[Video] Underwater robots help scientists see where marine larvae go and how they get there

ABy Thomas Wolcott, North Carolina State University; Donna Wolcott, North Carolina State University; John L. Largier, University of California, Davis, and Steven G. Morgan, University of California, Davis.

Many people who love the oceans never realize that a single drop of seawater is teeming with plankton, which means “drifters” in Greek. These organisms, which typically range in size from a pinhead down to the tip of a pin, spend their lives drifting with currents and form the base of ocean food chains.

Most larger marine organisms, from corals to crabs to fish, also begin life as tiny drifters. Females release eggs, or larvae, which join plankton and spend days to weeks adrift. Only larvae that arrive at the right habitats, at the right stage in their life cycles, will grow into a new generation. The rest will perish.

Scientists have long assumed that larvae are at the mercy of ocean currents. We cannot track such tiny creatures for weeks and months as ocean currents carry them over long distances, but many of us have wondered where they go and how they get there.

Seven crab larvae in a drop of water.
Peter Parks

Thousands of miles and decades apart, members of our team independently wrestled with this puzzle. Studying land crabs on Bermuda, Tom and Donna Wolcott of North Carolina State University wondered why larvae of one species seemed to return to the islands every year from the surrounding ocean, but those of another species did not. On the California coast, Steven Morgan at the University of California at Davis documented larval behaviors of shore-dwelling species that apparently enabled them to avoid being swept offshore by strong currents. And Morgan’s colleague John Largier explored the pattern of currents in which the larvae drifted.

We needed a new tool to address these issues. The Wolcotts reasoned that they could not put transmitters on individual larvae, but they could design something that behaved like a larva. If it could be tracked, following a group of them would reveal the path of a cloud of larvae.

Over three decades they developed a robot “larval mimic” that senses its environment, mimics the vertical swimming responses of larvae and relays its location. Following a cluster of these robots would show where larvae would be carried by currents, depending on the depths the larvae chose.

This research is providing insights into how evolution has “tuned” subtle changes in larval swimming behaviors to maximize the chances that larvae drifting in the ocean will beat the enormous odds against them and arrive at suitable habitat for settlement.

Following the currents – or not

The strong and persistent currents off the northern California coast provide an excellent opportunity to test the effectiveness of larval behaviors. Upwelling occurs along coastlines that run north-south along the western margins of continents, where prevailing winds combine with the rotation of the Earth to drive surface waters away from shore. This process draws deep, cold, nutrient-rich waters to the surface, supporting some of the most productive fishing grounds in the world.

Upwelling brings cold, nutrient-rich water to the surface along coastlines.

Scientists have long assumed that during upwelling, larvae developing near the surface were carried away from shore and lost at sea. But when Morgan and colleagues towed plankton nets at discrete depths throughout the water column and across the continental shelf of northern California, they found that larvae of most species remained within three kilometers of the shore where they originated.

How do such tiny organisms control their positions in the water? It has been known for decades that even though larvae cannot swim against currents, they can swim vertically from one layer of water to another moving in a different direction. The evolution of vertical swimming behaviors could help larvae to reliably stay close to shore, or to range different distances across the continental shelf.

By regulating their depth, larvae appear to have a surprising amount of control over how far from home they are transported. Many marine populations need this ability for successful reproduction. It also determines which populations exchange larvae sufficiently to remain a single genetically similar population along the coastline.

Knowing that larvae can regulate their movements in this way could affect how we design and evaluate networks of marine protected areas to conserve ecosystems and populations of economically and ecologically important species. It also is relevant for tracking the spread of invasive species, and for analyzing how marine species adapt to a warming planet by shifting their ranges north or south along the coast.

A robot that mimics larvae

Tom and Donna Wolcott named their robot the Autonomous Behaving Lagrangian Explorer, or ABLE – autonomous because it is deployed without a tether, and Lagrangian because it is carried along with the water parcel in which it is embedded. The Lagrangian approach to studying currents consists of following the movement of a parcel of water, typically with some sort of “drifter” – in this case, a drifting robot.

But the ABLE is not entirely passive: It mimics larval behavior by monitoring time and conditions around it, including depth, temperature, light, salinity and vertical water motion every 10 seconds. Then it calculates a new “target depth” appropriate for that larva and swims toward it by subtly adjusting its buoyancy. It can log up to 16 megabytes of environmental data from its sensors and upload them after the “bot” is recovered from the water.

Testing ABLE at sea and in a swimming pool.

When the Wolcotts snorkeled with several of the initial ABLEs in the Bahamas in 1994, they could see them swimming up and down as programmed. The ABLEs could also be tracked by following signals from their ultrasonic pingers – until drowned out by the din of snapping shrimp.

Next the Wolcotts created ABLEs to simulate mobile phytoplankton for research by North Carolina State University marine scientist Dan Kamykowsky on transport of “red tides,” which are dense blooms of toxic algae. The Wolcotts added a light sensor so that ABLE could calculate photosynthesis and respiration. The ABLEs could then mimic the movements of the algal cells, moving upward to meet their needs for light and photosynthesis and deeper to find essential nutrients.

These ABLEs also carried redundant tracking hardware: GPS receivers to get position fixes, VHF radio beacons to transmit those positions and LED beacons so that researchers could retrieve them from the water after dark. Bluetooth wireless connectivity enabled the bots to talk to computers while their pressure housings were sealed. This version successfully emulated red tide algae during experiments in the Gulf of Mexico.

