10 March 2008

Ocean deserts

The world oceans are deeply affected by human activities, from pollution to resource overexploitation, but now there is a new problem.

The least biologically productive areas of the oceans are expanding much faster than predicted. This is the result of a new study conducted by researchers at the National Oceanic and Atmospheric Administration (NOAA) and the University of Hawaii.

The evidence of this expansion comes from data collected by a visual satellite sensor that reads reflective colour to measure the density of chlorophyll in phytoplankton, the microscopic organisms that are the base of the marine food web. Atlantic and Pacific Oceans are characterized by huge 'black' spots, which indicate zones of very low productivity. These zones, likened to deserts, now cover an estimated 51 million square kilometres in the two oceans and are replacing very fast adjacent prolific areas.

This change in ocean biology, probably linked to the warming of sea surface waters, can have deep consequences to all marine ecosystems. It may negatively affect all the marine food web from plankton to fishes, turtle and cetaceans.

Silvia Bonizzoni

(The image by NOAA shows black areas considered the least biologically productive)

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