Platform in the eastern Pacific, approximately 1,000km west of the coast of Ecuador. This area consists of 13 major volcanic islands, which are the famous Galapagos Islands, and also many seamounts. This particular hydrothermal vent system is approximately 1,670m to 1,690m in depth – a little more than a mile below the ocean’s surface. Creatures that live at these depths have evolved to do so. As previously mentioned, the physical and chemical factors paired with cold, dark, and nutrient-poor conditions, make this an extremely harsh environment to live in. The discovery and study of this deep-sea skate species further proves that there is a direct link between the animals that live in this environment and how they have successfully adapted to endure rough environmental conditions and maybe even conditions that are not so natural.

Deep-Sea Skate-ing Through Life

In June 2015, on a 10-day collaborative research cruise, scientists began exploring the seafloor using the ROV systems Argus and Hercules, each outfitted with an HD color video camera. The ROV landed on a ridge, which is an underwater mountain system, in the Galapagos Rift. Scientists had come to this area to specifically study the hydrothermal vent ecosystem but when they panned the ROV-mounted camera downward, they noticed something they did not expect to see: egg cases (as seen below). These egg cases, also called mermaid purses, were quite abundant

A “black smoker”, a type of hydrothermal vent, in the Galapagos Rift (left). Skate egg cases collected in the area (right). Images: Ocean Exploration Trust

in the area of view and scientists concluded that whatever was laying them had to have been using this specific site for many years, intentionally returning to it to lay their eggs. As scientists continued to scan and research the area, they continued finding the same egg cases, 157 to be exact, and concluded that this was not just one animal but the behavior of many individuals of the same species. How did they find out “who” the culprit was and “why” the odd behavior of laying egg cases near the hot, hydrothermal vents? The ROVs collected four egg cases and once they were safely brought aboard the research vessel, scientists carefully opened them to sample for molecular analysis. DNA analysis revealed that these egg cases belonged to the species Bathyraja spinosissima, one of the deepest-living sea skates but not usually known to have their egg cases in such close proximity of the vents – black smokers, to be more specific! Scientists discovered that the majority of the cases were found within 65ft of the chimney-like black smokers, which are the hottest hydrothermal vents, as aforementioned. Temperatures here can reach almost 500°! Almost 90% of egg cases found were in places where the water surrounding the vents was hotter than average. Ultimately, scientists concluded that this “strange” behavior was really an adaptive behavior to reduce incubation time. Deep-sea skates are known to have one of the longest incubation times in the animal kingdom, several years to be exact, and that this particular species was utilizing the warm water around the hydrothermal vents to decrease the amount of incubation time. But why?

Why Care About the State of the Deep-Sea Skate?

Through this discovery and research, scientists concluded that the Bathyraja spinosissimaspecies of deep-sea skate are utilizing the hydrothermal vent ecosystems as a symbiont to reduce their incubation times as they may be becoming sensitive to changes in the environment in which they inhabit. Deep-sea fishing and trawling, deep-sea mining and other natural resource exploration are inducing changes that are extensively damaging and even destroying the seafloor. Understanding the dynamics of these hydrothermal vent systems, even though they may seem “out of sight, out of mind,” may be absolutely necessary in the next steps of conservation efforts for the deep-sea and hydrothermal vent ecosystems, especially since technology for resource exploration and extraction on the ocean floor is rapidly advancing. Charles Fisher, Professor and Distinguished Senior Scholar of Biology at Penn State and an author of one of the papers referenced stated, “The deep sea is full of surprises. I’ve made hundreds of dives, both in person and virtually, to deep-sea hydrothermal vents and have never seen anything like this.” Perhaps “this,” should be deemed not just as the discovery of a unique, altered behavior of a species but also as a call-for-attention to an area of the sea where changes in the environment are imminent and that the species living there are adapting as best they can in hopes to survive anthropogenic impacts. Although a delicate creature half a world away, Bathyraja spinosissima may be telling scientists, researchers, and conservationists, through their altered behavior, that it is time to start asking questions and taking action: What can be done to mitigate these issues, especially with the advancement in deep-sea mining, mineral exploration and extraction? Are species in other benthic ecosystems that are witnessing anthropogenic threats also exhibiting adaptive behavior to changes in their environment? Even though it seems that the deep-sea skate species is exhibiting a behavior that may increase its likelihood of survival what will happen to this species if their hydrothermal vent ecosystem were to disappear completely because of anthropogenic impacts? Could they adapt then?


