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December 14, 2010, Vol. 15, No. 25
Turtle banner image: Claire Fackler, NOAA National Marine Sanctuaries

In This Issue

Science in the News

World Running Out of Places to Fish

Fishing boatsA new study has found that the commercial fishing industry has expanded its range so widely that only a few areas of the high seas and some waters around Antarctica remain largely unfished. Wolcott Henry/Marine Photobank

The growth of the commercial fishing industry during the last several decades has been driven by relentless expansion into new fishing grounds. As a result, concludes a recent study, fisheries now cover a majority of the world's ocean, and there are very few areas remaining into which the fishing industry can expand farther.

Writing in the online open-access journal PLoS One, Wilf Swartz of the University of British Columbia and colleagues found that fisheries expanded at a rate of 386,000 square miles (one million square kilometers) per year from the 1950s to the end of the 1970s before more than tripling their rate of expansion in the 1980s and early 1990s. Between 1950 and 2005, the spatial expansion of fisheries started from the coastal waters off the North Atlantic and Northwest Pacific, reached into the high seas and southward into the Southern Hemisphere at a rate of almost one degree of latitude per year. It was accompanied by a nearly five-fold increase in catch, from 19 million metric tons in 1950, to a peak of 90 million metric tons in the late 1980s and dropping to 87 million metric tons in 2005.

“The decline of spatial expansion since the mid-1990s is not a reflection of successful conservation efforts but rather an indication that we've simply run out of room to expand fisheries,” said Swartz in a press release to announce the study.

The authors conclude that only unproductive waters of high seas and relatively inaccessible waters in the Arctic and Antarctic remain as commercial fishing's final frontiers. They say that the rapidly diminishing number of available fishing grounds indicates a global limit to growth and highlights the urgent need for a transition to sustainable fishing.

Source: Swartz, W. et al. 2010. The spatial expansion and ecological footprint of fisheries (1950 to present). PLoS One 5(12): e15143. doi:10.1371/journal.pone.0015143 .

Contact: Daniel Pauly, University of British Columbia. E-mail: d.pauly@fisheries.ubc.ca

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Science Briefs

Ocean Crust Rich With Microbial Life

Research Vessel Joides ResolutionA drill rig on the research vessel Joides Resolution prepares to dig deep into the ocean crust. Researchers from Oregon State University have found microbial life forms living in the crust that are apparently feasting on hydrocarbons. Amber Harris

Scientists have found an unexpectedly abundant amount of bacterial life more than 4,600 feet (1,400 meters) below the seabed, a discovery that has ramifications for the search for life on Mars and strategies for adapting to climate change on Earth.

Writing in the open-access, online journal PLoS One, Olivia Mason of Oregon State University and colleagues point out that although the geology of oceanic crust has been extensively studied, its biology has not—partly because digging to such depths poses logistical and financial challenges and partly because expectations of finding rich biological life in the crust have been limited.

In most areas, the deepest layer of ocean crust, known as the gabbro layer, doesn't even begin until the crust is about two-miles (3,200-meters) thick. But at a site in the Atlantic Ocean near an undersea mountain, the Atlantis Massif, gabbro rock formations are closer to the surface than usual because they have been uplifted and exposed by faulting. Mason and colleagues took advantage of this feature to drill into comparatively shallow depths and study the microbiology of the crust.

Perhaps not surprisingly given the depth and extreme conditions, although the researchers found microbial life, it was not at high density. The microbes that were there, however, showed some interesting adaptations to life in those extreme conditions. Some were degrading hydrocarbons, some appeared to be capable of oxidizing methane, and others contained genes for fixing, or converting from a gas, both nitrogen and carbon. Interestingly, analysis of the hydrocarbons suggests that they originate from deep within the crust, suggesting that the microbial ecosystem is operating entirely independently of the surface biosphere.

The findings are also of interest because little is known about the role the deep ocean crust may play in carbon storage and fixation. Increasing levels of carbon dioxide, a greenhouse gas when in the atmosphere, in turn raises the levels of carbon dioxide in the ocean.

But if these microbes are indeed able to fix carbon, the researchers say their findings may lend credence to one concept for reducing carbon emissions in the atmosphere, by pumping carbon dioxide into deep subsurface layers where it might be sequestered permanently.

The researchers also noted that methane found on Mars could be derived from geological sources, and concluded that subsurface environments on Mars where methane is produced could support bacteria like those found in this study.

“These findings don't offer any easy or simple solutions to some of the environmental issues that are of interest to us on Earth, such as greenhouse warming or oil spill pollution,” said Martin Fisk of Oregon State University in a press release to announce the findings. “However, they do indicate there's a whole world of biological activity deep beneath the ocean that we don't know much about, and we need to study.”

Source: Mason, O.U. et al. 2010. First investigation of the microbiology of the deepest layer of ocean crust. PLoS One 5(11): e15399. doi:10.1371/journal.pone.0015399

Contact: Steve Giovannoni, Oregon State University. E-mail: steve.giovannoni@oregonstate.edu

Mixtures of Organic Pollutants Can Affect Phytoplankton Abundance

Phytoplankton
Researchers have found toxic chemical pollution may affect the abundance of marine phytoplankton (such as these diatoms) more than previously anticipated. Gordon T. Taylor, Stony Brook University/NOAA

Persistent organic pollutants (POPs) may impact the abundance of phytoplankton in the ocean at lower levels than previously considered, as their impact appears to be greater in combination than in isolation.

Writing in the journal Chemosphere, Pedro Echeveste of the Institut Mediterrani d’Estudis Avançats and colleagues note that POPs are frequently carried long distances in the atmosphere until they become deposited via precipitation into the ocean. There, they accumulate in phytoplankton and thus become transported through the oceanic food web. The consequences of that bioaccumulation on higher trophic levels—concentrations in and impacts on marine mammals such as polar bears, seals and whales—have been relatively well studied. The effects on phytoplankton communities, however, are less well known.

Echeveste and colleagues took samples of water and phytoplankton from the northeast Atlantic during a research cruise, studied the levels of pollutants in the water and exposed the phytoplankton to various organic pollutants. They found that certain single pollutants proved lethal to phytoplankton only at levels far higher than those they found in the ocean. However, mixtures of organic pollutants proved to have a toxic effect on phytoplankton abundance and vitality as well as on concentrations of the chlorophyll that phytoplankton need to photosynthesize at much lower levels. In fact, levels of toxicity of POP mixtures proved a thousand times greater than would be expected for individual compounds.

The authors conclude that their results show the need for a far broader examination of the impacts of POPs on marine environments, considering their effect in totality rather than as individual pollutants.

Source: Echeveste, P., et al. 2010. Decrease in the abundance and viability of oceanic phytoplankton due to trace levels of complex mixtures of organic pollutants. Chemosphere 81: 161-168.

Contact: Jordi Dachs, IDAEA-CSIC, Spain. E-mail: jordi.dachs@idaea.csic.es.


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Banner image credit: Claire Fackler, NOAA National Marine Sanctuaries