ASSESSING SALT MARSH HEALTH: A TEST OF THE UTILITY OF FIVE POTENTIAL INDICATORS

We examined the utility of five measures of salt marsh function, focusing on angiosperms and microbes, as potential indicators of salt marsh health. We studied twelve salt marsh creeks around Charleston Harbor, South Carolina, USA, six of which were polluted with metals and/or organic compounds and six of which were relatively pristine. Physical variables (sediment clay-silt content, creek water salinity) did not differ between impacted and reference sites. Microtox toxicity measures (expressed as wet or dry units) did not differ between impacted and reference sites. Photosynthesis and transpiration rates of creekbank Spartina alterniflora did not differ between impacted and reference sites, nor did measures of peroxidase activity in S. alterniflora. The glutathione concentration of S. alterniflora was lower at impacted sites than at reference sites; however, glutathione concentration did not respond to pollution in an earlier study in Georgia, likely because glutathione responds differently to particular chemicals rather than being a generic indicator of plant stress. Overall, these measures showed little promise as rapid indicators of salt marsh health. Other methods, such as quantifying benthic invertebrate taxa, may be more reliable for assessing ecosystem health in salt marsh systems.