Cowen, Angela. Deep Sea Hydrothermal Vents: Redefining the Requirements for Life. National Geographic Society. 21 March 2013. Web. 04 March 2018.

Newsonia. Deep-Sea Skates Use Hydrothermal Vents as Egg Incubators. Web. 04 March 2018. hydrothermal-vents-as-egg-incubators/

Pelayo Salinas-de-León, Brennan Phillips, David Ebert, Mahmood Shivji, Florencia Cerutti-Pereyra, Cassandra Ruck, Charles R. Fisher, Leigh Marsh. Deep-sea hydrothermal vents as natural egg-case incubators at the Galapagos Rift. Scientific Reports, 2018; DOI: 1038/s41598-018-20046-4

Penn State. “Deep-sea fish use hydrothermal vents to incubate eggs.” Science Daily. Science Daily, 12 February 2018.


A Bad Romance-Climate Change Creates Toxic Relationship in Coral

Benthic Ecology Blog Post by Ariel Pezner

For humans and animals alike, relationships are best when they are equal. Corals are one of the best examples of a partnership in nature, though climate change may be souring their relationship beyond repair. Given the crucial role that corals play in forming and maintaining diverse and healthy coral reefs, understanding how and why this break up occurs is essential for preserving reefs for the years to come.

Coral reefs are some of the most biodiverse ecosystems on the planet, supporting nearly a quarter of the world’s marine species, despite covering less than 1% of the Earth’s surface. Though they look like rocks to the average observer, the corals that create these massive reefs are living organisms. These animals create skeletons out of calcium carbonate (the same material as limestone or chalk) covered with a thin layer of tissue, and the product of their efforts makes them one of the few organisms on the planet who create structures that can be seen from space (Figure 1).

Figure 1: Australia’s Great Barrier Reef as seen from space by NASA’s Multi-angle Imaging SpectroRadiometer (MISR) instrument. Photo: NASA Earth Observatory.

Many coral species on reefs around the globe are also a part of a very special partnership with a single- celled photosynthetic marine alga in the genus Symbiodinium. Colloquially referred to as zooxanthellae, the symbiodinium live within the thin layer of tissue on the outside of coral skeletons, giving them the colors that we see on healthy coral reefs (Figure 2).

Generally speaking, any relationship where organisms live in close relation with each other is called a symbiosis. But, whether this relationship is positive, negative, or neutral for each organism involved can vary. The symbiosis between corals and zooxanthellae is supposed to be mutualistic, meaning that they both receive positive benefits from their partnership. Zooxanthellae are provided with a safe place to live within the coral tissue, and they also get to use the coral’s waste products as nutrients to power photosynthesis. The corals, in turn, receive energy in the form of sugars as products of the zooxanthellae’s photosynthesis, providing close to 90% of their energy.


Figure 2: A coral with individual polyps visible (left) and a close-up of two translucent coral polyps with zooxanthellae (the patches of brown; right). Photos: Coral Reef Alliance and Smithsonian Institution.

Like a good business deal, the two partners do better together than they would alone. The symbiosis between corals and zooxanthellae has allowed for corals to grow so successfully in tropical waters that are otherwise very nutrient- and food-poor. Without this partnership, coral reefs would not be the prolific ecosystems we see and rely on today.

