Saltwater Intrusion On The Gulf Coast: An Assessment Of The Interactions Of Salinity Stress, Genetic Diversity And Population Characteristics Of Fish Inhabiting Coastal Marshes

EPA Grant Number: R829420E03
Title: Saltwater Intrusion On The Gulf Coast: An Assessment Of The Interactions Of Salinity Stress, Genetic Diversity And Population Characteristics Of Fish Inhabiting Coastal Marshes
Investigators: Leberg, Paul L. , Klerks, Paul L.
Institution: University of Louisiana at Lafayette
EPA Project Officer: Chung, Serena
Project Period: June 10, 2002 through June 9, 2004 (Extended to June 9, 2006)
Project Amount: $133,410
RFA: EPSCoR (Experimental Program to Stimulate Competitive Research) (2001) RFA Text |  Recipients Lists
Research Category: EPSCoR (The Experimental Program to Stimulate Competitive Research)


A consequence of climate change is the intrusion of saltwater into freshwater systems. Coastal Louisiana is currently experiencing higher than expected salinities in traditionally freshwater marshes and waterways. Studies of the effects of saltwater intrusion on resident animals are usually limited to documenting community changes. There has been little investigation of effects of saltwater intrusion on the demography and genetic structure. We propose to use the rapidly changing situation in Louisiana?s coastal marshes to understand how increasing salinity affects populations of resident fishes. Our objective is to examine how increasing salinity affects the ecology, demography, population structure, and genetic variation. The model organism for this research will be the western mosquitofish (Gambusia affinis) a wide spread and common predator that has been the subject of numerous studies on the effects of environmental stress on individual viability. We will test the hypothesis that increasing salinity is influencing genetic variation through demographic bottlenecks and local adaptation. We will also examine the hypothesis that fragmentation, associated with sea-level rise, will increase genetic differentiation among populations, as well as extinction of local populations.


We will assess demographic and genetic characteristics of populations exposed to different levels of salinity stress in both the field and experimental mesocosms. . Field sampling will be conducted in two separate hydrological basins across a salinity gradient including fresh, intermediate, and brackish marsh. We will assay genetic variation using microsatellite and allozyme markers to determine if increased salinity leads to changes in genetic diversity and interpopulation genetic differentiation through effects on population size and habitat fragmentation. Using mesocosms, we will determine if losses of genetic diversity, likely to occur with decreases in population size resulting from salinity exposure, affect the viability of fish populations in recovering freshwater environments, as well as in habitats with continued exposure to increased salinity. Experimental manipulations and field sampling will also be used to determine if a population?s history of exposure to increased salinity affects subsequent viability in brackish and freshwater environments.

Expected Results:

This research will contribute to our understanding of how saltwater intrusion affects animal populations and helps address efforts to protect and restore coastal marshes. The project will support efforts to develop a combination of field sampling, molecular assays, and experimental approaches using model organisms to address problems of environmental change in the state's coastal marshes.

Publications and Presentations:

Publications have been submitted on this project: View all 15 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 2 journal articles for this project

Supplemental Keywords:

coastal ecosystems, fish, fragmentation, genetic diversity, global climate, marshes, wetlands., RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, climate change, Oceanography, Aquatic Ecosystem, Environmental Monitoring, Atmospheric Sciences, Ecological Risk Assessment, Ecology and Ecosystems, wetlands, coastal ecosystem, climatic influence, fish habitat, global change, salt water intrusion, coastal environments, fish communities, fisheries, coastal ecosystems, ecosystem impacts, environmental stressors, estuarine ecosystem, habitat diversity, aquatic ecosystems, environmental stress, marsh ecosystem, aquatic ecology, global warming, sea level rise, ecosystem stress, genetic diversity, Global Climate Change

Progress and Final Reports:

  • 2002 Progress Report
  • 2003 Progress Report
  • 2004 Progress Report
  • Final Report