Utilization of Parasite Community Structure as an Indicator of Environmental Pollution

W. Font

Project Overview

Environmental problems in West Lake Pontchartrain include petrochemical and heavy metal pollution of wetlands and bayous within the basin. Dr. William Font and his lab are embarking upon a project to see if fish parasites might indicate pollution levels.

As animals, such as fish, feel less healthy they become more susceptible to parasites. This sounds as though parasites should increase in polluted environments. This assumption, however, is not correct. This is because of a unique adaptation of the helminth parasites in this study: to mature, they must spend part of their life cycle in a snail, and the snails tend to decrease in number and diversity in the presence of pollution. Therefore, parasite richness (the number of different kinds of parasites) is expected to decrease in the polluted waterways.

Our objectives are:

• to document declines in parasite species richness and decreases in parasite prevalence and abundance in polluted sites and
• to determine the biological reasons for these decreases.

We will compare the parasite community structure of fishes in the families Poeciliidae and Cyprinodontidae at one polluted site, Bayou Trepagnier in St. Charles Parish, Louisiana with several similar but unpolluted bayous in the Lake Pontchartrain drainage.

A recent study indicated a decrease in pickiness of the parasites, which might indicate a decrease in host immunity. As the fish get sicker, the parasites become less choosy as to the species of fish they parasitize. Other ongoing studies are examining the intermediate snail hosts.

The studies underway are:

• Pollution Responses of Monogenea among Poeciliid and Cyprinodontid Fishes in the Lake Pontchartrain Basin
  

• Pollution Responses of Parasites with Indirect Life Cycles in Lake Pontchartrain Basin Mosquitofish
  

• Prevalence and Abundance of Selected Species of Trematode Parasites from Lake Pontchartrain Basin Fishes