Freshwater Mussels

Freshwater mussels are the most endangered group of animals in the world. More than 70% of known species are considered rare or endangered. I am studying freshwater mussels to find why they are disappearing so rapidly and to use them as a model system to study the processes of population and species extinctions. We are studying a series of lakes in Iowa and Minnesota to determine the characteristics of aquatic ecosystems leading to the rapid disappearance of mussels. We have also analyzed rates of species loss at >100 sites in Iowa and studied the relationship of mussel declines to land use and water quality. We have observed huge mass die-offs of mussels and diagnosed the causes of mussel death. Other research in my lab has indicated that freshwater mussels are likely to be among the oldest living animals on earth, attaining ages of more than a century. Their advanced ages, slow population renewal, and complex life histories make them prone to over-exploitation. It seems unlikely that any rate of exploitation can be sustained by freshwater mussels since decreases in population density decrease reproductive output.




Aquatic Ecology, Biogeochemistry, Chemical Limnology, and Marine Ecology

Nutrients are well known to influence the primary production of aquatic systems, but the relative concentrations of nutrient elements (stoichiometry) can have a great impact on community structure and function. I have been working to determine how run-off from terrestrial systems and other nutrient sources influences the nutrient stoichiometry of freshwater systems and the sea. This biogeochemical research is of interest for two reasons: (1) this region is the source of a large fraction of the elements that become nutrients in the sea, and (2) we need to understand how linkages between watersheds and waterbodies influence ecosystem function in this highly impacted area. This research seeks a better understanding of nutrient/community interactions for use in ecosystem conservation and management.

Please refer to our Limnology Lab site ("Current Lake and Watershed Studies") for information on the following projects: 

Iowa Lakes Survey

Clear Lake Watershed Study   

Crystal Lake Watershed Study

Lake of Three Fires Watershed Study

Rock Creek Lake Watershed Study

Lake Rathbun Watershed Study


Sustainable Development of Natural Resource Organisms

 I believe that ecologists can develop theory that can be used in the rational and sustainable development of biological resources. I have been teaching a course that I developed on this subject since the early 1980s. Two axes of this research touch on the prediction of natural production rates in populations of aquatic and terrestrial animals and the analysis of extreme age and life history strategies as they impact the debate over compensatory vs. depensatory population dynamics.



Littoral Zone Limnology

One aspect of freshwater ecology that has long amazed me is that most aquatic ecologists work exclusively on the deep, open waters of lakes, whereas most of the aquatic production, recreational use and fish yield are centered on the shallow waters (i.e. the littoral zone). Work centers on the open waters because it is so much less messy to work in! I have been working for several years to develop good methods of sampling the plants and animals of the shallow waters of lakes, ponds and rivers, and am now beginning to apply them to research on interactions between fish, invertebrates and aquatic plants. For example, we are using stereo underwater video methods to measure and assess the use of the shallow waters by various fish species. We are able to measure fish with great accuracy, measure their swimming speed and spatial distributions. This research is yielding a new "window" on aquatic systems.