Historical Reconstruction of Chemical Loadings and Ecosystem Effects in Delaware Bay Tidal Marshes

Introduction

Loadings of nutrients and contaminants have resulted in substantial impacts to estuarine systems such as eutrophication and high levels of lipophilic chemicals in finfish. Since the passage of the Clean Water Act and other legislation, loadings have been reduced and ecological health often improved. However, long-term monitoring is lacking and in many systems and ecological responses are not well quantified.

sediment core sampling

Because of their ability to adsorb trace metals and organic contaminants, fine-grained sediments trapped in tidal marshes represent a major repository for contaminants and ecosystem change. Sediment cores from these marshes provide an excellent means for documenting long-term (e.g., decadal scales) changes in land use, nutrient and contaminant loadings, and related ecological changes. Importantly, sediment chronologies derived from sediment cores help provide an understanding of whether or not source reduction programs (e.g., wastewater treatment, waste site remediation projects, non-point source controls) are successful, and under what time scale a river/estuarine-wide response can be detected. The response time is an important parameter in many water quality models (i.e., TMDL) when source reduction and load allocations will be determined.

Sediment cores were obtained from freshwater tidal and estuarine marshes in the Delaware Estuary to estimate historic loadings of chemical contaminants, nutrients and their potential ecosystem impacts. Chronologies were determined with 210Pb and 137Cs isotopes and sediment pollution records extending back through much of the past century. This work is a collaboration of the College of Marine and Earth Studies, University of Delaware, and the Patrick Center for Environmental Research of The Academy of Natural Sciences.

The objectives of this study are to address these questions:

  • Have nutrient and contaminant pollution controls been successful in the tidal Delaware River?
  • Have there been ecosystem level responses?
  • How will estuarine marshes respond to potential increases in sea level rise over time?
Download the EPA Star Final Report:
“Linking Impacts of Climate Change to Carbon and Phosphorus Dynamics Along a Salinity Gradient in Tidal Marshes”