UV-B dose/dose-rate responses of seasonally abundant copepods of Puget Sound

Summary

Refinements in modeling stratospheric processes and recent observational data have generated estimates of moderate future reductions in total global ozone. Nevertheless, considerable uncertainty and concern remain about whether or not the resulting increases in incident solar UV-B could increase the risk of harmful biological effects. The UV-B dose/dose-rate thresholds for five species of copepods collected at the surface in Puget Sound were determined and compared to previously studied zooplankton groups. Generally, species appearing later in the spring and summer were less UV-B sensitive. The UV-B daily-dose and dose-rate thresholds for the five species of copepods, while apparently less than present median incident levels, range from above to below estimated present and future subsurface (1 m) UV-B levels. A separate experiment with a relatively large copepod, Calanus pacificus, in which above and below threshold UV-B dose-rates were administered with various levels of photoreactivating light(UV-A and visible light), indicated the presence of photorepair and its full activation at relatively low intensity. To improve estimates of the extent to which present and predicted UV-B levels affect local populations of copepods and zooplankton, it is essential to more fully understant the natural conditions or processes which influence the composition and intensity of the UV irradiation these animals receive.