Modeling the growth, biomass, and of Cladophora glomerata tissue phosphorus concentration in eastern Lake Erie: Model description and field testing

Cladophora glomerata is a filamentous alga that currently forms extensive blooms in nearshore areas of Lake Ontario, eastern Lake Erie, Lake Michigan, and isolated locations in Lake Huron. During the late 1970s an extensive effort was put forward to model Cladophora growth and biomass accrual based on several highly dynamic ecological variables including: Photosynthetically active radiation (PAR), soluble reactive phosphorus (SRP), water temperature, and carrying capacity (Canale and Auer 1982a). The original Canale and Auer model was developed and validated in proximity to a sewage treatment outfall in Lake Huron and predicted Cladophora growth and biomass over a range of SRP concentrations, at shallow depths (0-3 m), with reasonable accuracy. We present a revised version of the Canale and Auer model, which we refer to as the Cladophora Growth Model (CGM). The CGM expands its utility, of the Canale and Auer model to greater depths and to areas of non-point source P loading while reducing the quantity of input data required. The CGM was incorporated into a computer simulation model using Stella modeling software, and is available from the corresponding author of this manuscript. The CGM was tested over a single growing season at five sites, and three depths (2, 5, 10 m), that represented a wide geographical distribution and expected range in ecological conditions in eastern Lake Erie. The CGM predicted growth, biomass, and tissue phosphorus concentrations with reasonable accuracy. The revised model is useful for: 1) Predicting Cladophora growth, biomass, and tissue phosphorus concentrations under non-point source P loading with no depth restrictions; 2) providing estimates of the timing and magnitude of the midsummer sloughing phenomenon; 3) determining the contribution of Dreissena invasion to the resurgence of Cladophora in eastern Lake Erie; and 4) developing Management strategies for Cladophora abatement.