Dissertation Research: Evaluating changes in food web linkages and mercury bioaccumulation by top predators in response to the removal of an introduced predator

The proposed research will investigate the effects of non-native piscivore removal in an Adirondack lake similar to many north temperate lakes. Smallmouth bass were introduced into the study Adirondack lake more than 50 years ago and subsequently reduced the abundance of native prey fish and altered the food web structure within the lake. An intensive smallmouth bass removal effort was implemented in 2000, resulting in increased native prey fish abundance and food web changes measured by stable isotope shifts. Mercury bioaccumulation in top predators have also been altered by the removal of non-native smallmouth bass.

This ongoing large-scale piscivore removal effort provides an opportunity to evaluate and quantify important ecosystem characteristics including community composition, food web and mercury bioaccumulation changes associated with the manipulation. The main objectives are to 1) quantify the changes in lake fish communities, food web linkages and mercury bioaccumulation in response to the removal of a non-native piscivore, 2) evaluate the processes responsible for these changes in these lake ecosystems and 3) evaluate piscivore removal as a management tool to restore lake ecosystems. Limited information is available regarding the effects of large-scale apex predator manipulations in north temperate aquatic systems similar to the proposed study lakes, which are common and provide abundant recreational angling opportunities throughout North America. Results from this study will provide an improved ability to: (1) use stable isotopes as a metric for lake fish community restoration, (2) understand processes responsible for variable accumulation of mercury in popular sport fish, (3) and implement management approaches to restore native fish communities impacted by dominant non-native species. Of particular interest is the positive impact of smallmouth bass removal on the New York State-designated endangered round whitefish, which is present in the study lake.

Funding has recently been obtained for the following project through the Keickhefer Adirondack Fellowship:

Modeling mercury bioaccumulation in sport-fish within an Adirondack watershed

Mercury contamination in fish is a serious human health issue in the northeastern United States and throughout the world. Factors influencing the bioaccumulation of mercury have been evaluated in many systems. Both biological and watershed characteristics affecting mercury levels in organisms have been examined, but these relationships can be highly variable across regions and species. Mercury contamination in fish is almost entirely in the form of methylmercury. The Adirondack region of New York State is prone to high levels of acid deposition, and because mercury methylation increases as pH decreases, methylmercury in the biota of many aquatic systems in the region is particularly high. This research will evaluate the relative influence of biological factors (e.g. length and weight) and watershed characteristics (e.g. pH and watershed area) on mercury bioaccumulation in smallmouth bass (Micropterus dolomieui) and lake trout (Salvelinus namaycush), popular sport and food fish within the Adirondacks. The work is unique in that it will occur across an interconnected system of Adirondack lakes and will assess factors affecting fish mercury levels both directly and indirectly. The overall objective of this study is to develop a model that integrates the significant biological and watershed level parameters to predict mercury concentrations in these species. The proposed study will also provide data that will be useful for improving consumption advisories for a fish species of concern in the Adirondacks.

Funding for the first two years of my dissertation research was provided by the New York Sea Grant Program:

Investigating thiaminase levels in clupeid fishes in tank and pond experiments using a newly developed thiaminase assay

My dissertation research has focused on evaluating environment and stressors on thiaminase expression in alewives and gizzard shad to expand on what is currently known about thiamine deficiency complex and associated reproductive failure in Great Lakes, Finger Lakes and European salmonine fishes. In collaboration with scientists at Cornell University and the USGS, a new thiaminase assay that is more sensitive and affordable than the previous assay has been developed and is being calibrated. This innovation will allow us investigate new ideas relating clupeids, thiaminolytic bacteria and environmental and other stressors to thiaminase expression.