 Populations of Antarctic phytoplankton have dropped significantly due to global warming, threatening the entire chain of ocean life, according to a study conducted by researchers from Rutgers University and published in the journal Science . Phytoplankton are microscopic plants that form the bottom of the oceanic food chain; they are fed upon by krill, which are eaten by whales and small fish. Small fish are then eaten by larger animals all the way up the chain to Adelie penguins and other macrofauna. Because phytoplankton, like other plants, produce chlorophyll in order to photosynthesize energy from sunlight, researchers used measures of chlorophyll off the coast of the Antarctic Peninsula to estimate levels of the microorganisms. They then compared these with satellite data over the last 30 years to examine the effects of global warming on plankton populations. The Antarctic Peninsula juts out from the continent toward South America. The rate of winter warming on the peninsula is higher than anywhere else on the planet. The researchers found that overall populations of phytoplankton off the west coast of the peninsula have dropped by 12 percent over the last 30 years. Looking more specifically at regional changes, the researchers were able to see that plankton populations have actually increased in the south, but have decreased by a greater amount in the north. In the south, decreasing cloud cover due to changing climate patterns has increased the sunlight available for the phytoplankton . 'You have more open water and so you have light penetration, so the phytoplankton is happy in the south,' researcher Martin Montes-Hugo said, In the north, however, greater cloud cover and increasing winds are reducing sunlight and driving plankton deeper underwater. 'This makes phytoplankton mad,' Montes-Hugo said. 'It's not good for phytoplankton because you have less light .' In addition to forming the base of the food chain, phytoplankton also absorb large amounts of carbon dioxide from the atmosphere, and emit large quantities of oxygen. Lower levels of plankton means more carbon dioxide in the atmosphere and faster global warming -- leading to still lower plankton populations and successively more warming. Sources for this story include: www.reuters.com . 