Grantee Research Project Results
2002 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, 2002 through June 9, 2003
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:
The objective of this research project is to examine how increasing salinity affects the ecology, demography, population structure, and genetic variation of fishes. The model organism for this research will be the western mosquitofish (Gambusia affinis), a widespread 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.
A consequence of global climate change is the intrusion of saltwater into freshwater systems as a result of increased sea level. Coastal Louisiana currently is experiencing higher than expected salinities in traditionally freshwater marshes, waterways, and reservoirs. Most of the research has focused on plant communities. Studies of the effects of saltwater intrusion on resident animal populations are usually limited to surveys documenting species replacement. There has been little investigation of the 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 resident fish populations.
Progress Summary:
Results of the preliminary salinity mortality experiments suggest that resident marsh fishes are either adapted and/or acclimated to the salinity levels of their environments. If this result holds in additional experiments, it opens up the possibility that resident fishes can adapt to increasing levels of salinity associated with sea-level rise. The next step is to determine if these differences are because of the physiological acclimation or genetic adaptation. We now are in a position to test this hypothesis with a large number of juvenile fish that had parents from different populations with different histories of salinity exposures.
Preliminary results of a mesocosm experiment, completed during Year 1 of the project, suggest a strong influence of bottleneck history on population growth, as well as a positive response of population performance to manipulations designed to increase levels of genetic variation. These results suggest that manipulations of populations to increase levels of genetic variation, following a bottleneck, would have positive effects on population survival. However, the data analysis is preliminary and we need to complete a more through analysis of the population data, as well as complete our assessment of levels of genetic diversity using microsatellite DNA.
Results of initial field sampling exhibit a striking gradient in fish communities, even over short distances. These gradients are associated with salinity gradients; however, we are in the very early stages of data collection and analysis, preventing us from making statements regarding how population processes are being affected by rising water, marsh fragmentation, and increased salinity. Sampling of field and mesocosm populations is ongoing.
Future Activities:
During the next reporting period, we will continue 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; and (3) a mesocosm/laboratory experiment assessing the role of past salinity exposure on adaptation and population viability in the face of increasing salinity levels.
These components involve long-term seasonal sampling, which will extend at least through the end of Year 2 of the project.
In addition to the components outlined in the original proposal, and those that are highlighted above, we are expanding the project to examine the effects of increased salinity on breeding behavior and reproductive strategies of resident marsh fishes.
Journal Articles:
No journal articles submitted with this report: View all 15 publications for this projectSupplemental Keywords:
global climate, ecological effects, vulnerability, aquatic, ecology, salinity, adaptation, genetic variation, sea level., 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 ChangeRelevant Websites:
http://www.louisiana.edu/Departments/BIOL/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.