“Microscopic life crucial to the marine food chain is dying out. The consequences could be catastrophic.”
July 29, 2010
Scientists may have found the most devastating impact yet of human-caused global warming — a 40% decline in phytoplankton since 1950 linked to the rise in ocean sea surface temperatures. If confirmed, it may represent the single most important finding of the year in climate science.The headlines above are from an appropriately blunt article in The Independent about the new study in Nature, “Global phytoplankton decline over the past century” subs. req’d. Even the Wall Street Journal warned, “Vital Marine Plants in Steep Decline.” Seth Borenstein of the AP explains, “plant plankton found in the world’s oceans are crucial to much of life on Earth. They are the foundation of the bountiful marine food web, produce half the world’s oxygen and suck up harmful carbon dioxide.”We’ve known for a while that we are poisoning the oceans and that human emissions of carbon dioxide, left unchecked, would likely have devastating consequences — see “2010 Nature Geoscience study: Oceans are acidifying 10 times faster today than 55 million years ago when a mass extinction of marine species occurred.” And we’ve known those impacts might last a long, long time — see 2009 Nature Geoscience study concludes ocean dead zones “devoid of fish and seafood” are poised to expand and “remain for thousands of years.”But until now, conventional wisdom has been that big ocean impacts might not be seen until the second half of the century. This new research in Nature suggests we may have much less time to act than we thought if we want to save marine life — and ourselves. The study concludes:In the oceans, ubiquitous microscopic phototrophs phytoplankton account for approximately half the production of organic matter on Earth. Analyses of satellite-derived phytoplankton concentration available since 1979 have suggested decadal-scale fluctuations linked to climate forcing, but the length of this record is insufficient to resolve longer-term trends. Here we combine available ocean transparency measurements and in situ chlorophyll observations to estimate the time dependence of phytoplankton biomass at local, regional and global scales since 1899. We observe declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year. Our analyses further reveal interannual to decadal phytoplankton fluctuations superimposed on long-term trends. These fluctuations are strongly correlated with basin-scale climate indices, whereas long-term declining trends are related to increasing sea surface temperatures.
