Effects of UV-B irradiated algae on zooplankton grazing

H.J. de Lange, M.F.L.L.W. Lürling

Research output: Contribution to journalArticleAcademicpeer-review

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We tested the effects of UV-B stressed algae on grazing rates of zooplankton. Four algal species ( Chlamydomonas reinhardtii, Cryptomonas sp., Scenedesmus obliquus and Microcystis aeruginosa) were used as food and fed to three zooplankton species ( Daphnia galeata, Bosmina longirostris and Brachionus calyciflorus), representing different taxonomic groups. The phytoplankton species were cultured under PAR conditions, and under PAR supplemented with UV-B radiation at two intensities (0.3 W m(-2) and 0.7 W m(-2), 6 hours per day). Ingestion and incorporation experiments were performed at two food levels (0.1 and 1.0 mg C l(-1)) using radiotracer techniques. The effect of food concentration on ingestion and incorporation rate was significant for all three zooplankton species, but the effect of UV-B radiation was more complex. The reactions of the zooplankton species to UV-B stressed algae were different. UV-B stressed algae did not affect Daphnia grazing rates. For Bosmina the rates increased when feeding on UV-B stressed Microcystis and decreased when feeding on UV-B stressed Chlamydomonas, compared with non-stressed algae. Brachionus grazing rates were increased when feeding on UV-B stressed Cryptomonas and UV-B stressed Scenedesmus, and decreased when feeding on UV-B stressed Microcystis, compared with non-stressed algae. These results suggest that on a short time scale UV-B radiation may result in increased grazing rates of zooplankton, but also in decreased grazing rates. Long term effects of UV-B radiation on phytoplankton and zooplankton communities are therefore difficult to predict.
Original languageEnglish
Pages (from-to)133-144
Publication statusPublished - 2003


  • fresh-water zooplankton
  • life-history traits
  • ultraviolet-radiation
  • daphnia-pulex
  • particle-size
  • food quality
  • in-situ
  • phytoplankton
  • responses
  • survival


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