The newest ABLEs carry a transmitter to relay the latest GPS fixes via satellites to our computers and smartphones, and a sensor to keep the robots from getting stuck on the sea bottom. Running all of this gear and simulating larval swimming behaviors requires a program that contains roughly 3,000 lines of code.

Cracking the black box

Steven Morgan first saw the Wolcotts demonstrate an ABLE prototype in a hotel pool at a 1996 conference. In 2015, after two more decades of “ABLE evolution” and field testing, we conducted the first experiments using them to understand how larvae were transported in currents near the University of California at Davis’s Bodega Marine Laboratory in northern California.

ABLEs deployed in northern Bodega Bay.
Grant Susner

Circulation is more complex around headlands and bays than along straight coastlines, which makes it especially hard to predict where larvae go. Based on prior study of larval behavior and currents, Morgan and Largier predicted that during upwelling, larvae in surface waters would be transported far to the south, while larvae in bottom waters would stay put. They also expected larvae that remain in bottom waters during the day, rising to the surface to forage at night after winds subside, would stay put.

To test this hypothesis, we repeatedly released ABLEs programmed to simulate larvae with different vertical swimming behaviors and tracked them for 24 hours. Their movements demonstrated that larvae that remained near the surface would be transported up to 8 kilometers southward within 24 hours. In strong contrast, ABLEs that stayed deep in the water column remained near where they were released. ABLEs that migrated to the surface at night did not travel much farther than the ones that remained deep, moving less than 2 kilometers.

Results of a typical 24-hour deployment of nine ABLEs: three remaining near the surface (blue), three near the bottom (green) and three undertaking a DVM (pink).
Steven Morgan, University of California, Davis, Author provided

From these experiments, it is evident that vertical positioning in currents, even if cued only by the clock, has profound effects on larval movements. ABLE’s ability to respond to environmental cues, and its battery life of over two weeks, also will enable us to examine how changes in depth preferences affect transport of larvae during the course of development.

Larvae of many species occur near the surface in offshore-flowing currents early in their development and are carried away from shore. Older larvae descend into deep shoreward-flowing currents and return onshore to habitats in which they can metamorphose and become adults. In effect, they use currents like conveyor belts to travel out and back across the continental shelf.

Now we are deploying ABLEs with different behaviors to collect the first experimental evidence of how patterns of vertical migration by larvae determine how far offshore and alongshore they travel. This information will help us crack the “black box” and reveal where larvae of different species go.

We also plan to deploy ABLEs in different environments, such as estuaries. Eventually we plan to return to Bermuda or another isolated island to answer the Wolcotts’ original question: How do larvae find their way back to the shores of a speck in the middle of a vast ocean?

The ConversationThomas Wolcott, Professor Emeritus of Marine, Earth and Atmospheric Sciences, North Carolina State University; Donna Wolcott, Associate Professor Emerita of Marine, Earth and Atmospheric Sciences, North Carolina State University; John L. Largier, Professor of Coastal Oceanography, University of California, Davis, and Steven G. Morgan, Professor of Environmental Science and Policy, University of California, Davis

This article was originally published on The Conversation. Read the original article.

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As climate change alters the oceans, what will happen to Dungeness crabs?

By Paul McElhany, National Oceanic and Atmospheric Administration.

Many travelers visit the Pacific Northwest to eat the region’s famous seafood – particularly Dungeness crabs, which are popular in crab cakes or wrestled straight out of the shell. Locals also love catching and eating the feisty creatures. One of my favorite ways to spend an afternoon is fishing for Dungeness crabs from a pier in Puget Sound with my daughter. We both enjoy the anticipation of not knowing what we will discover when we pull up the trap. For us, the mystery is part of the fun.

But for commercial crabbers who bring in one of the most valuable marine harvests on the U.S. West Coast, that uncertainty affects their economic future.

In my day job as a research ecologist with the National Oceanic and Atmospheric Administration’s Northwest Fisheries Science Center, I study how changes in seawater’s acidity from absorbing carbon dioxide in the air, referred to as ocean acidification, may affect the success of recreational crabbers like me and the fortunes of the crabbing industry.

Contrary to early assumptions that acidification was unlikely to have significant effects on Dungeness crabs, we found in a recent study that the larvae of this species have lower survival when they are reared in the acidified ocean conditions that we expect to see in the near future. Our findings have sobering implications for the long-term future of this US$170 million fishery.

Pike Place Market, Seattle.
jpellgen/Flickr, CC BY-NC-ND

Dissolving shells

Ocean acidification is a global phenomenon that occurs when we burn fossil fuels, pumping carbon dioxide (CO2) into the atmosphere. Some of that CO2 is absorbed by the ocean, causing chemical changes that make ocean water more acidic, which can affect many types of marine life. The acidification taking place now is the most rapid change in ocean chemistry in at least 50 million years.

Many organisms, including numerous species of fish, phytoplankton and jellyfish, do not seem to be greatly affected by these changes. But some species – particularly oysters, corals and other organisms that make hard shells from calcium carbonate in seawater – die at a higher rate as the water in which they are reared becomes more acidic. Acidification reduces the amount of carbonate in the seawater, so these species have to use more energy to produce shells.

