Benthic-Pelagic Links in Lakes: Effects of Whole-Lake Fertilization and Fish Biomanipulations on the Contribution of Benthic Algae to Whole-Lake Primary Production.

This project is being conducted by graduate student Yvonne Vadebonceour, under the direction of advisor David Lodge, Ph.D., in the Department of Biological Sciences, 222 Galvin Life Sciences, University of Notre Dame

Two of the most common anthropogenic stresses on lakes are inorganic nutrient fertilization (especially nitrogen and phosphorus) and planned or unplanned alteration of fish species composition. Because nuisance phytoplankton blooms are the most obvious effects of fertilization little attention has been paid to other primary producers, especially benthic algae. In five lakes in upper peninsula of Michigan, the effects of whole-lake fertilization and fish manipulations on on benthic algal production are being examined.

Despite the historical limnological focus on phytoplankton and its response to anthropogenic stresses, prior to inorganic nutrient fertilization benthic algae contributed more than 70% of whole-lake primary production. The relative contribution of benthic algae declined with fertilization because the benthic algae did not increase with fertilization whereas phytoplankton increased dramatically. The role of benthic algae in both benthic and pelagic food webs is being examined through the use of stable isotope analysis of benthic algae, and primary and secondary consumers. Because benthic algae contribute so much to whole lake primary production, it is likely that benthic algae are energetically important to lake ecosystem function. This may be especially true for the maintainance of fish populations.