Cladophora Modeling in the Great Lakes

This study is the first step towards development of a nearshore ecosystem model that could be used to support management of nearshore areas with respect to water quality problems, in particular Cladophora. The specific goal is to couple a hydrodynamic and a Cladophora model, and apply and test the coupled model for a nearshore region in Lake Ontario, in connection with the Lake Ontario Nearshore Nutrient Study (LONNS). Through sensitivity analyses under shallow and deep water conditions and other comparisons of the Cladophora Growth Model (CGM) from Higgins and the Great Lakes Cladophora Model (GLCM) from Tomlinson et al., the GLCM was selected because it is simpler and more stable. Spatial resolutions of attached and sloughed Cladophora biomass on the Oak Orchard nested region of Lake Ontario were obtained by coupling the Princeton Ocean Model (POM) to GLCM. The results show that Cladophora was concentrated along a width of approximately 1 km off the coast (water depth 0-10 m) and the highest attached and sloughed biomass for each nested grid were both achieved on the 191st Julian day in year 2008. A particle tracking model (PTM) was later combined with these two models and was used to predict the sloughed biomass transport pattern (forward PTM) and simulate the potential source region of the sloughed biomass observed on the beach (backward PTM). Modeling results show that more than 50% of the sloughed Cladophora crashed on the nearest beach within 12 hours after sloughing and the potential source region of the sloughed Cladophora on the beach is the nearest nearshore region.