Projects

Use of stable isotope ratios to link wastewater sources to effects on shellfish and human health

End Date: 02/1/10

Abstract

Wastewater treatment plants (WTP) account for more than 30% of shellfish area closures in the U.S. and more than 70,000 ac in Mobile Bay. Shellfishing areas near WTPs are typically closed to fishing due to fecal coliform concentrations that may indicate human health risk. The reliability of this indicator, however, is uncertain. The FDA on Dauphin Island is testing an alternative indicator, male-specific bacteriophage (MSB), but lacks a method to definitely link their findings to wastewater sources. 

We propose to team with the U.S. FDA on Dauphin Island to determine whether WTP discharge affects growth and survival of shellfish or their safety for human consumption. To identify wastewater sources parallel with detection of microbial pathogens, we will transplant hatchery-reared juvenile and adult oysters (C. virginica) at locations, varying in proximity from the WTP on McDuffie Island in Mobile Bay (parallel to existing FDA sampling sites). We will combine FDA measurements of a highly reliable enteric pathogen proxy (MSB) and the traditional fecal coliform test with measurements of a natural tracer of anthropogenic wastewater sources (N stable isotopes). To determine corresponding effects on shellfish and their habitat, we will compare measurements of potential wastewater-driven changes on shellfish habitat (DO) and food supply (nutrient and chl a concentrations) and measurements of variation in shellfish growth and survival through time. 

Based on the results of year one, in year two, we will choose sampling locations to best capture variation in dilution due to hydrology and level of WTP processing. Our primary objective is to collect data that will enhance coastal economies by helping to maintain and restore local shellfish populations, increase the area of land available for shellfishing, inform efficient determinations of market-safe shellfish, and reduce the risk of harvesting contaminated shellfish. Research outputs will provide ecological data essential to management and restoration of regionally important shellfish and their habitat. 

Data collected as part of this study can be applied immediately to aid a number of identified local and regional endusers regarding land-use planning, temporal and spatial scales for future water quality sampling, and evaluation of shellfish sanitation indicators. This study addresses concerns within several MASGC priority areas, including:

  1. Testing a predictor that links land-use planning to water quality and ecosystem health,
  2. Assessing the responses of living resources to pollution and
  3. Testing and refining a method for more affective detection of biological contaminants in commercial shellfish.

Objectives

Our primary objective is to collect data that will enhance coastal economies by helping to maintain and restore local shellfish populations, increase the area of land available for shellfishing, inform efficient determinations of market-safe shellfish, and reduce the risk of harvesting contaminated shellfish.


Specifically, we propose to meet these objectives by:

  1. Clearly defining links between wastewater sources and effects on fisheries and human health
  2. Determining the spatial and temporal scales of WTP-related effects for management.

Methodology

We propose to team with the U.S. FDA on Dauphin Island to determine whether WTP discharge affects growth and survival of shellfish or their safety for human consumption.  We will take a novel approach to this problem by combining

  1. FDA measurements of a highly reliable enteric pathogen proxy (MSB) and the traditional fecal coliform test with
  2. Measurements of a natural tracer of anthropogenic wastewater sources (N stable isotopes)
  3. Measurements of potential wastewater-driven changes on shellfish habitat (DO) and food supply (nutrient and chl a concentrations)
  4. Measurements of variation in shellfish growth and survival through time. To determine spatial and temporal extent of wastewater influences, we will measure stable isotope ratios in tissues of sentinel bivalves (C. virginica) and particles in estuarine water at locations, varying in proximity from the WTP on McDuffie Island in Mobile Bay (parallel to existing FDA sampling sites).

Based on the results of year one, in year two we will choose sampling locations to best capture variation in dilution due to hydrology and level of WTP processing. To do this, we will either repeat our sampling at modified locations relative to the McDuffie WTP or shift our scheme to the lower flow, but higher treatment level WTP on Dauphin Island.

Rationale

Wastewater treatment plants (WTP) account for more than 30% of shellfish area closures in the U.S. and >70,000 ac in Mobile Bay. Shellfishing areas near WTPs are typically closed to fishing due to fecal coliform concentrations that may indicate human health risk. The reliability of this indicator, however, is uncertain. The FDA on Dauphin Island is testing an alternative indicator, male-specific bacteriophage (MSB), but lacks a method to definitely link their findings to wastewater sources. We offer a stable isotope approach that will

  1. Identify wastewater sources parallel with microbial indicators
  2. Help determine the spatial extent and time courses of these effects. 

This study addresses concerns within several MASGC priority areas, including

  1. Testing a predictor that links land-use planning to water quality and ecosystem health
  2. Assessing the responses of living resources to pollution
  3. Testing and refining a method for more affective detection of biological contaminants in commercial shellfish.

For more information, contact MASGC Research Coordinator Loretta Leist (Loretta.leist@usm.edu). Please reference the project number R/CEH-28.