AME 19:269-278 (1999)  -  doi:10.3354/ame019269

UV radiation effects on microbenthos--a four month field experiment

Angela Wulff1,*, Claes Nilsson1, Kristina Sundbäck1, Sten-Åke Wängberg2 Svante Odmark1

1Department of Marine Botany and 2Department of Plant Physiology, Göteborg University, PO Box 461, 405 30 Göteborg, Sweden

ABSTRACT: A 4 mo field experiment, covering the period May to September, was carried out in a shallow microtidal sandy bay on the Swedish west coast. To test whether the ambient UV radiation (UVR) had any effect on a marine microbenthic community, screens of Plexiglas, Plexiglas + Mylar-D film and polycarbonate were used. This gave 3 different treatments: Ambient (PAR+UVAR+UVBR), NoUVB (PAR+UVAR) and NoUV (PAR) plus Control (areas without screens to test the 'frame effect'). The response of the community was studied on 2 occasions (June, September) by measuring primary productivity (14C), carbon allocation (14C) and bacterial productivity (3H-thymidine) (rate variables), as well as biomass and composition of microalgae and meiofauna, pigment composition (HPLC), content of mycosporine-like amino acids (MAA, HPLC) and composition of fatty acids (GC). The UVR maximum penetration depth (1%) in the sediment, measured by microsensors, was 800 μm for UVAR and 600 μm for UVB. No UVR effects were found for any structural variables but ostracodal biomass, which doubled when exposed to UVR compared with the UVR excluding treatments. Significant treatment effects were found for the rate variables primary productivity and carbon allocation. The effects on primary productivity and ostracods were observed in September only. All the treatment effects were found between exclusion of and exposure to UVR. Primary productivity increased in treatments shielded from UVR. For carbon allocation, significant effects on all fractions were found, however, with a partly different outcome in June and September. We conclude that the UVBR part of the spectrum exerted some stress on the microbenthic community, but this was almost exclusively found for rate variables in September, and that the ambient UVAR did not have any harmful effects. It is also concluded that the choice of time scales and experimental approach (laboratory vs field experiments) is crucial for the outcome and interpretation of UVBR experiments.

KEY WORDS: Microalgae · Production · Bacteria · Meiofauna · Carbon allocation · Pigments · Mycosporine-like amino acids · Sediment

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