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Characterization of the Oxidative Stress Response of Marsh Plants for Detection of Sub-Lethal Stress from Chemical Pollutants

PIs: Victor Dan Wall (formerly: Marine Institute, Sapelo Island, GA -- presently, U.S. Environmental Protection Agency, Denver, CO)

Support: Georgia Sea Grant College Program (R/WQ-2)

Timeframe: 3/1/97 - 2/28/99 (complete)

Project Overview:
A) Selected anti-oxidant responses of Spartina alterniflora and Juncus roemerianus to chemical and environmental stress were characterized. Spartina alterniflora is fairly resistant to the effects of Hg2+ as compared to other plant species. For this reason the research focused on antioxidants which have been shown in other plant species to be sensitive to contaminant effects (ie peroxidase and total glutathione). B) Chemical pollutant concentrations in sediments from selected sites were determined. C) The hypothesis that pollutant-induced changes in anti-oxidant components are valuable as predictors of the health of saltmarsh plant species and/or the saltmarsh as a whole was tested at the LCP Superfund site. This was accomplished by comparing responses from selected reference and chemically impacted sites and correlation with sediment contaminant concentrations. D) The work to date has been integrated closely with an EPA-funded project to allow meaningful comparisons of data across trophic and organizational levels.


  • A series of experiments were conducted to look at the response of S. alterniflora and J. romerianus to Hg2+ exposure:
    1. Peroxidase activity (POD) and total glutathione concentrations (tGSH) of the youngest leaf of Spartina alterniflora in hydroponic cultures increased in a dose dependent manner in response to Hg2+.
    2. POD and tGSH were significantly different from controls at concentrations of 0.1 and 0.01 ppm Hg2+ and higher, respectively, as compared to the 10 ppm required for a significant depression of rates of photosynthesis (PS) and transpiration (TS)
    3. POD and tGSH responses were confounded by transient exposure to elevated salinity
    4. As the summer progressed S. alterniflora was less and less affected by Hg2+.
    5. No measured responses of J. romerianus were indicative of Hg2+ exposure.

  • In the field, POD was significantly higher at the low salinity, high marsh site and was lowest in the high salinity, high marsh site. The reasons for this are unclear and the results are contradictory to the findings of the mesocosm salinity experiments. This effect was exaggerated by high tides and is probably related to rates of photosynthesis.

  • Chemical pollutant concentrations were measured in sediments collected from the LCP Superfund site in Brunswick, GA as well as reference areas along the Turtle River and on Sapelo Island. Composite samples were sent to the Skidaway Institute of Oceangraphy for total Hg, methyl Hg analysis by Dr. Ralph Smith and congener specific PCB analysis by Dr. Keith Maruya.

  • POD and tGSH levels were higher at the reference sites (Turtle river and Sapelo Island) than at the LCP site. Analysis of the data will focus on correlations of sediment chemical concentrations with measured responses. Within the LCP site peroxidase activity was weakly correlated with methyl mercury sediment concentrations. This is a preliminary analysis and subject to refinement when all the data is finalized.

Saltmarsh Fungi and Toxic Pollutants. S. Newell and V.D. Wall. Mycologia (Submitted).

Portions of this work were presented in a progress report submitted to the EPA for the project entitled "Health Indicators for Salt Marsh Estuaries of the South Atlantic Bight".

Planned Publications:
Biochemical and Physiological Changes of Saltmarsh Plants to Mercuric Chloride and Environmental Factors. V.D. Wall, H. Jacobs, A. Eastwood, D. Moore and S. Pennings. Marine Env. Res.

The Effect of Mercury and PCBs on the Formation and Processing of Detritus in a Georgia Saltmarsh. V.D. Wall, S. Pennings, R. Kneib, S. Newell and J. Alberts.

Biochemical and physiological changes of salt marsh macrophytes in response to mercuric chloride exposure: I. The effect of mercuric chloride. Heather E. Jacobs* (Lycoming University), Aletha L. Eastwood* (University of Kentucky) , Steven C. Pennings and V. Dan Wall. Georgia Journal of Science (Abstracts).

Biochemical and physiological changes of salt marsh macrophytes in response to mercuric chloride exposure: II. The effect of sodium chloride and environmental factors.
Aletha L. Eastwood* (University of Kentucky), Heather E. Jacobs* (Lycoming University), Steven C. Pennings and V. Dan Wall. Georgia Journal of Science (Abstracts).

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This page was updated October 13, 2006