¹Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, Columbus, Ohio 43210
²Department of City and Regional Planning, The Ohio State University, Columbus, Ohio 43210
³Great Lakes Laboratory for Fisheries and Aquatic Sciences, Department of Fisheries and Oceans,Burlington, Ontario L7R 4A6
⁴National Water Research Institute, Environment Canada, Burlington, Ontario L7R 4A6

*Corresponding author: culver.3@osu.edu

Summary

   In order to measure changes in ecosystem health in Lake Erie, we developed a biological water quality assessment tool. The Planktonic Index of Biotic Integrity (P-IBI) was developed using Lake Erie zooplankton and phytoplankton data from 1970 and 1996, validated with respect to total phosphorus and chlorophyll a concentrations, and applied to a number of years of Lake Erie plankton data. P-IBI candidate zooplankton metrics included an abundance ratio of calanoid copepods to cladocerans and cyclopoid copepods, percentage density of large Daphnia, rotifer composition, density of the calanoid copepod Limnocalanus macrurus, percentage biomass of the predatory invasive zooplankters Bythotrephes and Cercopagis, biomass of crustacean zooplankton/ biomass of phytoplankton, and biomass of crustacean zooplankton. Candidate phytoplankton metrics included a generic index of diatoms, abundance ratio of centric diatoms to pennate diatoms, biomass of inedible algae taxa, percentage biomass of bluegreen algae of the total phytoplankton biomass, percentage biomass of the potentially toxic Microcystis, Anabaena, and Aphanizomenon of total phytoplankton biomass, and biomass of edible algae taxa. Discriminant analysis was used to evaluate candidate metrics relative to Lake Erie degradation. Significant metrics for June included biomass of edible algae taxa, percentage Microcystis, Anabaena, and Aphanizomenon of total phytoplankton biomass, and an abundance ratio of calanoids to cladocerans and cyclopoids. The only significant metric for July was the density of Limnocalanus macrurus, while both the zooplankton abundance ratio and crustacean zooplankton biomass were significant metrics for August. The P-IBI showed an increase in water quality between 1970 and the mid-1990’s, with declining water quality in the late 1990’s and 2002.