Depletion of ozone in the stratosphere increases biologically damaging ultraviolet-B radiation (UVBR) at the Earth’s surface, and there is overwhelming evidence that UVBR damages marine organisms and penetrates to biologically significant depths in the ocean.
This damage is likely to reduce the capacity of Antarctic waters to act as a sink for atmospheric carbon dioxide (CO2) and exacerbate global climate change due to the greenhouse effect.
The research by scientists from the Australian Antarctic Division (AAD) and Southern Cross University has been outlined in a poster presentation at the 2004 Australian Marine Sciences Association Conference in Hobart.
Dr Sharman Stone, Parliamentary Secretary with responsibility for the Australian Antarctic Division said this research demonstrated the importance the Australian Government places on its Antarctic science program in advancing our understanding of how global processes arise, their interaction with the natural environment and their likely consequences.
AAD marine biologist Dr Andrew Davidson said that increased UVBR had a damaging effect on microbes such as phytoplankton.
“Phytoplankton proliferates around Antarctic coastal waters during spring and summer, the time during which UVBR light is increased by ozone depletion. These single-celled marine plants mediate global climate: absorbing CO2 that is responsible for global warming and, releasing compounds that aid the formation of clouds and increase reflectance of the sun’s rays.”
“Phytoplankton is the base of the food web and support the wealth of marine life for which Antarctica is renowned. Most studies have concentrated on the effect of UVBR on phytoplankton, but phytoplankton does not exist in isolation. Other microbes — the protozoa, bacteria and viruses — can also be directly damaged or killed by solar UVBR.”
Most of us visualise Antarctic life as being penguins, seabirds, seals and whales. However, marine microbes comprise some 95% of the living matter in the Southern Ocean and they consume most of the energy trapped by phytoplankton.
“Any UVB-induced impact at one level can alter the entire community. To understand the effect of UVBR, we need to consider both the effects on each of the species and those on the whole community,” Dr Davidson said.
“Results indicate that exposure to UVBR can change the marine microbial community, thereby affecting the abundance, size structure, palatability and nutritional quality of food within the food web.
“These changes are likely to enhance global warming by reducing both the uptake and storage of carbon in the ocean and release of cloud-promoting substances to the atmosphere. Though the effects of UVBR on natural microbial communities are often subtle, the ramifications may be far-reaching,” he said.