Graduation date: 1990Anthropogenic releases of trace gases into the\ud atmosphere are causing a decrease in stratospheric ozone\ud concentrations and a subsequent increase in solar\ud ultraviolet-B (UV-B)(280-320 nm) radiation reaching the\ud earth's surface. The objective of this study was to\ud determine the acute effects of enhanced UV-B radiation on\ud the primary production of natural marine phytoplankton\ud assemblages sampled over a wide latitudinal gradient and\ud incubated under ambient levels of photosynthetically active\ud radiation (PAR). Samples were collected approximately every\ud 2 to 4° latitude in the southeast Pacific. Primary\ud production was measured using the carbon-14 light and dark\ud bottle technique. Fluorescent sunlamps were used to enhance\ud the dose of UV-B radiation above ambient. Samples were\ud maintained at ambient surface water temperature in a flow-through\ud incubation tank. Enhanced UV-B radiation caused a\ud significant mean decrease of 34% in surface water primary\ud production. Decreases in primary production increased with\ud and with increasing assimilation efficiencies. Results\ud indicate that predicted increases in ambient solar UV-B\ud radiation resulting from stratospheric ozone depletion could\ud result in mean annual decreases of near-surface oceanic\ud primary production of less than 1% near the equator to more\ud than 32% at high southern latitudes
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