If water becomes extremely acidic, their shells can literally dissolve. We have seen this happen in experiments using small free-swimming marine snails called pteropods.

Dungeness crabs make their exoskeleton primarily from chitin, a modified polysaccharide similar to cellulose, that contains only small amounts of calcium carbonate. Initially, scientists predicted that the species would experience relatively limited harm from acidification. However, recent experiments in our lab led by graduate student Jason Miller suggest that Dungeness crabs are also vulnerable.

Crab fishing boats, Half Moon Bay, California.
Steve McFarland/Flickr, CC BY-NC

Fewer crabs, growing more slowly

In these experiments we simulated CO2 conditions that have been observed in today’s ocean and conditions we expect to see in the future as result of continued CO2 emissions. By raising Dungeness crab larvae in this “ocean time machine,” we were able to observe how rising acidification affected their development.

Dungeness crabs’ life cycle starts in autumn, when female crabs each produce up to two million orange eggs, which they attach to their abdomens. The brooding females spend the winter buried up to their eye stalks in sediment on the sea floor with their egg masses tucked safely under a flap of exoskeleton.

In spring the eggs hatch, producing larvae in what is called the zoea stage – about the size of a period in 12-point type. Zoea-stage crab larvae look nothing like adult crabs, and have a completely different lifestyle. Instead of lurking on the bottom and scavenging on shrimp, mussels, small crabs, clams and worms, they drift and swim in the water column eating smaller free-swimming zooplankton.

Dungeness crab larva, zoea stage. Oregon Department of Fish and Wildlife

After molting through five different zoea stages, which all look pretty similar, the larvae reach the megalopae stage when they are about two months old. Next they molt into the benthic juvenile stage, which looks a lot like an adult crab, and settle to the sea floor. The crabs finally reach adulthood about two years after hatching.

Some common pH values. Wikipedia, CC BY

In our experiment, divers collected brooding female Dungeness crabs from the bottom of Puget Sound in Washington state. We reared larvae produced from these females in three different CO2 levels that roughly corresponded to acidification levels now (pH 8.0), levels projected to be relatively common at midcentury (pH 7.5) and levels expected in some locations by the end of the century (pH 7.1). The pH scale measures how acidic or basic (alkaline) a substance is, with lower pH indicating a more acidic condition and a decrease of one unit (i.e., from 8 to 7) representing a tenfold increase in acidity. This means that the ocean today (average pH 8.1) is about 25 percent more acidic than the ocean in pre-industrial times (pH 8.2) and the ocean of the future is expected to be about 100 percent more acidic than today.

Describing exactly how acidic Puget Sound is now or could be in the future is complicated, because CO2 levels in different parts of the Sound vary widely and there are seasonal shifts. Generally, however, Puget Sound is naturally more acidic than other parts of the ocean because currents bring acidic waters from the deep ocean to the surface there. But shellfishermen are concerned because human-produced CO2 is causing large changes on top of these background levels of variation.

We found that although eggs reared in high-CO2 water hatched at the same rate as those in lower-CO2 water, fewer than half as many of the larvae reared in highly acidic conditions survived for more than 45 days compared to those raised under current conditions (Figure 2). Put another way, the mortality rate in acidified conditions was more than twice as high as in more contemporary CO2 conditions. Crabs raised in more acidic water also developed more slowly, and fewer of them reached the 4th zoeal stage compared to larvae raised in less-acidic water. This slower development rate probably reflected the extra energy that larvae had to expend to grow in a more acidic environment.

Su Kim/NOAA Fisheries, Author provided

We are not entirely sure what these results mean for future populations of Dungeness crabs, but there is reason for concern. Significantly lower larval survival may translate into fewer adult crabs, which will have ripple effects on the fishery and Pacific coastal food webs.

Slower larval growth could lead to a mismatch in the timing of predators and prey. Crab larvae depend on finding abundant prey during certain times of the year, and organisms such as Chinook salmon and herring that prey on crab larvae depend on an abundance of crabs at particular times of the year. Any factor that disrupts the timing of development can have important ecological consequences.

Dungeness crab are found along the Pacific coast from California to Alaska, and over that range they experience wide variations in water temperature, ecological communities and pH. It is possible that individual crabs may be able to tolerate new CO2 conditions during their lives – in other words, to acclimate to the changes. Or if some crabs are just better able to tolerate high-CO2 conditions more easily than others, they may pass on that ability to their offspring, allowing the species to adapt to rising acidification through evolution. Our next studies will examine how Dungeness crabs may acclimate or adapt to increasing acidification.

Today Dungeness crab populations are generally in good condition, and my daughter and I usually come home from our crabbing adventures victorious. It is hard to imagine that this abundant species is at risk in the coming decades, but we need to anticipate how it could be affected by acidification. For Dungeness crabs and many other species, it is essential to understand how human actions today could alter sea life in tomorrow’s oceans.

Jason Miller, a former biologist at NOAA’s Northwest Fisheries Science Center and graduate student at the University of Washington, was lead author of the Dungeness crab larval exposure study on which much of this article is based.

The ConversationPaul McElhany, Research Ecologist, National Oceanic and Atmospheric Administration

This article was originally published on The Conversation. Read the original article.

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There are bright spots among the world’s coral reefs – the challenge is to learn from them

By Joshua Cinner, James Cook University.

