Earthsky Interviews
Private: Warming ocean surface threatens marine food chain
July 22, 2007 - Biodiversity
In turn, that could mean trouble for all ocean life. Scientists have charted a gradual warming of the ocean surface throughout the world. David Siegel, a professor of marine science at the University of California, Santa Barbara, has found that warmer surface water limits the growth of phytoplankton.
Phytoplankton use carbon dioxide, light, and nutrients to reproduce. The nutrients they need are dredged up from the deeper ocean. But warmer surface water creates greater density in the deep ocean, so it’s harder for wind and currents to bring nutrients from the ocean depths to the surface.
Fewer nutrients mean shrinking phytoplankton populations. In turn, this affects other marine creatures, since these phytoplankton form the base of the marine food chain.
David Siegel: _All the food webs, where it goes into the zooplankton that eat the phytoplankton, and the small fishes that eat the zooplankton, the big fishes that eat the small fishes . . . all that’s dependent on how much energy gets put into the food web._
Siegel speculates that as oceans continue to warm up, phytoplankton numbers will continue to drop. What the long-range consequences will be for all ocean life, said Siegel, is still poorly understood.
Thanks today to “NASA”:http://www.nasa.gov: explore, discover, understand.
*Our thanks to:*
David Siegel
Professor of Marine Science
University of California
Santa Barbara