Yearly Archives: 2018

Salty Cinema V: Polar Oceans

Salty Cinema is back with short films and panel discussion on both the Arctic and Antarctic.

Thursday, December 13, 2019
Scripps Seaside Forum
5:30 – 7:30
Social Hour 7:30 – 8:30, please bring your own cup.
Event is free and open to the public.
Learn more about this event here

Fighting for the Ocean

How can we use the ocean without using it up? This is the primary question that Ayana Elizabeth Johnson is addressing through her work in the realm of ocean science and policy.

CMBC alumna Ayana Elizabeth Johnson. Photo: Erika Johnson/UC San Diego

Johnson is a woman of many talents: she’s a marine biologist, policy expert, conservation strategist, and graduate of Scripps Institution of Oceanography at UC San Diego (MS ’09, PhD ’11), where she studied marine biology through the Center for Marine Biodiversity and Conservation (CMBC). She’s also the founder and CEO of Ocean Collectiv, a strategy consulting firm for ocean sustainability grounded in social justice.

The impressive alumna and Triton 40 Under 40 recipient returned to campus on Sept. 26 to serve as keynote speaker at the Scripps Student Symposium (S3), an annual research conference organized by Scripps students. Now in its sixth year, the symposium features presentations and poster sessions designed to showcase the breadth of Scripps research to the new class of students.

Groupers on the Comeback in the Caymans

(From Reef Environmental Education Foundation eNews) REEF’s Grouper Moon Project, ongoing since 2001, was recently featured in Scientific American as a model for natural resource science. The project is a powerful collaboration between scientists at REEF, Cayman Islands Department of Environment, Scripps Institution of Oceanography, and Oregon State University, with input from Caymanian fishermen and support by local businesses. The work has connected cutting-edge science with the real-world need for understanding and protecting Nassau Grouper and their spawning aggregations. The full story, “Groupers on the Comeback in the Cayman Islands”, is available on the Scientific American Blog here.

Expedition to Unlock Secrets of Deep Dutch Caribbean

Explorer on the shore of uninhabited Klein Curaçao with R/V Chapman in the distance. Credit: Uncharted Blue

On August 27 a team of scientists and explorers will travel aboard the R/V Chapman to the uninhabited island of Klein Curaçao as part of a series of oceanographic expeditions designed to document the health and biodiversity of shallow and deep reef ecosystems. The expedition will explore the mesophotic zone — the furthest the sun can penetrate the ocean. “These areas are at the cutting edge of coral reef science as they are very poorly studied and are often made up of species of corals, fish and invertebrates that are totally new to science. It is becoming increasingly clear that mesophotic reefs are diverse and serve many critical ecosystem functions yet they are threatened by many of the same stressors as shallow coral reefs including coral bleaching, ocean acidification and sedimentation. It is essential that we better understand how deep mesophotic reefs function so that we can develop strategies to protect them before it is too late,” says Dr. David Kline, a lead scientist on the expedition and Research Biologist at UC San Diego’s Scripps Institution of Oceanography.

This will be the inaugural expedition in a series led by Uncharted Blue, a new organization, founded by CMBC Alumni.  Uncharted Blue connects adventure seekers with world renowned scientists and marine technology to fuel exploration of uncharted ocean destinations.

Read more:

Benthic Ecology Class Blogs

As an assignment for this year’s benthic ecology class,  Lisa Levin asked the students to create a science blog.  The topics cover changing coral reefs and their ecosystems services, climate change and the toxic relationship in corals, the loss of Mexico’s mangrove forests, jellyfish as a cuisine,  “marine vomit” and more.

These are now posted on the CMBC Blog: A View from the PIER.
We hope you find these entertaining and educational.


Congratulations to MAS-MBC students

Nineteen Master of Advanced Studies in Marine Biodiversity and Conservation successfully presented their capstone research at a the annual symposium earlier this week.

If you missed any part of the day long event, it has been recorded and is available here:

For a list of this year’s capstones and order of presentation, please visit:

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,


scripps oceanography uc san diego