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Influence of Ozone-Related Increases in Ultraviolet Radiation on Antarctic Marine Organisms 1

Influence of Ozone-Related Increases in Ultraviolet Radiation on Antarctic Marine Organisms1

Deneb Karentz2,1 and Isidro Bosch2
1 Department of Biology, University of San Francisco, San Francisco, California 94117-1080
2 Department of Biology, State University of New York, Geneseo, New York 14454

Every spring for the past two decades, depletion of stratospheric ozone has caused increases in ultraviolet B radiation (UVB, 280–320 nm) reaching Antarctic terrestrial and aquatic habitats. Research efforts to evaluate the impact of this phenomenon have focused on phytoplankton under the assumption that ecosystem effects will most likely originate through reductions in primary productivity; however, phytoplankton do not represent the only significant component in ecosystem response to elevated UVB. Antarctic bacterioplankton are adversely affected by UVB exposure; and invertebrates and fish, particularly early developmental stages that reside in the plankton, are sensitive to UVB. There is little information available on UV responses of larger Antarctic marine animals (e.g., birds, seals and whales). Understanding the balance between direct biological damage and species-specific potentials for UV tolerance (protection and recovery) relative to trophic dynamics and biogeochemical cycling is a crucial factor in evaluating the overall impact of ozone depletion. After more than a decade of research, much information has been gathered about UV-photobiology in Antarctica; however, a definitive quantitative assessment of the effect of ozone depletion on the Antarctic ecosystem still eludes us.

It is only obvious that ozone depletion has not had a catastrophic effect in the Antarctic region. The long-term consequences of possible subtle shifts in species composition and trophic interactions are still uncertain.

The effects of ultraviolet-B radiation on freshwater ecosystems of the Arctic: Influence from stratospheric ozone depletion and climate change

Abstract: Depletion of stratospheric ozone, the principal atmospheric attenuator of ultraviolet-B (UVB) radiation, by man-made chemicals has raised scientific and public concern regarding the biological effects of increased UVB radiation on Earth. There is an increased awareness that existing levels of solar UV radiation have an important influence on biological and chemical processes in aquatic ecosystems. For aquatic organisms, numerous studies have shown direct detrimental effects of UVB radiation at each trophic level. Fortunately, many aquatic organisms also possess a range of photoprotective mechanisms against UV radiation toxicity. In addition to its direct impact, harmful effects of UVB radiation at a single-trophic level can cascade through the food web and indirectly affect organisms from other trophic levels. Because UV radiation photochemically reacts with humic substances and other photosensitive agents in the water, increases in solar UVB can also indirectly affect aquatic organisms through the production and (or) release of different photoproducts like biologically available nutrients and harmful reactive oxygen species.

Polar aquatic ecosystems have been of particular concern, since stratospheric ozone-related UVB increases have been the greatest in these regions. With the influences of climate warming and the possibility of future volcanic eruptions, ozone losses are expected to get worse in the Arctic stratosphere, and the ozone layer recovery may not follow the slow decline of industrial ozone-depleting compounds in the atmosphere.

Climate warming is also expected to bring important changes in underwater ultraviolet radiation (UVR) penetration in Arctic freshwaters that would be more significant to the aquatic biota than stratospheric ozone depletion.


Life and the Evolution of Earth's Atmosphere

James F. Kasting,1* Janet L. Siefert2

Harvesting light to produce energy and oxygen (photosynthesis) is the signature of all land plants. This ability was co-opted from a precocious and ancient form of life known as cyanobacteria. Today these bacteria, as well as microscopic algae, supply oxygen to the atmosphere and churn out fixed nitrogen in Earth's vast oceans. Microorganisms may also have played a major role in atmosphere evolution before the rise of oxygen. Under the more dim light of a young sun cooler than today's, certain groups of anaerobic bacteria may have been pumping out large amounts of methane, thereby keeping the early climate warm and inviting. [color=#990000]The evolution of Earth's atmosphere is linked tightly to the evolution of its biota.[/color]

The impact of enhanced ultraviolet-B radiation on litter quality and decomposition processes in Vaccinium leaves from the Subartic…