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In This Issue

• Well Sealed, But Remaining Oil in Gulf Threatens Sea Life
• Freshwater Toxin Linked to Sea Otter Deaths
• Walruses at Risk from Shrinking Arctic Sea Ice
• Antibiotic-Resistant Bacteria Found in Predatory Fish

Science in the News

Well Sealed, But Remaining Oil in Gulf Threatens Sea Life

The dwarf seahorse, a species endemic to the Gulf of Mexico, is at risk from the oil and dispersants that remain below the Gulf's surface. John G. Shedd Aquarium, Chicago

Roughly five months after the blowout of the Deepwater Horizon oil well in the Gulf of Mexico, the well was permanently sealed this past weekend, according to U.S. officials. However, despite an August 4 report by the National Oceanic and Atmospheric Administration (NOAA) indicating that 74 percent of the oil spilled in the blowout has been recovered, evaporated or dispersed, results from further tests in the Gulf of Mexico have scientists concerned that a significant amount of the oil remains below the surface.

While a substantial portion of the oil has degraded because of the Gulf's high numbers of natural oil-eating bacteria, a team of researchers in the Gulf announced to the Associated Press last week they had found oil two inches thick on the sea floor blanketing a layer of dead shrimp and other small animals. Ten of the 14 samples taken by the researchers contained visible oil, with some oiled samples taken as far as 80 miles from the Deepwater Horizon well.

One animal that may be at a significant risk from the residual oil is a tiny species of seahorse unique to the Gulf called the dwarf seahorse (Hippocampus zosterae). Dwarf seahorses, which dwell in the Gulf's seagrass beds, produce very few young, making them extremely sensitive to environmental change. Project Seahorse, an international seahorse conservation organization, issued a release on September 7 warning that the dwarf seahorse faces the possibility of extinction because the spill and cleanup have destroyed its habitat and toxic dispersants have accumulated in its food sources.

"We're very worried," said Amanda Vincent, director of Project Seahorse at the University of British Columbia, in the release. "All of the seahorse populations in the area will be affected, but the dwarf seahorse is at greatest risk of extinction because much of its habitat has been devastated by the spill."

Project Seahorse advised that seahorses and other marine life would be better protected if cleanup efforts avoid the use of chemical dispersants and the burning of oil slicks, which destroy seagrasses. Instead, it recommended the use of booms to isolate slicks, which can then be captured, left to evaporate or broken up with biological agents such as fertilizers.

"It's absolutely critical that measures be taken to preserve the seagrass mats and beds," said Heather Masonjones, a seahorse biologist at the University of Tampa, in the release. "We must act quickly and carefully to give these fragile species the best chance of survival."

For Further Information: See Project Seahorse at http://seahorse.fisheries.ubc.ca/

Stay on top of the latest information about the spill by visiting SeaWeb's Deepwater Horizon Oil Spill Comprehensive Resource Center, providing news updates, SeaWeb briefings and links to external resources.

Contact: E-mail Project Seahorse regarding the release at t.stiem@projectseahorse.org

Science Briefs

Freshwater Toxin Linked to Sea Otter Deaths

Toxins from cyanobacteria blooms have entered the Pacific marine environment, threatening Southern sea otters, such as the pup shown here. Randy Wilder, Monterey Bay Aquarium

The deaths of 21 southern sea otters, a federally protected species, were caused by toxins from freshwater blooms of cyanobacteria that entered the marine environment, according to a recent study in the journal PLoS ONE. The findings present the first documented deaths of marine mammals due to cyanotoxins and verify the existence of a new danger to the Pacific coastal environment.

"Super-blooms" of cyanobacteria, formerly known as blue-green algae, are an emerging problem in freshwater environments. Spurred on by high temperatures, elevated nutrient levels and other factors, such blooms produce high amounts of natural cyanotoxins, such as microcystins, that are entering marine ecosystems via watersheds and eventually reaching sea otters, likely through invertebrate food sources, write Melissa Miller with the California Department of Fish and Game and colleagues.

The researchers performed necropsies on sea otters recovered along the shore of Monterey Bay in central California, finding they suffered liver failure as a result of exposure to cyanotoxins. They confirmed that cyanobacteria blooms were present in Pinto Lake, a recreational water body slightly inland of Monterey Bay, and also found that three rivers flowing into the bay were carrying microcystins.

