Dr Eckman and collaborators will develop some general, quantitative models designed to assess the relative roles of transport, turbulent mixing and shear, larval development and larval behavior in producing spatial and temporal variability in rates of settlement of planktonic larvae of benthic invertebrates. The focus will be largely, but not exclusively, on unique problems faced by planktonic larvae of benthic existence. These investigators will begin by creating simple, steady, 1-dimensional models that should enable us to evaluate selected larval flux conditions at the boundary, and to assess the relative influence of many important scaling variables on settlement rate. Variables studied in 1-D models will include the scale and density of bottom roughness features, boundary shear velocity (including lift and drag forces exerted on larvae), turbulent mixing, larval swimming, substrate selectivity by larvae, and the degree of larval competence to settle. The development and evaluation of these models will include laboratory studies of larval behavior and settlement to ensure accuracy. The models will indicate which scaling variables must be incorporated, and which can reasonably be deleted, from more complex models that more closely mimic field situations. Dr. Eckman et al. will build and evaluate a series of more complex, ideal models, which have broader ecological relevance. These models will include time-dependent flows that account for wind-wave or tidal forcing, and 2-dimensional, steady flows that incorporate horizontal gradients in bottom roughness or depth. Thus, the research will incorporate physical dynamics, biological development and behavior into quantitative formulae. This work will generate predictions of variability in rates of larval settlement in space and time for several ecologically relevant situations. For each case, the models will indicate the relative sensitivity of larval settlement rates to a suite of potentially important hydrodynamic and biological process. The research proposed includes conceptual studies of simplification and predictability, and prototype investigations of biological processes in idealized flow fields - two categories of research targeted for support under GLOBEC's modelling program.
