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