Wednesday, May 26, 2010

ry'leh stirs....,


Video - Ryleh.

The Scientist | Last month's blowout of British Petroleum's Deepwater Horizon oil well -- which caused the US Commerce Department to decree today (25th May) that fisheries in three states bordering the Gulf of Mexico are official disasters -- is likely already impacting the Gulf's microscopic denizens, which will, in turn, have long-term effects on commercially important species such as fish and shrimp, scientists say.

Images of oil-soaked sea gulls and tar coated turtles, which typically follow major oil spills, are starting to materialize in the Gulf, but bacterial populations are likely to boom in response to the release of millions of gallons of oil, Monty Graham, biological oceanographer at the Dauphin Island Sea Lab off the coast of Alabama, told The Scientist.

Bacteria could benefit from the oil spill, Graham argued, because some bacterial species and lineages view a massive oil spill as a veritable cornucopia of delicious hydrocarbons, not a catastrophe.

The boon to bacteria most likely has ramifications that will ripple throughout marine food webs in the Gulf, especially at prominent nodes where commercially important species such as fish, crabs, and shrimp, reside. What those ramifications are, however, remain as murky as the huge plumes of oil recently discovered hovering just below the surface of Gulf waters.

Researchers who study microbial and planktonic ecosystems in the Gulf of Mexico are anxiously anticipating the effects of what may be the biggest oil spill ever. Recently uncovered evidence of oxygen depletion near those plumes (an indication that bacterial respiration is occurring en masse) indicate that a bacterial bloom is ramping up.

Normally in the Gulf, as in other oceanic ecosystems, the base of the food web is provided by photosynthetic, one-celled organisms called phytoplankton. Sunlight fuels phytoplankton growth, small crustaceans called copepods dine on phytoplankton, fish larvae (and larvae from other species) dine on copepods, small fish dine on larval organisms, and so forth and so on.

Bacteria normally exist in a semi-self-contained food web called the "microbial loop." But if they expand dramatically, these new gobs of organic matter could attract hungry, one-celled heterotrophs called nanoflagellates, which could feed slightly larger ciliates, which would then be fed upon by copepods, thus entering the normal food web that ends in commercially or recreationally important species, such as the Red Drum. In theory, this extra organic matter could help compensate for the loss of phytoplankton, since photosynthesis rates (and thus phytoplankton) may decline due to decreased sunlight penetration through oily water. However, by the time that bacteria-driven energy reaches the upper trophic levels of the food web, it has gone through more steps along the way than the energy stemming from phytoplankton. Since energy is lost at each level, adding extra levels means less energy makes its way to the big eaters.

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