Isotopic views of food web structure in the Florida Everglades

Introduction

Nearly one million acres of the Everglades are under a health advisory that discourages the human consumption of largemouth bass and several other fish because of high mercury contents. Food web structure (base of food web, number of trophic steps) plays a potentially critical role in determining the patterns of mercury contamination of the Everglades ecosystem. Methylmercury (MeHg) is present in low concentrations in water, yet after entering the base of the food web it biomagnifies to toxic concentrations in organisms that occupy higher trophic positions (like bass). One of the main research questions under investigation by a multi-agency task force in the Everglades is how MeHg bioaccumulates up the food chain in this complex aquatic ecosystem. Understanding variations in food web structure may help explain mercury patterns in the Everglades and ultimately lead to more effective restoration of Everglades ecosystems.