An individual-based model for evaluating post-exposure effects of UV-B radiation on zooplankton reproduction

Abstract

Solar ultraviolet (UV) radiation, and UV-B (280-320 nm) in particular, has been shown to be partially responsible for adverse effects on zooplankton throughout the world, from damaged DNA to altered population dynamics. To cope with these effects, copepods have developed several protective systems, including avoiding extended and intense periods of exposure. How much UV-B exposure a cohort of thousands of spawners can withstand remains unknown. To evaluate the post-exposure effects of UV-B radiation on reproduction in egg carrying copepods, we developed an individual-based model (IBM) that integrates in vivo data. We calibrated the IBM for a small cyclopoid copepod species, Paracyclopina nana, which is a biological model used in both ecotoxicology and aquaculture. Our findings improve our understanding of the species' response to UV-B radiation. Significant radiative effects include decreased reproductive success (at >= 0.7 kJ.m(-2)) and offspring production (at 0.6 >= kJ.m(-2)). The model predicted fewer than 500 females from an original cohort of 1000 would survive for five days after exposure to 1 kJ/m(2), and 50% offspring suppression eight days after exposure to 1 kJ.m(-2). This integrative model highlighted the importance of female longevity in maintaining a viable population at doses below 2 kJ.m(-2) and that of hatching success for radiation levels exceeding 2 kJ.m(-2). P. nana appeared to be a sensitive species at 25 degrees C but improvements in the model, such as incorporation of temperature variation effects and recovery mechanisms, should provide better estimates of the species' sensitivity to UV-B.