**The title, authors, and abstract for this completion report are provided below. For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**

 

 

Bioaccumulation of microcystin in the Bay of Quinte food-web

 

Stephanie Guildford2 and John Berry3

 

2 Department of Biology and Large Lakes Observatory

University Minnesota Duluth

2205 East 5th St. Duluth, MN 55812

 

 

3 Department of Chemistry and Biochemistry

Florida International University, Miami, FL

 

 

June 2011

 

ABSTRACT:

Microcystin, a potent hepatotoxin produced by cyanobacteria, has become an increasing concern in the North American Great Lakes and many studies have been conducted to determine whether the increase in microcystin is due to changing environmental variables such as increases in nutrient loading to the lakes, increased water temperatures due to climate warming or in response to selective filtration by the exotic dreissenid mussels. Studies have focused primarily on one or two North American Great Lakes and some inland lakes. Environmental causes remain elusive. In this study of tropical (Lakes Victoria, Albert, and Edward) as well as temperate Great Lakes (Erie and Ontario) and several smaller temperate and tropical lakes which span a broad range of trophic status from mesotrophic to hypereutrophic, significant positive correlations were observed between total phosphorus (TP), chlorophyll a and microcystin in water. A similar trend was also observed within just the North American Great Lakes Erie (Maumee Bay) and Ontario (Bay of Quinte) and the smaller inland lakes in Ontario, but the relationships were not nearly as strong because the range of these three variables was not as large as when the more eutrophic African Lakes were included. In the North American lakes, microcystin in water rarely exceeded the WHO recommended guideline for drinking water (1.0 g L-1) however this concentration was consistently exceeded in all but one of the seven tropical study lakes with four of the lakes having mean concentrations > 6 g L-1. Microcystin in fish was measured in the study lakes and concentrations varied widely depending on species and fish size. Concentrations in some fish species exceeded the WHO recommended total daily intake (TDI) of 24 g kg-1 wet weight in not only most of the tropical lakes but also in Maumee Bay and Bay of Quinte. Several fish species with high microcystin concentrations were sampled from lakes where microcystin concentrations in water did not exceed the WHO recommended limit supporting the hypothesis that some fish species do bioaccumulate microcystin and thus can be a vector for human exposure even in lakes with acceptable microcystin concentrations in water. This study examining concentrations of microcystin in both water and in many species of fish across a broad range of lakes and trophic conditions highlights the combined potential risk to consumers from both water and fish. The exposure due to water and fish combined exceeded the WHO recommended total daily intake for all lakes except Lake Albert, Uganda. The study demonstrates that microcystin in water is consistently best predicted by total phosphorus.