#ecosystem stability

King crabs threaten Antarctic ecosystem due to warming ocean

Predators' arrival could radically alter marine life

King crabs may soon become high-level predators in Antarctic marine ecosystems where they haven't played a role in tens of millions of years, according to a new study led by Florida Institute of Technology.

"No Barrier to Emergence of Bathyal King Crabs on the Antarctic Shelf," published online in the Proceedings of the National Academy of Sciences, ties the reappearance of these crabs to global warming.

Lead author Richard Aronson, professor and head of Florida Tech's Department of Biological Sciences, said the rising temperature of the ocean west of the Antarctic Peninsula - one of the most rapidly warming places on the planet - should make it possible for king crab populations to move to the shallow continental shelf from their current deep-sea habitat within the next several decades.

Researchers found no barriers, such as salinity levels, types of sediments on the sea floor, or food resources, to prevent the predatory crustaceans from arriving if the water became warm enough.

That arrival would have a huge impact.

"Because other creatures on the continental shelf have evolved without shell-crushing predators, if the crabs moved in they could radically restructure the ecosystem," Aronson said.

Read more here.

Provided by the Florida Institute of Technology (via EurekAlert)

As polar ice melts, seabed life is working against climate change

When it comes to climate change, it's rare to get any good news. But a researcher who's reported evidence in the Cell Press journalCurrent Biology on September 21, after more than two decades of study, has some: the loss of sea ice over Antarctic waters in some areas has led to the increased growth of creatures living on the seafloor. Those underwater assemblages are acting as an important and unexpected carbon sink.

"It was a surprise that life had been invisibly responding to climate change for more than a decade below one of the most obviously visible impacts of climate change: the 'blueing' poles," says David Barnes of the British Antarctic Survey (BAS). "We've found that a significant area of the planet--more than three million square kilometers--is a considerable carbon sink and, more importantly, a negative feedback on climate change."

In fact, most of the known consequences of climate change have made matters worse instead of better. For example, Barnes says, as the polar climate warms, sea ice melts. As sea ice has melted, the Earth's surface has turned from reflective white to a much darker blue at the poles, absorbing more heat and melting even more ice.

Scientists knew that arctic forests and new algal blooms where ice shelves disintegrated were, to some extent, working against climate change. They now say, based on studies of West Antarctic bryozoans--organisms sometimes referred to as "moss animals"--that other organisms living on the seafloor "could be more important than both" when it comes to accumulating and burying carbon.

Antarctica has not experienced a net loss of sea ice in the way the Arctic has. The ice has melted over more-productive continental shelves as ice has formed over less-productive, deeper waters. In the new study, Barnes and his colleagues collected specimens across West Antarctic seas and used high-resolution images to calculate the density of life on the seabed.

Read more here.

Provided by Cell Press (via EurekAlert)

Take a Virtual Dive in a Kelp Forest | California Academy of Sciences

Historical data hold secrets of one of UK’s favourite fish

UK fisheries survey logbooks from the 1930s to 1950s have been digitised for the first time, revealing how cod responded to changing temperatures in the last century.

Scientists at the Centre for Environment, Fisheries and Aquaculture Science (Cefas) and the University of Exeter found that at the time, the warm seas experienced around Norway benefitted the cod, similar to the conditions there today.

Most cod eaten by the UK comes from northern seas including the Barents Sea around Norway, because the stocks there at the moment are at record highs. Cod stocks were also big in the middle of the last century, and this new research, published in PLOS ONE, reveals that the environmental conditions at the time contributed to the change. Cod diet data reveals that their food preferences each year, between capelin, herring, crustaceans and cod cannibalism, were also affected by their environment.

Cefas holds many records from historical survey cruises, many of them in the form of paper log books. A recent programme of work concentrated on cataloguing and digitising these documents, where possible, to ensure that they are not lost and can be made freely available. More of Cefas’ data, with the exception of data owned by industry, will continue to be made available over this year, as announced in June by the Environment Secretary, Elizabeth Truss.

The Barents Sea surveys were mainly carried out by the steam vessel RV Ernest Holt, which was commissioned especially to withstand Arctic conditions. These newly rescued data allow scientists to understand how fisheries in the region have responded to temperatures all the way from the 1930s to the present day.

The scientists at the time knew that the cod were being affected by their environmental conditions, but digitising this data has meant that much more modern techniques can be used to really delve into the responses of cod to changes in their environment and diet.

Read more here.

Provided by the University of Exeter

Restored streams take 25 years or longer to recover

New research has found that the number of plant species growing just next to restored streams can take up to 25 years to increase above those channelized during the timber floating era. This is according to doctoral student, Eliza Maher Hasselquist, and other researchers from Umeå University and the Swedish University of Agricultural Sciences (SLU), that was published in the journal Ecological Applications.

In the Vindel River catchment in northern Sweden, the main channel and most tributary streams were channelized from the 1850s to the 1950s to accommodate timber floating, which stopped in 1976. Boulders in the streams were blasted or pushed to the sides of the stream creating levees that disconnected the stream from the riparian zone. These streams began to be restored in the 1980s mostly for fish productivity, but these restorations have had impacts on other organism groups, particularly riparian plants. Riparian forests are important as they supply habitat, store carbon, provide shading, and filter water. These restorations have continued up through present day. This range in age of restored sites provided Eliza Maher Hasselquist and her colleagues’ a platform to study how fast stream communities recover with time after restoration.

