Friday, July 2, 2010

Nutrients, viruses, and the biological carbon pump

Phytoplankton seen under a microscope.

Southampton, UK (SPX) Jul 02, 2010 - Adding nutrients to the sea could decrease viral infection rates among phytoplankton and enhance the efficiency of the biological pump, a means by which carbon is transferred from the atmosphere to the deep ocean, according to a new mathematical modelling study.

The findings, published in the Journal of Theoretical Biology, have implications for ocean geo-engineering schemes proposed for tackling global warming.

Tiny free-floating algae called phytoplankton dominate biological production in the world's oceans and sit at the base of the marine food web. Their population dynamics are controlled by sunlight, nutrient availability, grazing by tiny planktonic animals (zooplankton) and mortality caused by viral infection.

"Viruses are the most abundant organism in the world's oceans, and it is thought that all phytoplankton species are susceptible to infection. Our aim was to model the interaction between viruses, phytoplankton, zooplankton grazing and nutrient levels," said Dr Adrian Martin of the National oceanography Centre (NOC), who collaborated in the project with Dr Christopher Rhodes, a bio-mathematician at Imperial College London.

The researchers took an 'eco-epidemic' modelling approach, taking into account the mutual interaction between the effects of ecology and disease epidemiology. This approach has been used previously to model the effects of infection by pathogens on the population dynamics of mammals and invertebrate animals. …

The models predict that decreased nutrient levels correspond to high viral infection rates among phytoplankton.

On the other hand, increased nutrient levels are predicted to decrease viral infection rates. This means that more of the carbon contained in phytoplankton would be available to zooplankton and other creatures higher up the food chain.

When these organisms die, a proportion of the associated carbon would sink down to the deep ocean, where it could be locked away for centuries, rather than being released back to the atmosphere as carbon dioxide. This mechanism for exporting carbon to the deep ocean is called the biological carbon pump. …

Nutrients, Viruses And The Biological Carbon Pump

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