Ecological Studies and Mathematical Modeling of Cladophora in Lake Huron: 1. Program Description and Field Monitoring of Growth Dynamics

Abstract

A 3-year program was conducted to examine the ecology of Cladophora glomerata and to develop a mathematical model useful in evaluating various management strategies for the control of this nuisance alga. This manuscript provides a detailed description of the field program and study site in support of subsequent papers dealing with the results of field monitoring, autecological studies, calibration and verification of the model, and the impact of a demonstration phosphorus removal program on Cladophora growth. A municipal wastewater treatment plant discharge at Harbor Beach, Michigan, on Lake Huron has resulted in severe nuisance conditions associated with the presence of Cladophora. An intensive field monitoring program was established at the site to record weather conditions daily, and levels of dissolved and stored phosphorus and standing crop of Cladophora on a weekly basis. The distribution of Cladophora was shown to be essentially symmetrical about the nutrient source. Seasonal variation in biomass followed a pattern of early spring growth, stabilization, and midsummer senescence. The high degree of spatial and temporal heterogeneity in the nearshore environment was clearly evident from the results of the monitoring program. Wind direction and velocity importantly affect dissolved phosphorus distribution. Internal phosphorus levels reflect long term trends in wind and current regimes. The growth of Cladophora is importantly influenced by internal phosphorus levels while the loss of algal material through sloughing is closely correlated with wind-storm events. The observations of nearshore dynamics point to the need for high sampling frequency in such systems.