Despite substantial conservation efforts, human impacts are harming coral reefs all over the world. That in turn affects the millions of people who depend on reefs for their livelihoods. It’s a gloomy picture, but there are some bright spots.

In a study that appears on the cover of this week’s Nature, I and 38 international colleagues identify 15 places around the world where the outlook is not so bleak. Many of them are in surprising places like Pacific island states, which may not have lots of money for conservation but do have a close social connection to the health of their oceans.

Unlike scientific studies that look at averages or trends, we took a slightly different approach and focused on the outliers – the places bucking the trend. This type of “bright spot” approach has been used in a range of fields, including business, health and human development, to search for hope against backgrounds of widespread failure.

One example is in Vietnam, where the charity Save the Children looked at poor children who bucked the trend of widespread malnutrition. They discovered that poor families with healthier kids were collecting small crabs and shrimp from their rice paddies and grinding them into their kids’ food, and feeding them smaller, more frequent meals. These practices have now spread to more than 2.2 million families, cutting childhood malnutrition by 65%.

This is a great example of local habits that, once identified and spread more widely, have had a hugely beneficial impact. My colleagues and I wanted to see if we could do the same for the world’s coral reefs.

Searching for bright spots

We carried out more than 6,500 reef surveys across 46 countries, states and territories around the world and looked for places where reef fisheries should have been degraded, but weren’t.

We defined these bright spots as reefs with more fish than expected, based on their exposure to pressures like human population, poverty and unfavourable environmental conditions. To be clear, bright spots are not necessarily “pristine” reefs, but rather reefs that are doing better than they should be given the circumstances. They are reefs that are “punching above their weight”.

We identified 15 bright spots and 35 dark spots (places that were doing much worse than expected) in our global survey. The bright spots were mainly in the Pacific Ocean, and two-thirds of them were in populated places like the Solomon Islands, parts of Indonesia, Papua New Guinea and Kiribati.

Dark spots were more globally distributed; we found them in every major ocean, sometimes in places that are generally considered to be pristine, such as in the northwestern Hawaiian islands. Again, this doesn’t mean the reefs were necessarily in terrible shape – just worse than we would expect, given that in cases such as Hawaii they are remote, well protected and in a wealthy country with a strong capacity to govern their reefs.

The Great Barrier Reef, which is often considered the best-managed reef in the world, performed largely as we would expect it to, given that it is in a wealthy country with low population density, and many of its individual reefs are offshore and mostly remote from people.

Look after your fish, and they will look after you.
Tane Sinclair-Taylor, Author provided

What makes bright spots special?

We wanted to learn what these bright spots were doing differently. Why were they able to withstand pressures that caused other reef systems to suffer? And could lessons from these places inform reef conservation in other areas?

Our preliminary investigation showed that bright spots (and their nearby human communities) generally had four crucial characteristics:

  • strong local sea traditions, which include ownership rights and/or customary practices such as periodically closing a reef to fishing
  • high levels of participation in management by local people
  • high levels of dependence on fishing (this seems counter-intuitive, but research shows that where people’s livelihoods depend on a resource, they are more committed to managing it responsibly)
  • deep-water refuges for fish and corals.

Importantly, the first two are malleable (for instance, governments can invite local people to become more involved with reef management), whereas the latter two are less so (it is hard to change people’s livelihoods, and impossible to change the undersea landscape in a way that wouldn’t devastate reefs in the process).

We also found some common characteristics of dark spots

  • use of particular types of fishing nets that can damage habitat
  • widespread access to freezers, allowing fish catches to be stockpiled
  • a recent history (within the past five years) of environmental disturbance such as coral bleaching or cyclone.

Where next?

We believe that the bright spots offer some hope and some solutions that can be applied more broadly across the world’s coral reefs.

Specifically, investments that foster local involvement and provide people with ownership rights to their marine resources can help people develop creative solutions and defy expectations that reefs will just continue to get more degraded.

Conversely, dark spots can highlight the development or management pathways to avoid. In particular, it is important to avoid investing in technology that allows for more intensive fishing, particularly in places with weak governance or where there have already been environmental shocks like cyclones or bleaching.

The next step is to dig deeper into the social, institutional and ecological dynamics in the bright spots. By looking to the places that are getting it right – whether by accident or design – we can hopefully make the future a bit brighter for reefs the world over.

The ConversationJoshua Cinner, Senior Research Fellow, ARC Centre of Excellence, Coral Reef Studies, James Cook University

This article was originally published on The Conversation. Read the original article.

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These Coral Reefs Have Become ‘Ghost Towns’ in Just a Few Months [Video]

A team of marine scientists has returned from nearly a month of scuba diving on coral reefs in the middle of the equatorial Pacific Ocean. What they saw will haunt them for a long time.

“It’s as if someone has thrown a fuzzy red/brown blanket over the reef, turning it all one color,” says Kim Cobb, a professor in Georgia Tech’s School of Earth and Atmospheric Sciences. “Right now it looks okay from afar, with all the coral structure still in place. But when you get up close, you see that it’s all dead, as far as the eye can see. It’s very eerie.”


Cobb and colleagues worked with biologist Julia Baum and her team of University of Victoria researchers on Kiritimati Island (also known as Christmas Island), the world’s largest coral atoll. Christmas Island is about 150 miles north of the equator and 1,340 miles south of Hawaii. The current El Niño is the strongest ever recorded, and it has hit this area harder than anywhere else on the planet.