Carcasses of the poisoned otters were commonly recovered near river mouths and harbors, suggesting that their food—such as oysters, clams and mussels—was the source of contamination. In laboratory tests, oysters, clams, mussels and sea snails exposed to the cyanobacteria showed significant bioconcentration of the toxins, with the bivalves also slow to cleanse the toxins from their system. As these bivalves are common food sources for marine species and humans, the researchers' findings provide "the first hint of a serious environmental and public health threat that could negatively impact marine wildlife and humans," the authors write.

Source: Miller M.A. et al. 2010. Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters. PLoS ONE 5(9): e12576.

Contact: Melissa Miller, California Department of Fish and Game. E-mail: mmiller@ospr.dfg.ca.gov

Walruses at Risk from Shrinking Arctic Sea Ice

A widespread retreat of Arctic sea ice this summer has pushed walrus populations onto Alaska's coastline. U.S. Geological Survey

In recent weeks, tens of thousands of walruses have flocked to the coastline of Alaska's Chukchi Sea, an unusual occurrence that has scientists worried for their future. The behavior is a result of the widespread retreat of sea ice, critical habitat for the species, which is at its second lowest extent in the satellite record, according to the National Snow and Ice Data Center.

According to a recent study by scientists with the U.S. Geological Survey (USGS) the Pacific walrus has a 40 percent chance of being classified as vulnerable, rare or extinct by the year 2095. In arriving at this conclusion, researchers conducted population modeling to estimate the impact of a variety of factors on the species.

In the model, sea ice habitat loss and subsistence hunting by Native Alaskan and Russian communities had the greatest influence on future Pacific walrus populations. The researchers used sea ice projections that anticipate ice-free conditions over the entire shelf during the summer and fall months by the end of the century, accompanied by earlier melt in spring and delayed freeze-up in late fall. Subsistence hunting could exacerbate the adverse effects of future sea ice conditions because while a decrease in numbers taken would likely lead to a negligible positive effect on walrus populations, increased or even steady levels of hunting could have a significant negative impact. "If in the future, the walrus population declines, but a constant number of walruses continue to be harvested, the level of stress by the harvest would effectively increase," the researchers write.

Additional stressors on the Pacific walrus such as ocean acidification and increased levels of contact with humans had smaller influences on population estimates in the model, mostly due to the variable nature of these pressures and a poor scientific understanding of their potential effects on walrus abundance.

Source: Jay, C.V., Marcot, B.G. and Douglas, D.C. 2010. Projected status of the Pacific walrus (Odobenus rosmarus divergens) in the 21st century. U.S. Geological Survey.

Contact: Chadwick Jay, U.S. Geological Service. E-mail: cjay@usgs.gov

Antibiotic-Resistant Bacteria Found in Predatory Fish

Researchers found antibiotic-resistant bacteria in various species of predatory fish, such as the lemon shark pictured here. Sarah Lardizabal/MarinePhotobank

Researchers have discovered antibiotic-resistant bacteria in various species of predatory fish in a range of geographic locations, confirming a troubling trend that could pose a health hazard to humans.

Antibiotic resistance in bacteria, a rising problem in human and veterinary medicine, has been widely documented in humans and domesticated species. Few studies, however, have been conducted to analyze the prevalence of antibiotic-resistant bacteria in wild animals, particularly top-level predatory fish.

To examine this, Jason Blackburn of the University of Florida and colleagues took bacteria samples of seven species of sharks and a redfish at six study sites in coastal waters of Belize, Louisiana, the Florida Keys and Massachusetts. After isolating the bacteria, the researchers treated the samples with 13 drugs with antibacterial properties. Antibiotic-resistant bacteria were found in all populations of the animals tested in the study, with shark samples in the Florida Keys exhibiting the highest resistance to a number of the drugs.

Writing in a recent issue of the Journal of Zoo and Wildlife Medicine, the authors state, "The marine environment may be considered a reservoir for resistance to such drugs, and future surveillance of predatory fishes should continue." The researchers note that some samples they had taken in Florida and Belize were in close proximity to septic and sewage facilities. They assert that raw sewage and sludge could be the source of some strains of drug-resistant bacteria such as E. coli. Another potential source could be agricultural runoff, which is a particular concern in the Mississippi River, a primary source of pollution to water quality in the northern Gulf of Mexico, they observe.

"Because fisheries remain an important component of the human diet, this information may be used to determine zoonotic health risks," they conclude.

Source: Blackburn, J.K. et al. 2010. Evidence of antibiotic resistance in free-swimming, top-level marine predatory fishes. Journal of Zoo and Wildlife Medicine 41(1): 7–16.

Contact: Jason Blackburn, University of Florida. E-mail: jkblackburn@ufl.edu

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