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In This Issue

• Gulf of Mexico among Most Biologically Diverse Regions, Still at Risk from Oil
• Studies Shine Light on Phytoplankton Growth, Risk from Global Warming
• Researchers Discover New Species Near Great Barrier Reef

Science in the News

Gulf of Mexico among Most Biologically Diverse Regions, Still at Risk from Oil

Despite White House assurances that as much as 75 percent of the oil from the Deepwater Horizon accident has been removed from the Gulf of Mexico, through evaporation, skimming and controlled burns such as this one, some independent researchers argue that at least half the oil remains in the ecosystem. John Kepsimelis, U.S. Coast Guard/Marine Photobank

The Gulf of Mexico is among the most biologically diverse marine regions on Earth, according to the latest report from the Census of Marine Life (CoML), a determination that researchers say serves to underline concerns about the impacts on the region of the Deepwater Horizon oil spill.

CoML is a global network of researchers in more than 80 nations engaged in a 10-year scientific initiative to assess and explain the diversity, distribution and abundance of life in the ocean. Its most recent study, a "roll call" of species in 25 key marine areas, was published in August in the open-access journal PloS One.

The study found that the waters around Australia contained the greatest diversity of marine species, but the Gulf of Mexico ranked fifth, both in total species (15,374) and the number of species relative to area (approximately 10 per square kilometer, or two-fifths of a square mile).

Such high diversity shows that the Gulf "is more threatened than we thought it was" by the oil spill and other human activities, said Mark Costello of the Leigh Marine Laboratory at the University of Auckland in New Zealand.

The CoML announcement came a day before a new study from the U.S. Geological Survey and the U.S. Department of Energy confirmed that the Deepwater Horizon spill was the largest accidental spill of oil in the ocean in history. In total, close to 206 million tons gushed from the well, more than 18 times more oil than spilled when the Exxon Valdez ran aground in Alaska's Prince William Sound in 1989.

Last week, more than 100 days after oil began gushing, BP succeeded in "killing" the well, injecting mud to drive the oil far under the seabed. By mid-August, it expects to have completed a relief well, which will perform much the same task and provide insurance that the well will not leak again.

Superficially, much of the Gulf is showing few remaining signs of the spill, several weeks after BP installed a cap on the wellhead on July 15. A July 29 story in the International Herald Tribune noted the presence of "only a few patches of sheen and an occasional streak of thicker oil. Radar images taken since then suggest that these few remaining patches are quickly breaking down in the warm surface waters of the Gulf."

Less oil on the surface "does not mean that there isn't oil beneath the surface, however, or that our beaches and marshes are not still at risk," Jane Lubchenco, administrator of the National Oceanic and Atmospheric Administration (NOAA), cautioned in a briefing on July 27. However, one week later, NOAA and the Department of the Interior released a report stating that 75 percent of the oil from the accident had either evaporated, or been skimmed, burned or dispersed; the remaining 25 percent "is either on or just below the surface as residue and weathered tarballs, has washed ashore or been collected from the shore, or is buried in sand and sediments."

Not everyone agreed with that assessment. "Recent reports seem to say that about 75 percent of the oil is taken care of and that is just not true," John Kessler of Texas A&M University told The Guardian newspaper in Britain. "The fact is that 50 percent to 75 percent of the material that came out of the well is still in the water. It's just in a dissolved or dispersed form."

For Further Information: More information about the biodiversity of the Gulf of Mexico is available in: Felder, D.L., and D.K. Camp, eds. 2009. Gulf of Mexico: Origin, Waters and Biota. Volume 1: Biodiversity. Galveston, Texas: TAMU Press.

For Further Information: 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.

Science Briefs

Studies Shine Light on Phytoplankton Growth, Risk from Global Warming

A long-accepted theory to explain spring blooms of phytoplankton, such as this one off Argentina, is incorrect, says a new analysis. NASA, Modis Rapid Response Team

A long-accepted theory of why phytoplankton, the building block of ocean ecosystems, blooms in the spring is incorrect, according to a new analysis in the journal Ecology.

