Stratospheric Ozone Depletion: Implications for Marine Ecosystems

As a result of stratospheric ozone depletion, UV-B radiation is likely to increase over the next few decades. In the sea, the amount of radiation reaching any given depth depends on the total amount reaching the sea surface (largely a function of latitude, season, time of day and cloudiness), the degree of sea-surface roughness (which determines the amount reflected back into space), and the scattering and absorption within the water column. In clear ocean water UV-B radiation is reduced to 1% of the surface level at a depth of about 28m while in productive coastal waters the 1% level may occur at only 1 or 2m (Baker and Smith, 1982). By contrast, visible light will be attenuated to the same 1% level at a depth of 100m in clear oceans, and 15m in more turbid coastal waters. Increased UV-B radiation has been shown to have a variety of deleterious effects on both individual marine organisms and simulated (mesocosm) marine ecosystems (Worrest, 1986). Models predict that tropical organisms, currently receiving the largest doses of UV radiation, will receive a small percentage increase, while boreal organisms, currently receiving much lower UV doses, will receive much larger percentage increases. Whether or not tropical or boreal organisms will be able to adapt to the predicted increases remains uncertain. This report will focus on possible effects on marine organisms of a 16% reduction in stratospheric ozone from pre-1970 levels and identify major uncertainties. The 16% case is representative of mid-latitude changes which may occur by 2060. (DBO)