Ocean plants like it cold, thanks

A warmer climate could disrupt the marine food chain, new research from NASA suggests, potentially damaging fisheries and other marine ecosystems.

The space agency's researchers tracked temperature and marine plant growth over a period of nine years, beginning in 1997 when the OrbView-2 satellite was launched. Their research has revealed a link between higher global temperatures and lower production of microscopic phytoplankton, the primary oceanic food supply. Conversely, cooler weather saw the phytoplankton thrive.

Phytoplankton are hugely important in regulating the amount of carbon in the atmosphere - they account for as much photosynthesis as all land plants combined.

Naturally, if fewer of the microscopic marine plants can grow, photosynthesis is less, and the plants take in less carbon. This, NASA researchers say, means more carbon is left in the atmosphere to contribute to the overall process of global warming.

"Rising levels of carbon dioxide in the atmosphere play a big part in global warming," said lead author Michael Behrenfeld of Oregon State University.

"This study shows that as the climate warms, phytoplankton growth rates go down and along with them the amount of carbon dioxide these ocean plants consume. That allows carbon dioxide to accumulate more rapidly in the atmosphere, which would produce more warming."

The team explains the link by analysing the changes to the ocean that go hand in hand with changes in atmospheric temperature.

As the climate warms, so do the upper layers of the ocean. The warmer, lighter water floats on top of a much denser layer of cooler water below. This stratification effectively cuts the surface layer off, and in so doing, prevents the phytoplankton from accessing the nutrients they need to thrive. ®