| Microbial communities in nature, specifically marine sediment communities in the ocean, are responsible for biodegradation and other important biogeochemical cycles. Marine sediment microbial communities are particularly vulnerable to hydrocarbon and heavy metal pollution, so it is important to determine how these communities respond to environmental alterations, and if they are capable of recovering form this type of event. The microbial community structure in marine sediments from two different marinas on the east coast of Puerto Rico was studied for a period of 14 months. In microcosm studies with marine sediments incubated for a period of 8 weeks, the effects of exposure to naphthalene, cadmium, and nitrate were determined. Phospholipid fatty acid (PLFA) analysis, along with gas chromatography, were used to detect shifts in the microbial community structure due to disturbances. Principal component analysis (PCA) of the community PLFA profiles demonstrated large similarities between stations from different sites on most sampling dates, proving the existence of homogeneity in marine sediments from different locations. All microcosm samples showed variation in the microbial community structure, appreciable with PLFA profiles. Such shifts were indicative of changes in the species composition occurring within the microbial community, where more versatile and faster growing microorganisms dominated functional roles in the community. The sensitivity of the PLFA analysis, along with principal component analysis to study community-level responses to environmental alterations were demonstrated. |
