Effects of solar UV radiation on diatom assemblages of the Mediterranean

Three UV treatments (PAR; PAR + UVA; PAR + UVA + UVB) were performed by placing different W-absorbing filters over communities developing on ceramic tiles in a natural marine habitat near Korinthos, Greece, The experiment was repeated at three depths (0.5 m, 1 m, 1.5 m) below the surface of the sea, Differences in community structure due to UV radiation exposure were more pronounced during the early stages of community development. After the first 3 weeks of growth, the productivity of the PAR + UVA + UVB treatment was significantly lower than the PAR + UVA but not than the PAR treatment, This difference did not persist thereafter, At 5 weeks of growth, the productivity at 0.5 m was significantly lower that at 1.0 m, No other significant differences were observed. The findings of the present study suggest that periphytic communities occurring at the upper layers of the euphotic zone may be capable of adjusting to changes in environmental stresses such as by increased solar UVB irradiance.