An Assessment of Mirex Concentrations along the Southern Shorelines of the Great Lakes, USA

Dennis A. Apeti,Gunnar G. Lauenstein

doi:10.3844/ajessp.2006.95.103

Abstract

Mirex is a persistent and toxic polychlorinated pesticide that has compromised environmental quality in the Great Lakes region since the 1960s. As a bioaccumulative and carcinogenic compound, mirex at its current levels in Lake Ontario is a concern because of the potential for trophic level transfer and biomagnification in top predators. As a part of the NOAA’s National Status and Trends Program (NS&T), zebra mussels and surficial sediments were surveyed throughout the Great Lakes since 1992 to monitor a broad suite of contaminants, including mirex. The non-parametric Wilcoxon test revealed that Lake Ontario consistently had the highest mirex concentrations (p < 0.0054) followed by Lake Erie while Lakes Huron and Michigan had the lowest concentrations. Current concentrations of mirex at Lake Ontario sites are at or above the NS&T benchmark of 85th percentile (2.33 ng g-1 dry weights) determined among all sites in the Great Lakes. The Spearman correlation statistic revealed an overall decreasing trend in tissue concentration, but this decline is only significant in Lake Ontario (p< 0.02) over the monitoring period 1992-2004. Photodegradation, volatilization, fishing and loss via the St Lawrence River are discussed as mechanisms resulting in the mirex decline.

Highlights

In 1986, the National Oceanic and Atmospheric Administration (NOAA) initiated nationwide coastal monitoring for a suite of organic and inorganic contaminants under the National Status and Trends (NS&T) Mussel Watch Project (MWP) using bivalve mollusks as sentinel organisms
The nonparametric Wilcoxon Signed-Ranks test shows an overall decrease of mirex concentration in mussel tissue in the Great Lakes since 1992 (Fig. 5 and 6)
A decreasing trend was observed in the Great Lakes overall, the patterns was driven by Lake Ontario where mirex concentrations have dramatically declined (p < 0.02)

Summary

Introduction

In 1986, the National Oceanic and Atmospheric Administration (NOAA) initiated nationwide coastal monitoring for a suite of organic and inorganic contaminants under the National Status and Trends (NS&T) Mussel Watch Project (MWP) using bivalve mollusks as sentinel organisms. A suite of more than 120 contaminants measured by the MWP[2] is quantified in the Great Lakes, including mirex. As a fully saturated organochlorine, mirex is strongly resistant to biodegradation and its lipophilic property (Log kow of 7.13) indicates a strong bioaccumulative capacity[4,5,6]. Top predators such as lake trout and piscivorous birds (ospreys and herring gulls) have been reported to contain high concentrations because mirex is biomagnified along the food chain[7].

Objectives

Methods

Results

Conclusion