Thursday, 23 March 2017

After Deepwater Horizon spill: Which animals weathered the disaster




Scientists construct a food web of heavily oiled marshes in Barataria Bay, Louisiana

Date: March 13, 2017
Source: Rutgers University

A new study from a Coastal Waters Consortium team of researchers led by Rutgers University postdoctoral researcher, Michael McCann, has found which birds, fish, insects and other animals affected by the Deepwater Horizon explosion should be given top priority for conservation, protection and research.

Until now scientists didn't know which kinds of animals were most affected and what impact their collective fates had on the food chain after the offshore oil rig Deepwater Horizon exploded in 2010 and dumped 4.9 million barrels of oil into Louisiana's salt marshes.

"There were lots of studies about who eats whom, and about what species are sensitive to oil," says Olaf Jensen, professor of marine and coastal sciences in the School of Environmental and Biological Sciences, and co-author of the study. "We put those together and asked, 'Who is both important in the food web and really sensitive to oil?'" These are the species most in need of protection because their loss can have ripple effects throughout the food chain, said Jensen.

The study, published this month in Frontiers in Ecology and the Environment, in which the team of scientists from Rutgers University, Louisiana State University, Louisiana Universities Marine Consortium, University of North Carolina, East Carolina University, and Stony Brook University constructed a marsh food web for Barataria Bay, Louisiana. The study found that killifish played a key role in the food web and fared relatively well in the wake of the spill.

The researchers determined that terns, gulls and wading birds, such as herons, were both sensitive to oil and so extensively connected to other animals as prey and predator that their loss would impact other species in the food chain. Some studies indicate that the mortality among terns and gulls in Barataria Bay was as high as 32 percent.

Virus lethal to amphibians is spreading across Portugal




Date: March 13, 2017
Source: Plataforma SINC

A new strain of ranavirus is currently causing mass mortality in several species of amphibian in the Serra da Estrela, the highest mountain range in continental Portugal. This infectious agent is hypervirulent and also affects fish and reptiles, which complicates the situation, according to a study boasting the collaboration of the National Museum of Natural Sciences in Madrid.

An emerging virus is affecting amphibian populations in Portugal, but this is not the first time amphibians have been a source of worry in the country. In 2009, hundreds of midwife toads (Alytes obstetricans) were found dead in Serra da Estrela Natural Park.

A research study published in the journal Scientific Reports raises a new alert on this genus of virus, which has also been discovered in Spain and elsewhere in Europe. As Jaime Bosch, a researcher at the National Museum of Natural Sciences and co-author of the study, explains: "Ranaviruses have been known about for a long time, although in recent years globalisation is setting off mass mortalities throughout the world, and new strains also keep appearing, probably from Asia."

The fact that these viruses also affect fish and reptiles complicates the situation enormously, firstly because they can spread easily and also because of their persistence in the environment, even after amphibians disappear.

"They have probably been infecting amphibian populations in Spain for several decades. In 1992 we discovered what turned out to be the first known case in our country, although at the time we didn't even know exactly which organism caused the problem," the scientist adds.

In autumn 2011, another curious episode of mortality arose in the Serra da Estrela, which not only affected midwife toads but also other species of amphibians in the park. The episode was in contrast to all mortality patterns previously associated with chytridiomycosis on the Iberian Peninsula and Europe.

When the sea ice melts, juvenile polar cod may go hungry




Biologists confirm how heavily the fish depend on ice algae

Date: March 15, 2017
Source: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

Polar cod fulfil a key role in the Arctic food web, as they are a major source of food for seals, whales and seabirds alike. But the polar cod themselves might soon be the hungry ones. Under the ice of the central Arctic, the juvenile fish are indirectly but heavily dependent on ice algae. As a result, retreating sea ice could have far-reaching impacts on the food web. Though researchers have long since suspected this relation existed, an international team of researchers led by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), have now successfully confirmed it.

Arctic sea ice offers a veritable nursery ground for polar cod: young fish between one and two years old live in cracks and crevices under the ice. They drift along with the ice, which is most likely how they make their way from their spawning grounds in the waters of northern Siberia to the central Arctic. During their journey, the young polar cod feed on amphipod crustaceans, which in turn feed on ice algae. As such, there is a direct relation between the polar cod and the ice algae, which could ultimately threaten the young polar cod's survival. This was the key outcome of a study recently published in the journal "Progress in Oceanography." Amongst others, the research institute Wageningen Marine Research in the Netherlands joined in the study.

"Generally speaking, our findings indicate that polar cod are heavily dependent on ice algae," says first author and AWI biologist Doreen Kohlbach. "That means the rapid retreat of Arctic sea ice poses an especially serious threat for polar cod. When the ice retreats, it takes with it the basis of their diet. Given the polar cod's pivotal role, this could also produce changes throughout the entire food web."


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