When the Georgia Tech team visited the reefs last November, 50 to 90 percent of corals they saw were bleached and as many as 30 percent were already dead. This time, after months of warm waters powered by the El Niño, the numbers were starker. After extensive underwater surveys around the atoll, Baum’s team estimates that 80 percent of the corals are dead and 15 percent are bleached. Only 5 percent are still alive and healthy.

“To see the reefs change this dramatically in just a few months is shocking,” says Baum. “We were bracing ourselves for the worst, but seeing it with our own eyes was surreal. Christmas Island’s coral reefs are like ghost towns now. The structures are all still there, but no one is home.”


Corals are communities of animals that have tiny photosynthetic algae living inside them in a mutually beneficial relationship. The algae provide corals with their vibrant corals, along with a vital source of food via photosynthesis. Corals, in turn, provide the structure that shelters their tiny algal symbionts.

Corals are very temperature-sensitive. A rise of just 1-1.5 degrees Celsius can stress coral enough to evict the algae until the heat stress subsides. This leaves a ghostly white coral skeleton and is known as “bleaching.” During protracted warm water events, such as the current El Niño, bleached corals aren’t able to bring their symbiotic plants back in, and they can die of starvation.

Temperatures on Christmas Island have been between 1.5 to 3 degrees Celsius higher than normal for the past 10 months straight. “This intense heat stress has transformed some of the world’s healthiest coral reefs into graveyards,” says Baum. “To our knowledge, this is the greatest coral mass mortality event at a single location on record.”


Many other areas in the world’s oceans are also showing extensive bleaching this year, including Australia’s Great Barrier Reef, but the Christmas Island corals were pushed far beyond bleaching.

Cobb and Baum think it may take a decade or more for the Christmas Island reefs to recover, but they might never look the same because of warmer-than-average temperatures and lower ocean acidity. Both are the consequences of rising greenhouse gases.

“Aside from their sheer beauty and appeal, coral reefs provide a host of ecosystem services that are critical to a healthy ocean,” says Cobb. “When remote reefs like Christmas Island succumb to acute temperature stress, it’s a wake-up call for the rest of the world’s reefs, which will come under increasing stress from climate change.”

“Christmas Island’s people rely on the reefs for their food and their livelihoods, so they’ll be profoundly affected by this event,” says Baum. She and her team will be studying the reefs carefully over the coming years to assess the recovery and learn more about how some corals are managing to resist heat damage. At the same time, Cobb and her students will work to determine whether the record-breaking 2015/2016 El Niño event is a portent of future El Niño events under continued climate change.

“Our research will provide important new insights into how corals may be able to survive more frequent temperature extremes over the next century,” says Baum. “In the meantime, this event is a vivid reminder that the effects of climate change are happening now, and that the choices we make about greenhouse gas emissions in the next decades will have long-term effects.”

Source: Republished from Futurity.org as a derivative work under the Attribution 4.0 International license. Original article posted to Futurity by .

Featured Photo Credit: Georgia Tech

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Is global warming causing marine diseases to spread?

Charlotte Eve Davies, Universidad Nacional Autónoma de México (UNAM)

Global climate change is altering the world’s oceans in many ways. Some impacts have received wide coverage, such as shrinking Arctic sea ice, rising sea levels and ocean warming. However, as the oceans warm, marine scientists are observing other forms of damage.

My research focuses on diseases in marine ecosystems. Humans, animals and plants are all susceptible to diseases caused by bacteria, viruses, parasites and fungi. Marine diseases, however, are an emerging field.

Infectious agents have the potential to alter ocean life in many ways. Some threaten our food security by attacking important commercial species, such as salmon. Others, such as bacteria in oysters, may directly harm human health. Still others damage valuable marine ecosystems – most notably coral reefs.

To anticipate these potential problems, we need a better understanding of marine diseases and how climate change affects their emergence and spread.

Warming waters promote marine diseases

Recent studies show that for some marine species diseases are spreading and increasing. Climate change may also promote the spread of infectious agents in oceans. Notably, warming water temperatures can expand these agents’ ranges and introduce diseases to areas where they were previously unknown.

Many diseases of marine species are secondary opportunist infections that take advantage when a host organism is stressed by other conditions, such as changes in pH, salinity or temperature. A bacterium that is dormant (and therefore noninfective) at a certain temperature may thrive at a slightly higher temperature.

One well-documented example is the emergence of epizootic shell disease (ESD) in American lobsters. This disease, thought to be caused by bacteria, is characterized by lesions that penetrate inward from a lobster’s shell surface towards the inner flesh, making infected lobsters unmarketable. ESD can also kill lobsters by making it difficult for them to shed their shells in order to grow.

An American lobster with epizootic shell disease (ESD). para_sight/flickr

In the 1990s, following almost a decade of above-normal summer temperatures, ESD affected so many lobsters that the Atlantic States Marine Fisheries Commission declared that the Southern New England fishery (Connecticut, Massachusetts, New York and Rhode Island) was in collapse and recommended closing it.
Fishery models that incorporated shell disease offered convincing evidence that ESD was a major factor in the decline of the stock. This episode underscores the importance of considering marine diseases in stock assessments and fishery management.

