Monday, March 23, 2009

Aerosols can poison plankton

Environmental Research Web: For many years, researchers have believed that atmospheric aerosols can dissolve into the oceans and provide phytoplankton with nutrients beneficial to their growth, such as iron and phosphates. But now a team from the US and Israel has found that some aerosols can actually harm the micro-organisms.

"This is the first time that a toxicity effect from aerosols in the ocean is seen and it highlights the complexity of the system – basically we cannot treat aerosols as all being the same and we cannot treat phytoplankton as all responding similarly to aerosol inputs," Adina Paytan of the Univeristy of California, Santa Cruz told environmentalresearchweb. "We will have to think about the balance between the benefits and the negative impacts of aerosols. This is particularly important since it is likely that aerosol deposition amount and composition will change with climate change and increased urbanization."

Paytan and colleagues from Stanford University, Woods Hole Oceanographic Institution, Cornell University, the United States Geological Survey, and the Interuniversity Institute of Marine Sciences in Israel studied phytoplankton in the northern Red Sea. Aerosols from a European air mass boosted phytoplankton growth, whereas aerosols from an air mass from the Sahara Desert decreased the growth of picoeukaryotes and Synechococcus but not Prochlorococcus.

The researchers believe this may be due to increased levels of copper in the African air mass. Copper is present in the atmosphere from both natural sources, such as desert dust, and from industrial sources such as combustion.

"It is a well accepted paradigm in marine sciences that atmospheric input of aerosols to the ocean provides vital nutrients to the ocean but I realized that very little direct evidence showing that exists," said Paytan. "Specifically there were no data regarding what in the aerosols exactly impacts the organisms and how specific organisms in a community respond. I did not expect to see toxicity and indeed in most experiments I saw growth of the phytoplankton except when I decided to look at the response to aersols with a different chemical makeup."…

Phytoplankton swirls in the Arabian Sea

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