Ozone Depletion, UVB harms Plankton, oceanic CO2 uptake lessened.

line drawing: krill

Krill &the Circle of Life

by Bruce Torrie

This year (1995), reports circulated that 10-15 % of the estimated 3.3 million grey kangaroos in Australia have been "blinded by a mysterious virus." Researchers suggest that this epidemic may be due to increased levels of ultraviolet B radiation (UVB) turning off the kangaroos immune system, leaving them prone to previously harmless viruses. In the spring of this year Associated Press reported that penguin chicks were "starving to death near one of Australia's bases in the Antarctic..... the penguins can't find enough krill: small shrimp like crustaceans they depend on for their food."

Last December, the Antarctic region saw the most profound depletion of atmospheric ozone ever: a hole with a 75% depletion stretching over an area larger than the entire North American continent. The thickness of ozone and the area affected under the hole fluctuated and moved with the weather, exposing a vast area of ocean to hitherto unprecedented levels of UVB.

Prior to human production and release of ozone depleting substances, the layer that protects life on Earth from harmful radiation was thickest at the poles. Scientists now think that this may be the reason for the great abundance of life present in the polar and sub polar oceans. New research shows that nano and pico plankton, extremely tiny organisms, are much more abundant than previously estimated. Now, plankton are believed to be 10 to 100 times more abundant in the polar and sub-polar regions than in the temperate and equatorial oceans. Accordingly, most of the world's biomass is living under the polar ozone holes, and is now being exposed to unprecedented levels of UV radiation.

This situation may accelerate global warming by affecting the complex oceanic food chain. Phytoplankton are tiny plants which float in the water column. Zooplankton are tiny animals which graze on the phytoplankton. These two organisms are critical to the oceanic food supply. In the Antarctic spring, as the ice recedes, tremendous blooms of plankton feed off carbon dioxide absorbed from the air by the oceans. By this process, vast amounts of CO2, an effective "greenhouse" gas, are removed by planktonic plants, thus helping to keep CO2 levels down in the atmosphere.

Recently published research indicates that plankton communities are dramatically affected by UVB, and some vital types of small plankton are the main food source for krill: the small shrimp-like plankton known as copepods, which often make up 70-90%of zooplancton.

The krill are vulnerable in several ways. According to David Lean, a senior research scientist with Environment Canada, "The little tiny ones were obliterated when exposed to UVB... in Antarctica the baby krill can only eat cells less than 20 micrometers in size. The baby krill give rise to big krill, and they are pivotal in the world Antarctic food chain. Without krill you don`t have whales; without krill you don't have seals. It is absolutely central to the whole Antarctic food chain."

Krill and other zooplankton are also disappearing from some areas of the temperate oceans. Reports show an 80% drop in the population of zooplanction off the coast of southern California.

So, we come full circle. UVB destroys small phytoplankton in the Antarctic ,contributing to global warming and a collapse in the polar and sub-polar oceanic food supply. Global warming causes a collapse of the zooplankton in the temperate and equatorial oceans, further contributing to the collapse of the oceanic food chain.

Reports of starving penguins and seals circulate, but provoke no popular concern or outrage. Meanwhile, the popular and scientific media offer little analysis or call for action.

In Berlin this Spring, at the World Climate Summit, the governments of the world blocked any progress on CO2 emission reductions.

Penguins are washing up on the beaches, and kangaroos are being shot as they blindly search for water. All these things - the oceans, the air we breathe, the food we eat and the sky above are interrelated. John Muir wrote almost a century ago that perhaps the universe would be incomplete without `Homo sapiens`, "but it would be incomplete without the smallest transmicroscopic creature that dwells beyond our conceitful eyes and knowledge". Only now as our ecologically blind society tears away the microscopic firmament of the web of life, are the top scientists proving the remarkable accuracy of Muir`s insight.

First appeared in the Lughnasadh 1995 issue of the U.S. 'Earth First! Journal'

Background info on the ozone layer, uv radiation, ozone depleting gases, ecological effects and a bit about phytoplankton are all in "The Ozone Layer" page. For more about krill, and a photo so you recognize one when you meet one, go to "Time to Krill".

For an up-to date encounter with krill afficianados, go to http://krill.rutgers.edu - cybermicroscope.

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