IMPACT OF ENHANCED SIMULATED SOLAR ULTRAVIOLET RADIATION UPON A MARINE COMMUNITY

Abstract—There is evidence to indicate that an increased exposure to solar radiation in the UV-B region (specifically, 290–320 nm) may occur as a result of anthropogenic degradation of stratospheric ozone. The fact that present levels of solar UV radiation can detrimentally affect marine organisms led to experiments to quantify the impact of increased UV radiation upon a marine community. Two 720–l seawater chambers (continuous flow-through design) were exposed to simulated solar UV radiation. Fluorescent sunlamps filtered by a 290 nm cutoff filter (a 0.13 mm thickness of cellulose triacetate film) were used as the radiation source. Utilization of three different weighting factors for the spectral irradiances at the surface of the chambers yielded differences of 18%, 35% and 40% in biologically effective fluence rate between the two chambers. Analysis of attached forms of algae at various depths demonstrated that a surface exposure of 1.4W/m² in the 290–315nm waveband as contrasted with the chamber receiving a surface exposure of 1.0W/m² resulted in depressed Chl a concentrations, reduced biomass, increased autotrophic indices, and decreased community diversity. These results indicate a potential for adverse effects of increased solar UV-8 radiation: decreased community diversity, community structure shifts, and decreased productivity.     

IMPACT OF UV-B RADIATION UPON ESTUARINE MICROCOSMS

Abstract— Twelve flow-through estuarine microcosms were exposed daily to four different levels of UV-B radiation (290–320. nm)(1.57 ± 10², 6.43 ± 10³, 6.86 ± 10³ and 7.61 ± 10³ J·m_-2d⁻¹) in addition to a natural level of visible solar radiation (380-800. nm). The parameters studied over a four week period were phytoplankton community composition, plankton biomass (ash-free dry weight), chlorophyll a concentration and primary productivity (radiocarbon uptake). With increased exposure to UV-B radiation there was an obvious alteration of the community composition. Daily exposure to enhanced levels of UV-B radiation also depressed the biomass, the chlorophyll a concentration and the radiocarbon uptake of samples from the ecosystems.     

SENSITIVITY OF MARINE PHYTOPLANKTON TO UV-B RADIATION: IMPACT UPON A MODEL ECOSYSTEM

Abstract Human activities may cause a 16% reduction of stratospheric ozone. The concomitant increase in solar UV-B radiation reaching the surface of the earth could detrimentally affect the phytoplankton that form the base of the food web in oceanic and estuarine ecosystems. In the current study acute exposure of seven species of marine phytoplankton to UV–B radiation depressed the radiocarbon estimate of primary production. A model of a marine ecosystem was constructed based on the differential sensitivities of the seven species of phytoplankton. Increasing the UV–B exposure within the model from 100 Eff_DNAJ/m²/day to 150 Eff_DNAJ/m²/day significantly altered the community composition of the ecosystem. In nature, alteration of the phytoplanktonic community structure could result in a significant impact upon successional patterns and primary producer–consumer trophodynamics.     

DISTORTIONS IN AMPHIBIAN DEVELOPMENT INDUCED BY ULTRAVIOLET-B ENHANCEMENT (290–315 NM) OF A SIMULATED SOLAR SPECTRUM

Abstract— Effects of increased intensity of UV-B radiation (290–315nm) on the systemic development and viability of boreal toad tadpoles were studied. When compared with animals exposed to UV-B deficient radiation of similar irradiance, tadpoles exposed to UV-B enhanced radiation displayed (1) abnormal development of the presumptive cornea, (2) areas of hyperplasia in the integument, (3) an anomalous, concave curvature of the spine, and (4) increased mortality. Daily exposure to photoreactivating radiation (> 315nm) following UV-B insult mitigated the potentially lethal damage to the tadpole population.