Response of a salt marsh microbial community to inputs of heavy metals: Aerobic heterotrophic metabolism

Abstract

The addition of a sterilized, sludge-based fertilizer to experimental salt marsh plots increased both the nitrogen and the heavy metal content of the surface sediment. Aerobic heterotrophic microorganisms collected from these plots differed from microbes collected from control plots in their oxygen uptake rates on a uniform sediment medium both in the presence and absence of metals. When metals were not present, microbes from fertilized plots took up significantly less oxygen that did microbes from control plots. In the presence of metals, oxygen uptake by microbes from both plots was depressed; however, activity of microbes from the fertilized plots was significantly less inhibited than was that of microbes from the control plots, indicating a greater degree of metal tolerance in the former. To assess the effect of a metal on the microbial community in the absence of nutrient enrichment, chromium solutions were applied to several 1-m2 marsh plots. Microbes from these plots developed a tolerance to both copper and chromium within 1 month. The oxygen uptake on sediment media in the absence of metals did not differ from that demonstrated by nonmetal-tolerant microbes.