Worried about the future of some marine species or other? Well, noble though your concerns are, there could be a much more emphatic disaster looming.

We've got to hope they're wrong, but research scientists have warned that marine life around the world could be severely reduced in centuries to come - due to a major reduction in microscopic plankton, which lie at the base of the marine food chain.

In a study published by Nature magazine and reported by Britain's Independent newspaper, the scientists calculated that seas warmed by global warming will greatly limit the rise of nutrients from the deep.

Increasing vertical temperature differentials will inhibit the mixing of materials across aquatic thermoclines, so that microscopic plankton cannot move upward to the depths at which so many marine species have evolved.

Plankton's plant form, phytoplankton, survives particularly well at a depth of about 100m. It absorbs carbon dioxide and sunlight to produce organic carbon, a basic food. But without plankton rising upward to support the food chain at shallower depths, the result could be devastating for marine life in oceans' higher reaches.

It was also calculated that a reduction in phytoplankton at shallower levels would decrease the sea's ability to absorb carbon dioxide from the atmosphere. The higher atmospheric levels which result would accelerate global warming even further.

Professor Jef Huisman of the University of Amsterdam, who led the research team, produced a computer model for phytoplankton movement which proved accurate when tested against measurements from parts of the Pacific where upper sea temperatures are higher than elsewhere in the world.


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