Ecology and Restoration Potential of the Manchac Wetlands:
Effects of Contaminants upon Sunfish

A. Cheek and B. Henry

Project Overview

The activities of Louisiana's oil and gas refining industry may result in waterways that are laden with bottom sediments contaminated with high levels of polyaromatic hydrocarbons (PACs) and heavy metals, such as zinc, cadmium, and lead. These chemicals can cause the disruption of hormonal pathways in aquatic organisms, a phenomenon known as endocrine disruption. The sunfish, Lepomis spp, a common species of fish in the Lake Pontchartrain Basin, was chosen as the animal model to investigate the physiological and ecological impact of exposure to polyaromatic hydrocarbons and heavy metals. This study was designed to compare the reproductive cycles and juvenile recruitment of bluegill sunfish that spawn in an uncontaminated bayou in the Maurepas wetlands, Stinking Bayou, to sunfish that spawn in a hydrocarbon contaminated bayou in the LaBranche wetlands, Bayou Trepagnier. It was determined that while female sunfish move from bayou to bayou, male sunfish remain in the same bottom areas and, therefore, are exposed to contaminants for longer periods of time.

Male sunfish in the contaminated Bayou Trepagnier tend to have lower testosterone levels and higher estradiol (related to estrogen, the common female hormone) levels than males from the relatively pristine Stinking Bayou. There are more larval fish and a slightly greater richness of species (number of fish species) in Stinking Bayou. It is hypothesized that an alteration of normal processes, such as courtship behavior and spermatogenesis (the creation of sperm) may occur among affected sunfish.