Assessing the impacts of solar ultraviolet radiation on the early life stages of crustacean zooplankton and ichthyoplankton in Marine coastal systems

Over the past 10–15 years, solar ultraviolet B (UV-B, 290–320 nm) levels have increased significantly at mid-latitude areas of the Northern and Southern Hemispheres. These increases in UV-B are linked to reductions of stratospheric ozone. Although the variables that affect UV-B penetration into water columns are still under active investigation, there are typically strong correlations between dissolved organic carbon (DOC), chlorophylla (chla), and UV attenuation. This is particularly significant in the context of possible UV-B impacts on marine coastal systems, since DOC and chla are usually much more highly concentrated in these waters than in the open ocean. Observations indicate that the early life stages of crustacean zooplankton and ichthyoplankton present in the first meter of coastal water columns (like only a small percentage of the total population) are susceptible to UV-B radiation. Variability in cloud cover, water transparency (and the variables that affect it), and vertical distribution and displacement of organisms within the mixed layer have a greater effect on the flux of UV-B radiation to which plankton are exposed than will ozone layer depletion. Although exposure to UV-B can negatively affect planktonic organisms, such directs effects are likely minimal in coastal zones, and within the context of all the other environmental factors that produce the very high levels of mortality typically observed in their early life stages. Indirect effects (e.g., UV-B-induced reduction in the nutritional quality of the food base) have not as yet been adequately evaluated.