Now there are concerns that ESD will continue to spread north to Maine’s US$465.9 million lobster fishery. In 2015 the Gulf of Maine showed record high abundances of lobster, making it one of the most productive fisheries in the world.

However, sea surface temperatures in the Gulf of Maine have increased faster than 99 percent of the global ocean over the past decade, warming three times faster than the global average. Since temperature is a primary factor in the spread of this disease, observers fear that it could have devastating effects on Maine’s lobster fishery.

There is also a risk that ESD could spread from American lobsters to other fisheries. Seafood wholesalers have imported live American lobsters into Europe for decades, which can result in their escape into the wild. Last summer the United Kingdom’s Marine Management Organization warned U.K. fishermen that because the European lobster shares similar habitats, food sources and diseases with the American lobster, ESD could spread between the species.

As a doctoral student at Swansea University, U.K., I collaborated with the New England Aquarium in Boston, Massachusetts to investigate this possibility. While we found that European lobsters were more likely to develop shell disease when reared in the presence of American lobsters, on the positive side, they don’t seem to get the same shell disease as American lobsters.

This means that European lobsters may be better equipped to deal with outbreaks of ESD. But with sea surface temperatures in U.K. coastal waters rising since the 1980s by around 0.2-0.9 degrees Celsius per decade, it is important to monitor U.K. waters for this disease.

European lobsters with mild, none and severe shell disease. Andrew Rowley/Swansea University

Tropical disease

Now I am now studying the Panuliris argus_1 virus (PaV1) in the Caribbean spiny lobster, where the picture is more dire. Discovered around 2000, this virus is present from the Florida Keys to Venezuela. It can infect up to 60 percent of lobsters in some areas. Laboratory studies indicate that lobsters held in high-temperature seawater and exposed to PaV1 develop active and more intense infections much more quickly than those held at lower temperatures.

Studies from 1982 to 2012 show that waters in the Caribbean are warming, with the most significant temperature increase occurring over the past 15 years – approximately the period when PaV1 appeared. If PaV1 continues to spread, it could have significant effects on the health of Caribbean reefs as a whole, as well as on the valuable Caribbean lobster fishery.

Monitoring more diseases

Many other species are also showing increasing effects from marine diseases. The frequency of coral diseases has increased significantly over the last 10 years, causing widespread mortality among reef-building coral, which are home to more than 25 percent of all marine fish species.

In the Pacific, more than 20 species of sea stars were devastated by a wasting disease that ranged from Mexico all the way up to Alaska in 2013 and 2014. Research suggests that 90 percent of some populations were wiped out, and some adult populations have been reduced to a quarter of pre-outbreak numbers.

Scientists believe the cause is a virus which becomes more active in warmer conditions. In both field surveys and laboratory experiments, starfish were found to react faster to the disease in warmer water than in cooler temperatures.

Starfish on the shore at Umpqua Lighthouse State Park – Winchester Bay, Oregon. skipplitt/flickr

As the oceans continue to warm, it is crucial to understand how our actions are affecting marine life. Some species will not be able to withstand the increase in temperature. The most recent U.S. National Climate Change Assessment projects that outbreaks of marine diseases are likely to increase in frequency and severity as waters warm under climate change. Researchers are working around the world to determine whether and how species will survive disease events in our increasingly altered oceans.

The ConversationCharlotte Eve Davies, Postdoctoral Researcher at the Institute of Marine Sciences and Limnology, Universidad Nacional Autónoma de México (UNAM)

This article was originally published on The Conversation. Read the original article.

Featured Photo Credit: James St. John/Flickr, CC BY

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Solving ‘Darwin’s Paradox’: why coral island hotspots exist in an oceanic desert

Andrew Frederick Johnson, University of California, San Diego

It was Charles Darwin, almost 200 years ago, who first asked how it could be that coral reefs could flourish in relatively barren parts of the Pacific Ocean. This conundrum subsequently became known as Darwin’s Paradox.

A study published this week in Nature Communications helps answer just how coral oases can exist in oceanic deserts.

The simple explanation is the presence of microscopic aquatic plants known as phytoplankton. The more complicated, scientific answer – that asks why coral islands are such productive hotspots – is known as the Island Mass Effect (IME).

The findings of the new study provide scientists who study marine fisheries and habitats with important insights into how coral reef island systems can be so productive, acting as hotspots of species diversity which, in turn, help populate fisheries and provide coastal protection. This knowledge can help inform ocean management plans, particularly as ecosystems respond to climate change.

Illustration of the Island Mass Effect from the new study published in Nature.

The Island Mass Effect (IME)

The IME, first described by the University of Hawaii botanist Maxwell S. Doty and colleagues, is a phenomenon in which the growth of phytoplankton is enhanced close to island-reef ecosystems.

Until now, all studies trying to explain the reasons for the IME have been done over small, geographically confined areas, such as a single island or coral reef group.

This is where the Nature Communications paper’s lead author, Jamison Gove of the National Oceanic and Atmospheric Administration (NOAA), and his colleagues come in.


Hagfish ‘Slime Clouds’ Have Scientists Stumped

The hagfish has a bizarre way of fending off predators: It secretes a slime mass that can immobilize vast amounts of water. Any fish that attempts to attack the hagfish will likely suffocate on the slime.