However, as is true for humans, stress can cause a strain on a relationship. This is no different for corals and zooxanthellae, whose main source of stress in the past few decades has been rising ocean temperatures resulting from human additions of carbon dioxide to the atmosphere. At temperatures just ~1°C above mean summer values, the stress becomes too much, and a breakup occurs. During this breakup, referred to as coral bleaching, the corals expel their symbiotic algae, leaving behind the white coral skeleton covered by the now colorless tissue layer (Figure 3). Though some corals are able to regain their zooxanthellae once favorable conditions return, most corals die soon after bleaching occurs as they cannot feed themselves sufficiently without the symbiosis.

Figure 3: A healthy coral (left) and bleached coral (right). Image: The Ocean Agency / XL Catlin Seaview Survey / Richard Vevers.

For coral researchers, one of the main issues we face in addressing the problem of coral bleaching is truly understanding the cause and mechanism of the bleaching itself. Some have hypothesized that bleaching occurs when the thermal tolerance of corals and zooxanthellae is exceeded, whereas others suggest that damage to the zooxanthellae’s photosynthetic system releases compounds that are toxic to the corals, leading to an  expelling the algae.

In an article published in Nature’s ISME Journal this year, Dr. David Baker of the University of Hong Kong and colleagues provide evidence to suggest that under warming conditions, zooxanthellae actually become parasitic to corals, leading to their expulsion. This imbalance in the relationship is compounded when the corals are exposed to high nutrient concentrations, mimicking those that occur as a result of runoff and pollution from land.

The team measured respiration and growth in colonies of the coral Orbicella faveolata and their zooxanthellae from Belize in nutrient-enriched aquariums at temperatures both below and above the bleaching threshold. By using a combination of chemical isotopes to trace the uptake of nutrients and carbon, they were able to determine the effects of these stressors on the balance of the symbiotic relationship.

They found that while the corals experienced higher energy demands under higher temperatures, the zooxanthellae actually performed better – without any energy cost. When this occurs, the benefits of the symbiosis with zooxanthellae were exceeded by the costs to corals, and the mutualistic relationship became effectively parasitic. In addition, nutrient addition proved to benefit the zooxanthellae only, enhancing their growth exclusively, without sharing their enhanced resources with their hosts.

The results of this study suggest that as sea surface temperatures continue to rise, in concert with increased nutrient loading, corals will become increasingly selfish, leading to widespread coral bleaching.

Reports of massive bleaching events worldwide have been featured on the front pages of popular media outlets increasingly over the last few years. The 2014-2017 Global Coral Bleaching event affected more reefs than any previous bleaching event, and may have been the most severe event on record. In the Hawaiian Islands, between 32 and 56% of all corals bleached, and in Australia’s Great Barrier Reef, bleaching of more than 60% of all corals led to announcements that the world’s largest reef had died.

While some reports took a turn for the dramatic, there is no question that coral bleaching is happening, and will continue to occur unless we as humans change our habits. The large loss of corals has dramatic consequences, not only for the ecosystem itself, but also for humans. In addition to facilitating healthy fisheries which feed billions of people worldwide, coral reefs also dissipate wave energy, protecting coastlines and preventing erosion, and contain chemicals important for many pharmaceuticals, among many other ecosystem services. Thus, the loss of corals from bleaching (in addition to other causes such as trawling, ocean acidification, disease, and sedimentation) will have significant ecological and economic effects.

If coral scientists can understand the mechanism by which coral bleaching occurs, then we can more effectively work to prevent it in the future, or at least remedy the relationship before mass coral mortality occurs.


Baker, D.M., Freeman, C.J., Wong, J.C., Fogel, M.L. and Knowlton, N., 2018. Climate change promotes parasitism in a coral symbiosis. The ISME journal, p.1.

Hoegh-Guldberg, O., 1999. Climate change, coral bleaching and the future of the world’s coral reefs. Marine and freshwater research, 50(8), pp.839-866.

Weis, V.M., 2008. Cellular mechanisms of Cnidarian bleaching: stress causes the collapse of symbiosis. Journal of Experimental Biology, 211(19), pp.3059-3066


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