Grantee Research Project Results
2004 Progress Report: 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: R829420E03Title: 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 Period Covered by this Report: June 10, 2004 through June 9, 2005
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)
Objective:
A consequence of global climate change is the intrusion of saltwater into freshwater systems caused by increased sea level. Coastal Louisiana is currently experiencing higher than expected salinities in traditionally freshwater marshes, waterways, and reservoirs. Most research has focused on plant communities; studies of the effects of saltwater intrusion on resident animal populations usually are limited to surveys documenting species replacement. There has been little investigation of effects of saltwater intrusion on the demography and genetic structure of wetland populations of fishes. We propose to use this rapidly changing situation in Louisiana’s coastal marshes to understand how increasing salinity affects populations of resident fishes.
The objective of the research project is to examine how increasing salinity affects the ecology, demography, population structure, and genetic variation of these fishes. 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 also will examine the hypothesis that marsh fragmentation, associated with sea-level rise, will increase genetic differentiation among populations, as well as extinctions of local populations.
Progress Summary:
Several experiments have indicated that resident marsh fishes are either adapted and/or acclimated to the salinity levels of their environments; this response is seen in widely separated populations. These results suggest the possibility that resident fishes can adapt to increasing levels of salinity associated with sea level rise. We are currently determining if these differences are because of physiological acclimation or genetic adaptation.
There is considerable life history variation among populations of marsh fishes separated by relatively short distance. The majority of this variation does not appear to be related to salinity gradients; additional analysis will be needed to determine if some of these differences are because of habitat conversion and marsh fragmentation.
Analysis of genotypic variation among the field samples and experimental mesocosm experiments is progressing well. Levels of variation, detected at microsatellite loci, are high. Considerable additional data needs to be collected, however, prior to analysis.
Field sampling has revealed strong gradients in fish and invertebrate communities, even over short distances. These gradients are associated with salinity gradients; marsh fragmentation and habitat conversion, however, also are playing a role in influencing community structure. Analysis of field collections is near completion and the results should be submitted for publication shortly.
Future Activities:
During the subsequent reporting period, we will continue and complete work on the main components of the research project. These include: (1) seasonal field sampling to determine the role of increased salinity and marsh fragmentation on the community structure, population genetics, and demography of resident fish populations with continued focus on poeciliids; (2) a mesocosm experiment examining the influence of neutral and selective bottlenecks on the development of salinity resistance, population viability, and loss of genetic diversity; (3) a mesocosm/laboratory experiment assessing the role of past salinity exposure on adaptation and population viability in the face of increasing salinity levels; and (4) a mesocosm experiment examining the effects of increased salinity on breeding behavior and reproductive strategies of resident marsh fishes.
These components involve long-term seasonal sampling, which will extend to the end of 2005. Following this work, results will be analyzed and prepared for publication.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 15 publications | 3 publications in selected types | All 2 journal articles |
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Leberg PL. Genetic approaches for estimating the effective size of populations. Journal of Wildlife Management, 2005. 69(4): 1385-1399. |
R829420E03 (2004) R829420E03 (Final) |
not available |
Supplemental Keywords:
global climate, ecological effects, vulnerability, aquatic, ecology, salinity, adaptation, genetic variation, sea level,, RFA, Air, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Aquatic Ecosystem, Aquatic Ecosystems & Estuarine Research, Ecological Risk Assessment, Oceanography, Atmospheric Sciences, climate change, Ecology and Ecosystems, Environmental Monitoring, ecosystem impacts, environmental stressors, Global Climate Change, aquatic ecology, coastal ecosystems, global change, global warming, coastal ecosystem, marsh ecosystem, estuarine ecosystem, fish habitat, habitat diversity, wetlands, coastal environments, ecosystem response, ecosystem stress, environmental stress, salt water intrusion, fish communities, fisheries, climatic influence, aquatic ecosystems, genetic diversityRelevant Websites:
http://biology.louisiana.edu/leberg.html Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.