Grantee Research Project Results
2003 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, 2003 through June 9, 2004
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 as a result of increased sea level. Coastal Louisiana currently is 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 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 populations of resident fishes.
The objective of this 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 is 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 are testing the hypothesis that increasing salinity is influencing genetic variation through demographic bottlenecks and local adaptation. We also are examining the hypothesis that marsh fragmentation, associated with sea-level rise, increases genetic differentiation among populations, as well as extinctions of local populations.
Progress Summary:
Results of the salinity mortality experiments indicate that resident marsh fishes with a history of salinity exposure are much more resistant to high levels of salinity than fish from freshwater marshes. Gambusia from brackish marshes either are adapted and/or acclimated to the salinity levels of their environments. We now are in the process of determining if these differences are attributed to physiological acclimation or genetic adaptation. Results of these comparisons should be available soon.
Preliminary results of a mesocosm experiment indicate 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. We currently are completing our assessment of genetic variation from these populations using eight highly polymorphic microsatellite markers.
Results of the initial field sampling exhibit a striking gradient in fish communities, even over short distances. These gradients are associated with salinity gradients; however, the level of marsh fragmentation also appears to play a role in which fishes are present. We now are trying to determine if fragmentation effects are independent or associated with saltwater intrusion in the coastal marshes. Sampling of field and mesocosm populations is ongoing.
Future Activities:
During the subsequent reporting report, we will continue work on the main components of this 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.
(4) A series of survival experiments to evaluate the genetic basis of salinity tolerance in populations from a history of salinity exposure.
These components involve long-term seasonal sampling, which will extend at least through much of the next reporting period.
In addition to the components outlined in the original proposal and those listed above, we are expanding this research 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, air, ecosystem protection/environmental exposure and risk, aquatic ecosystem, aquatic ecosystems and estuarine research, atmospheric sciences, ecological risk assessment, ecology and ecosystems, oceanography, climate change, global climate change, aquatic ecology, climatic influence, coastal ecosystem, 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, saltwater intrusion, sea-level rise,, 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.