Paul E. Sager

Coupling ecosystem science with management: A Great Lakes perspective from Green Bay, Lake Michigan, USA

Continued resource degradation in various areas of the Great Lakes has led to doubts of the adequacy of conventional science and management approaches. The need for a more holistic approach, identified as an ecosystem approach, appears now to be more widely accepted although progress with implementation is slow. We argue here that ecosystem science is an integral part of an ecosystem approach and is a prerequisite to effective management planning.One of the problems of implementing an ecosystem approach is forging the link between ecosystem based research and management. For Green Bay, Wisconsin, USA, certain structural and functional qualities of the ecosystem have been used to define operational guides and to formulate management objectives. These objectives are being utilized in the development of a remedial action plan for Green Bay.

Modelling phosphorus transfer rates in lake water

Abstract A modification of Leans (1973 a,b ) four-compartment model of the transfer of phosphorus between soluble and particulate forms in the epilimnion of lakes is necessary to make the model consistent with certain observed transfer curves. By splitting the particulate compartment into two distinct fractions and incorporating appropriate transfer coefficients, differential rates of exchange with the particulate compartment can be simulated. At least two different rates of exchange with the particulate compartment appear to be necessary to make the model consistent with experimentally observed, diphasic phosphorus transfer curves.

Structure and Ordination of Epiphytic Invertebrate Communities of Four Coastal Wetlands in Green Bay, Lake Michigan

ABSTRACT Epiphytic macroinvertebrate communities of four coastal wetlands of Green Bay, Lake Michigan were compared by taxonomic composition, feeding group composition, and environmental influences using Bray-Curtis ordination. Ordination scores from the most sheltered oligotrophic site, Portage Marsh, were distinct from the eutrophic, exposed sites located in middle and lower Green Bay—Seagull Bar, Little Tail Point, and Dead Horse Bay. Epiphyton chlorophyll a, phytoplankton chlorophyll a, and specific conductance strongly correlated to the ordination axes, indicating the trophic gradient within Green Bay was a primary environmental influence. The feeding group compositions at the sites were consistent with the type and abundance of food available. Portage Marsh is a scraper-shredder system, with macroinvertebrates feeding mainly on epiphyton and coarse particulate detritus. Dead Horse Bay and Little Tail Point are collector systems, sustained by phytoplankton and fine particulate organic matter. Seagull Bar is intermediate in trophic position along the ordination axes, but more closely resembles the latter two sites. The type and abundance of food resources available to these invertebrate communities are influenced by wave exposure, light attenuation, nutrient levels, and algae levels of the littoral and pelagial waters. Macroinvertebrate communities were sensitive to shifts in food resources, which generated shifts in trophic structure.