“Northern Sweden is a great study system for determining the results of restoration because of the long history of restoration and the lack of urbanization. Most stream restoration in other parts of the world did not get started until the 1990s. So we have a unique opportunity to study the long-term effects of stream restoration,” says Eliza Maher Hasselquist.

Most stream restoration projects are not monitored, and those that are monitored are typically monitored for less than five years. The long-term outcomes of stream restoration have been relatively unknown. Eliza used 13 restored streams that represent a 25-year time span after restoration to determine how long after stream restoration it takes for plant species numbers to recover after restoration. She compared these restored streams to streams channelized for timber floating more than 50 years ago.

Read more here.

Intensity of desert storms may affect ocean phytoplankton

MIT study finds phytoplankton are extremely sensitive to changing levels of desert dust

Each spring, powerful dust storms in the deserts of Mongolia and northern China send thick clouds of particles into the atmosphere. Eastward winds sweep these particles as far as the Pacific, where dust ultimately settles in the open ocean. This desert dust contains, among other minerals, iron — an essential nutrient for hundreds of species of phytoplankton that make up the ocean’s food base.

Now scientists at MIT, Columbia University, and Florida State University have determined that once iron is deposited in the ocean, it has a very short residence time, spending only six months in surface waters before sinking into the deep ocean. This high turnover of iron signals that large seasonal changes in desert dust may have dramatic effects on surface phytoplankton that depend on iron.

“If there are changes to the sizes of deserts in Asia, or changes in the way people are using land, there could be a larger source of dust to the ocean,” says Chris Hayes, a postdoc in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS). “It’s difficult to predict how the whole ecosystem will change, but because the residence time [of iron] is very short, year-to-year changes in dust will definitely have an impact on phytoplankton.”

Read more here.

Provided by MIT

Seagrass thrives surprisingly well in toxic sediments - but still dies all over the world

Toxic is bad. Or is it? New studies of seagrasses reveal that they are surprisingly good at detoxifying themselves when growing in toxic seabed. But if seagrasses are stressed by their environment, they lose the ability and die. All over the world seagrasses are increasingly stressed and one factor contributing to this can be lack of detoxification.

Seagrass meadows grow along most of the world's coasts where they provide important habitats for a wide variety of life forms. However in many places seagrass meadows have been lost or seriously diminished and in several places, researchers and authorities work hard to understand what is happening and prevent the seagrasses from disappearing.

Now biologists from SDU add another important piece to the understanding of sea grass life.

It has long been known that the toxin sulphide is part of the threat to seagrasses. Sulphide is a naturally occurring toxin found in the seabed where seagrasses grows. The seabed is characterized by lack of oxygen and a smell of rotten eggs from sulphides.

A widely held theory states that seagrasses cannot tolerate sulphide and that increasing amounts of sulphide due to increased pollution have a negative effect on seagrasses.

Sulfide is absorbed by plant tissue

"But our research shows that seagrasses are actually capable of protecting themselves from sulphide. In fact, seagrasses benefits from sulphide”, explains postdoc Harald Hasler-Sheetal who has conducted the research together with Professor Marianne Holmer, both from the Department of Biology, University of Southern Denmark.

against app. two thirds of the sulphide that enters the plant from toxic seabed. The last third is absorbed by the plant’s tissue and here enzymes convert the sulphide into beneficial nutrients.

But the discovery that a seagrass can protect itself from sulfide does not mean that all is good.

"Seagrasses cannot tolerate sulphide under all circumstances. If a seagrass is stressed, the plant's capacity to detoxify itself will weaken, and the plant will be less capable of protecting itself from sulphide. It's like when humans are stressed; then we cannot perform optimally. Stressed seagrasses grow slower and may die back – this is what we see in many parts of the world", explains Harald Hasler-Sheetal.

Read more here.

UT Arlington-led research reveals new details about the immunity of sea stars dying along the West Coast

A study led by a University of Texas at Arlington graduate student examining sea stars dying along the West Coast provides new clues about the starfish’s immune response and its ability to protect a diverse coastal ecosystem.

Lauren Fuess, a Ph.D. candidate in quantitative biology, and her team looked at the wasting disease responsible for the largest die-off of sea stars ever recorded. Scientists believe that a virus related to rabies causes wasting disease. When infected, the stars’ arms contort, and they develop white lesions. The normally rigid stars begin to melt and become squishy in the final stages of the disease. 

Wasting disease affects nearly 20 different species and it has caused up to almost 90 percent mortality in some areas off the West Coast over the last two years. 

“The sea stars protect the rocky shores, keeping them from becoming dominated by mussels,” Fuess said. “When you remove the sea stars, you see dramatic declines of other species, so basically you go from a diverse ecosystem to a mussel-coated beach.” 

The team researched the project looking at transcriptomes, or the molecules expressed from the genes, of sea stars infected with wasting disease as part of an Ecology of Infection Marine Disease course last summer at Friday Harbor Laboratories at the University of Washington.

Fuess, who recently received a National Science Foundation Graduate Research fellowship, works in the laboratory of Laura Mydlarz, a UT Arlington associate professor of biology. 

“We’re looking at an increasing rate of diseases that may be linked to climate change as well as pollution in the ocean,” Mydlarz said. “What we’re working on at our field sites and here at UT Arlington is looking to see if some of this temperature stress due to climate change or pollution are causing the animals, such as the sea stars and the corals, to be more susceptible to diseases.”

Read more here.