This creature and its slime caught the attention of Simon Kuster, a researcher at ETH Zurich, after he saw a BBC documentary about the Atlantic hagfish (Myxine glutinosa).


“As a chemist and material scientist, I couldn’t help but wonder what this slime consists of and what factors allow to immobilize such enormous amounts of water,” says Kuster.

Kuster is supervising an effort to figure out how hagfish form the slime, its structure, and how to recreate it.

Continue reading to learn what the researchers have discovered so far.


Far more microplastics floating in oceans than thought

Kara Lavender Law, Sea Education Association and Erik van Sebille, Imperial College London

Plastic pollution in the ocean frequently appears as seabird guts filled with cigarette lighters and bottle caps, marine mammals entangled in fishing gear and drifting plastic bags mimicking a gelatinous meal. Last year, a study estimated that around eight million metric tons of our plastic waste enter the oceans from land each year.

But where this plastic ends up and what form it takes is a mystery. Most of our waste consists of everyday items such as bottles, wrappers, straws or bags. Yet the vast majority of debris found floating far offshore is much smaller: it’s broken-down fragments smaller than your pinky fingernail, termed microplastic.

In a newly published study, we showed that this floating microplastic accounts for only about 1% of the plastic waste entering the ocean from land in a single year. To get this number – estimated to be between 93,000 and 236,000 metric tons – we used all available measurements of floating microplastic together with three different numerical ocean circulation models.

Getting a bead on microplastics

Our new estimate of floating microplastic is up to 37 times higher than previous estimates. That’s equivalent to the mass of more than 1,300 blue whales.

The increased estimate is due in part to the larger data set – we assembled more than 11,000 measurements of microplastics collected in plankton nets since the 1970s. In addition, the data were standardized to account for differences in sampling conditions.

For example, it has been shown that trawls carried out during strong winds tend to capture fewer floating microplastics than during calm conditions. That’s because winds blowing on the sea surface create turbulence that pushes plastics down to tens of meters depth, out of reach of surface-trawling nets. Our statistical model takes such differences into account.

Maps of three model solutions for the amount of microplastics floating in the global ocean as particle counts (left column) and as mass (right column). Red colors indicate the highest concentrations, while blue colors are the lowest. van Sebille et al (2015)

The broad range in our estimates (93 to 236 thousand metric tons) stems from the fact that vast regions of the ocean have not yet been sampled for plastic debris.

It is widely understood that the largest concentrations of floating microplastics occur in subtropical ocean currents, or gyres, where surface currents converge in a kind of oceanographic “dead-end.”

These so-called “garbage patches” of microplastics have been well-documented with data in the North Atlantic and North Pacific oceans. Our analysis includes additional data in less sampled regions, providing the most comprehensive survey of the amount of microplastic debris to date.

However, very few surveys have ever been carried out in the Southern Hemisphere oceans and outside of the subtropical gyres. Small differences in the oceanographic models give vastly different estimates of microplastic abundance in these regions. Our work highlights where additional ocean surveys must be done in order to improve microplastics assessments.

And the rest?

Floating microplastics collected in plankton nets are the best-quantified type of plastic debris in the ocean, in part because they were initially noted by researchers collecting and studying plankton decades ago. Yet microplastics represent just part of the total amount of plastic now in the ocean.

After all, “plastics” is a collective term for a variety of synthetic polymers with variable material properties, including density. This means some common consumer plastics, such as PET (resin code #1, stamped on the bottom of clear plastic drink bottles, for example), are denser than seawater and will sink upon entering the ocean. However, measuring plastics on the seafloor is very challenging in shallow waters close to shore, let alone across vast ocean basins with an average depth of 3.5 kilometers.

It’s also unknown how much of the eight million metric tons of plastic waste entering the marine environment each year lies on beaches as discarded items or broken-down microplastics.

In a one-day cleanup of beaches around the world in 2014, International Coastal Cleanup volunteers collected more than 5,500 metric tons of trash, including more than two million cigarette butts and hundreds of thousands of food wrappers, drink bottles, bottle caps, drinking straws and plastic bags.

We do know that these larger pieces of plastics will eventually become microparticles. Still, the time it takes large objects – including consumer products, buoys and fishing gear, for example – to fragment to millimeter-sized pieces upon exposure to sunlight is essentially unknown.

Just how small those pieces become before (or if) they are degraded by marine microorganisms is even less certain, in large part because of the difficulty in collecting and identifying microscopic particles as plastics. Laboratory and field experiments exposing different plastics to environmental weathering will help unravel the fate of different plastics in the ocean.

Why it matters

If we know that a massive amount of plastic is entering the ocean each year, what does it matter if it is a bottle cap on a beach, a lost lobster trap on the seafloor, or a nearly invisible particle floating thousands of miles offshore? If plastic trash were simply an aesthetic problem, perhaps it wouldn’t.

Stellar sea lion with severe entanglement neck injury observed east of Vancouver Island in 2014. Wendy Szaniszio

But ocean plastics pose a threat to a wide variety of marine animals, and their risk is determined by the amount of debris an animal encounters, as well as the size and shape of the debris.

To a curious seal, an intact packing band, a loop of plastic used to secure cardboard boxes for shipping, drifting in the water is a serious entanglement hazard, whereas bits of floating microplastic might be ingested by large filter-feeding whales down to nearly microscopic zooplankton. Until we know where the millions of tons of plastics reside in the ocean, we can’t fully understand the full suite of its impacts on the marine ecosystem.