For more than 50 years, the "critical depth hypothesis" stated that phytoplankton bloom in temperate oceans in the spring because days are longer and brighter and the surface layer is warmer than in fall and winter months. According to this theory, because warm water is less dense than cold water, springtime warming creates a surface layer that essentially "floats" on top of the cold water below, slows wind-driven mixing and holds the phytoplankton in the sunlit upper layer more of the time, letting them grow faster.

But the new study, based on a nine-year analysis of satellite records of carbon and chlorophyll data by Michael Behrenfeld of Oregon State University, found that phytoplankton accumulation actually begins in the depths of winter. What happens, says Behrenfeld, is that winter storms cause mixing of the biologically rich surface layer and colder, deeper water, diluting concentrations of both phytoplankton and the zooplankton that would normally eat them, allowing greater numbers of phytoplankton to avoid predation. By springtime, the storms subside, and even as increasing sunlight allows phytoplankton growth to surge, predation by zooplankton increases and keeps phytoplankton numbers in check.

According to Behrenfeld, the study shows that wintertime mixing of ocean layers is at least as important to phytoplankton growth as the rate of phytoplankton photosynthesis. This is a concern, because as the ocean warms from climate change, it is expected to become more stratified, preventing such mixing.

A separate study in the journal Nature emphasized the threat to phytoplankton posed by a warming ocean. Using a combination of satellite and historical data, Daniel Boyce and colleagues from Dalhousie University concluded that between 1899 and 2008, phytoplankton declined by approximately 1 percent of the global average per year. The declines, they write, are "unequivocal": they are related to increased sea surface temperature during the last century, and are "consistent with the hypothesis that increasing ocean warming is contributing to a restructuring of marine ecosystems."

Sources: Behrenfeld, M.J. 2010. Abandoning Sverdrup's Critical Depth Hypothesis on phytoplankton blooms. Ecology 91(4): 977-989; Boyce, D., et al. 2010. Global phytoplankton decline over the past century. Nature 466: 591-596.

Contact: Michael J. Behrenfeld. Oregon State University. E-mail: mjb:science.oregonstate.edu; Daniel G. Boyce, Dalhousie University. E-mail: dboyce@dal.ca

Researchers Discover New Species Near Great Barrier Reef

Researchers from the University of Queensland filmed several previously unknown species of fish and other marine wildlife using deep-sea cameras near the Great Barrier Reef. Justin Marshall, Queensland Brain Institute

Australian researchers say they have discovered a number of previously unknown species in deep water off the Great Barrier Reef.

Using deep-sea cameras, a team from the University of Queensland recorded "prehistoric six-gilled sharks, giant oil fish, swarms of crustaceans and many unidentified fish," according to a statement on the university website. The team, led by Professor Justin Marshall, captured the sea creatures using special low-light sensitive, custom-designed remote controlled cameras, which sat on the seafloor.

"Osprey Reef is one of the many reefs in the Coral Sea Conservation Zone, which has been identified as an area of high conservation importance by the Federal Government. Therefore, it is paramount that we identify the ecosystems and species inhabiting the area," Marshall said in the statement. "We simply do not know what life is down there and our cameras can now record the behavior and life in Australia's largest biosphere, the deep sea."

In September the scientists will travel to the Peruvian Trench off South America, where they will film and capture deep-sea species 6,600 feet (2,000 meters) below sea level.

Team member Kylie Greig said the trip would help shed light on how deep-sea creatures had evolved over time: "This technology will help the discovery of deep-sea creatures' adaptations to the challenges of living at crushing depths and in freezing and dark water. Here they must find food and mates in the dark and avoid being eaten themselves. We are interested in the sensory systems used for this lifestyle," she said.

For Further Information: Information about the findings, including photographs, as well as contact information, is available at www.qbi.uq.edu.au/index.html?page=137977

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