UV damage and photoreactivation potentials of larval shrimp, Pandalus platyceros, and adult euphausiids, Thysanoessa raschii.

Previously reported thresholds for UV-B dose and dose-rate were determined under artificial light regimes using more than an order of magnitude less visible light than found naturally. Near-UV and/or visible light is needed for photoreactivation, and the accuracy of earlier findings may have been influenced by less than maximum photorepair in the laboratory. Experiments with shrimp larvae and adult euphausiids, comparing survival at various UV-B doses and dose-rates combined with different levels of near-UV and visible irradiance, suggest that photorepair occurs in these organisms. Further, this apparent photorepair reaches maximum levels at relatively low visible light intensities.Previously reported tolerance limits for shrimp larvae and adult euphausiids were confirmed (in particular, the relationship between dose/dose-rate safe and lethal limits in shrimp). Also, the earlier experimental design did not appear to have affected these limits since additional near-UV and visible light did not substantially alter the results.In experiments using a 44-1 plastic cylinder (140-cm water depth), adult euphausiids successfully avoided moderate UV-B combined with visible light, but were attracted to and ultimately killed by higher levels of UV-B combined with low visible light. The apparent inability of euphausiids to directly detect harmful levels of UV-B irradiance would become an important factor in a new solar spectral distribution caused by ozone depletion.