Yet we don’t have to wait for more research before working on solutions to this pollution problem. For the few hundred thousand tons of microplastic floating in the ocean, we know that it is not feasible to clean up these nearly microscopic particles distributed across thousands of kilometers of the sea surface. Instead, we have to turn off the tap and prevent this waste from entering the ocean in the first place.

In the short term, effective waste collection and waste management systems must be put in place where they are needed most, in developing nations such as China, Indonesia and the Philippines where fast economic growth accompanied by increased waste is outpacing the capacity of infrastructure to manage this waste. In the longer term, we must rethink how we use plastics with respect to function and desired lifetime of products. At the end of its life, discarded plastic should be considered a resource for capture and reuse, rather than simply a disposable convenience.

The Conversation

Kara Lavender Law, Research Professor of Oceanography, Sea Education Association and Erik van Sebille, Lecturer in Oceanography and Climate Change, Imperial College London

This article was originally published on The Conversation. Read the original article.

Featured Image Credit:  Giora Proskurowski/Sea Education Association, Author provided

Oceanic Researchers Find Deep Hydrothermal Vents Made of Something Completely Different

Normally, deep ocean hydrothermal vents are made of sulphide minerals, but in strange twist, oceanic researchers from the University of Southampton have found vents in the Caribbean that are unlike anything that has been discovered before. These vents are made of talc.

Researchers analyzed samples from active vents in the Von Damm Vent Field (VDVF), a vent field south of the Cayman Islands discovered by scientists and crew on board the RRS James Cook in 2010. Their findings appear in the journal Nature Communications.

“This vent site is home to a community of fauna similar to those found at the Mid-Atlantic Ridge in the Atlantic Ocean, but the minerals and chemistry at the Von Damm site are very different to any other known vents,” says Matthew Hodgkinson, a postgraduate research student at the National Oceanography Centre Southampton at the University of Southampton.

“The discovery of this new class of vent system serves to demonstrate our limited understanding of the ocean floor and the importance of and role for ‘discovery science’ in the oceans,” says Steve Roberts, professor of geology.

Hydrothermal vents form in areas where the Earth’s tectonic plates are spreading. At these sites, circulating seawater is heated by magma below the seafloor and becomes more acidic—leaching metals from the surrounding rocks and redepositing them as the hot water spews out of vents or ‘chimneys’ at the seabed and hits the cold seawater.

The Von Damm Vent Field system, however, is highly unusual compared to the typical hydrothermal vent that scientists are familiar with, besides the fact that they are made of talc. Continue to the next page to see what else has surprised the researchers about these vents…


Fish are Overwhelmed by Extra Algae

For years, scientists thought we had a secret weapon to protect coral reefs from nutrients flushed into the seas by human activity. Experiments suggested that herbivores such as fish, urchins, and sea turtles could keep corals and their ecosystems healthy by eating up extra algae that grew in the presence of these nutrients.

But a new study sheds doubt on that idea, underscoring the importance of sustainable growth in coastal areas.

“We found that while herbivores can control the effects of nutrient pollution in small-scale experiments, nutrient pollution at larger, realistic scales can overwhelm them,” says Mike Gil, a marine biologist who conducted the study as a doctoral student at the University of Florida. “We can’t just focus on protecting fish to keep coral reefs healthy. We have to take a more holistic approach.”

You don’t have to be a scuba diver to care about healthy reefs. In addition to sustaining sea turtles, whales, and dolphins, these ecosystems deliver a host of benefits to people, from providing medicinal compounds and seafood to protecting our coastlines from storm surges.

Nutrient enrichment can endanger these reefs: As our population grows, paving and development dump runoff laden with nitrogen and phosphorus into nearby bodies of water. Fertilizers intended for lawns and crops find their way into the seas, where sewer pipes might also be disgorging waste, especially in developing nations. The resulting enrichment can cause an overgrowth of algae that harms corals, sea grasses, and kelp.

In Akumal, Mexico, Gil has seen coral reefs decline and algae increase, even as the population of algae-eating fish remained stable and wondered if herbivores alone were really enough to defend the reefs.

The field experiments that gave rise to that idea typically looked at areas of nutrient pollution of a square meter or less, but nutrient pollution zones can cover hundreds of square kilometers. Researchers wanted to know if those results would scale up, but knew larger field experiments weren’t a viable option.

“It’s not ethical to nuke an entire system with nutrients,” Gil says—so he and coauthors fellow doctoral student Jing Jiao and Craig Osenberg, now at the University of Georgia—turned to mathematical modeling.

The findings, published in the journal Ecosystem Ecology, show that as an area affected by nutrient pollution increases, herbivores’ ability to control the resulting algae decreases, suggesting that these systems may be more vulnerable than previously thought. The results could guide policymakers in creating sustainable plans for industries such as tourism and fishing, which rely on healthy reefs, researchers say.

Tourists can help, too, Gil says, by opting for sustainable accommodations and tour operators when visiting sensitive areas such as the Yucatán, Hawaii, or the Great Barrier Reef.


Republished from Futurity.org  under the Attribution 4.0 International license with a new headline, featured image, and some additional article links removed. Original article posted on Futurity by  .

Featured Image Credit: Mike Gil/University of Florida