9525803 Franks This project will investigate how spatial and temporal variability in physical-biological features affects the development, condition and survival of Antarctic krill larvae (Euphausia superba). It is believed that adult spawning behavior and regional differences in primary productivity and temperature are significant forces controlling krill mortality, population demography and recruitment. Using a modified stage-structured larval population model, the effects of spawning behavior and variations in stage durations and mortalities on demography and recruitment will be examined. The model results will be compared with observed larval distributions to determine which processes best account for the observed population structures. Using a detailed metabolic model with stage structure and realistic external forcing, we will determine how much of the variability in stage durations and mortalities can be explained by the effects of food availability and temperature. Larval lipid metabolism will be incorporated into the model for elucidating the influences of physical and biological variability on larval krill condition. Models will integrate the effects of multiple parameters and will intimately coupled to field observations and laboratory experiments. This study will provided a valuable contribution to the understanding of interactions between marine populations and physical processes in the Southern Ocean ecosystem. The results from this study will be applicable to concurrent research investigating the physical-biological interactions affecting Euphausia superba in the Southern Ocean, and Euphausia pacifica in the California current. The ultimate intent is to quantify the impact of physical-biological patchiness associated with physical features and phenomena on larval condition, demography and recruitment in euphausiid populations. Understanding species' responses to physical perturbations will elucidate how environments have evolutionarily constrained life- history patterns to maximize survival in inherently patchy and variable systems. Through this understanding, this study will provide insights into the potential effects of climatic change on euphausiid populations and their ecosystems.
