Coastal marine environments have been impacted by human activity for several centuries, including shoreline alteration, nutrient introduction, sedimentation, toxic compound release, and thermal modification. Mt. Hope Bay, Massachusetts is an ideal site to base a study of human pathogen presence and distribution because it has several important sources of human impact, including sewage disposal sites and the thermal outfall of a power plant within a mile of each other. The Bay has undergone limited monitoring for several different parameters, including fish populations, river runoff, meteorological forcing, tidal cycles and water chemistry as part of the Mt. Hope Bay Natural Laboratory (MHBNL) program, a 5-year interdisciplinary project at the University of Massachusetts Dartmouth School of Marine Science and Technology (SMAST). While phytoplankton and zooplankton communities in the water column have been fairly well monitored, although not at a molecular level, microbial communities remain relatively uncharacterized. This project presents comprehensive (eukaryal, bacterial, archaeal) data from small-subunit ribosomal RNA gene clone libraries and next-generation Illumina amplicon sequencing for samples collected near the thermal plume and underlying sediments of the Brayton Point Power Plant. Not surprising, our findings reveal a highly diverse consortium of the three domains including relatives of sludge bacteria, polyaromatic hydrocarbon-degrading bacteria, and representatives related to the genera Staphylococcus, Streptococcus, and Clostridium. It is clear that even limited knowledge about the overall microbial community composition can lead to important observations about the ecosystem as a whole. Furthermore, understanding whether free-living pathogens participate in relationships with other members of the microbial community will be important in understanding their distributions and persistence.