Grantee Research Project Results
1997 Progress Report: Developing a New Monitoring Tool for Benthic Organisms in the Gulf of Mexico: Loss of Genetic Variability in Meiofaunal Populations
EPA Grant Number: R825355Title: Developing a New Monitoring Tool for Benthic Organisms in the Gulf of Mexico: Loss of Genetic Variability in Meiofaunal Populations
Investigators: Montagna, Paul A. , Kennicutt, Mahlon C.
Institution: The University of Texas at Austin , Texas A & M University
EPA Project Officer: Hahn, Intaek
Project Period: December 1, 1996 through November 30, 1998
Project Period Covered by this Report: December 1, 1996 through November 30, 1997
Project Amount: $243,469
RFA: Exploratory Research - Environmental Biology (1996) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Aquatic Ecosystems
Objective:
The purpose of this project is to develop an understanding of the cause of genetic variability loss near offshore hydrocarbon production platforms. The thesis of this study is that selection can occur by chronic, sublethal exposure to contaminants and this can cause populations to lose genetic variability. If selection by contaminants is a general phenomenon, then this would have broad management implications and support the use measuring population structure at the molecular level as an ecological monitoring tool.Field and laboratory experiments were proposed to isolate the confounding factors of contaminant and reef effects that could explain population subdivision found in previous studies. The goal of the field experiment is to compare population structure at artificial reefs (inactive platforms without contamination), sites where platforms were removed (no reef but contaminants still exist), operating platforms (reef and contaminant effects), and control sites (normal shelf sediments at least 3 km away from natural or artificial structures). The goal of the laboratory experiments is to exposure organisms to specific contaminants (e.g., heavy metals, that exist at high levels at production platforms) over three generations to demonstrate that contaminants can cause selection.
Genetic variability in populations is measured using restriction fragment length polymorphisms of mitochondrial DNA. Mitochondrial DNA is useful in population studies because: it has a high divergence rate, is maternally inherited (eliminating recombination events), and is more abundant than nuclear DNA. Populations are differentiated by calculating a haplotype diversity index.
Progress Summary:
The field experiment was very difficult to plan, but was successfully carried out in August 1997. Locations were obtained for artificial reefs from the Texas Parks and Wildlife Department and for platform removal sites from the U.S. Minerals Management Service. The northwestern Gulf of Mexico was divided into three areas and a platform, reef, removal, and control site were sampled in each of the three regions. Therefore, we have a correctly replicated design at the treatment level with a total of 12 stations (=3 sites 4 treatments). Five replicates were taken at each station for meiofaunal community structure, harpacticoid diversity, and levels of sediment contaminants. The sediment chemistry analyses were completed by Texas A&M University (M.C. Kennicutt, principal investigator). Chemical contaminant backgrounds followed expected trends as illustrated by the average concentrations (in ppm) for all samples of the following tracers of hydrocarbon exploration and production:
Treatment "Site" |
Total Petroleum Hydrocarbons |
Barium | Cadmium |
Control | 3.3 | 432 | <0.01 |
Reef | 3.6 | 283 | <0.01 |
Removal | 5.0 | 641 | 0.03 |
Platform | 5.4 | 563 | 0.06 |
Organismal samples are still undergoing the labor intensive sorting and species identification phase. However, we have also begun genetic analyses on samples that have been sorted. The major activity that we accomplished during the Fall of 1997 was to finalize protocols for the genetic analyses. At the current time, we can perform genetic analyses as organisms are prepared from samples.
The laboratory exposure experiments are nearly complete. These were carried out in conjunction with Dr. John Fleeger, Louisiana State University. Approximately 300 adult female Nitocra lacustris were collected from the field for the experiment. Previously, we had identified levels of metal contaminants that were associated with reduced genetic variability around offshore platforms. Therefore, the organisms were cultured in a mixture of 50 g l-1 Zn, 37.5 Pb and 0.25 Cd. Organisms were fed a mix of MicroFest and algae each time the culture is set up. There were two treatments (metals and 25 ppt sea water) and two replicates per treatment (four cultures). The initial cultures are identified as the parents (P generation) and three generations of offspring (F1-F3) were cultured and collected. Subsamples of 50 individuals were collected and preserved in alcohol for each generation. The experiment was completed in late December, and genetic analyses will begin shortly.
Future Activities:
Both experiments were performed as planned in the proposal. In fact, replication was increased substantially over that proposed as suggested during the proposal review process. Currently, work on genetic analyses is beginning.Journal Articles:
No journal articles submitted with this report: View all 7 publications for this projectSupplemental Keywords:
water, marine, ecological effects, sensitive populations, genetic polymorphisms, PAH, heavy metals, indicators, EPA Region 6, petroleum., RFA, Scientific Discipline, Waste, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Ecosystem/Assessment/Indicators, Ecosystem Protection, Contaminated Sediments, Environmental Chemistry, Genetics, Ecological Effects - Environmental Exposure & Risk, Monitoring/Modeling, Biology, Ecological Indicators, Gulf of Mexico, ecological exposure, monitoring, environmental monitoring, fish kills, benthic organism, contaminated sediment, meiofaunal populations, ecosystem health, hydrocarbons, genotypes, genetic damage, benthic organismsRelevant Websites:
http://www.utmsi.utexas.edu/staff/montagnaProgress 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.