Abstract
Within the tropical marine study site of Guánica Bay, Puerto Rico, polychlorinated biphenyls (PCBs) are subjected to coastal and oceanic currents coupled with marine microbial and geochemical processes. To evaluate these processes a hydrodynamic model was developed to simulate the transport of PCBs within nearshore and offshore marine areas of Guánica Bay. Material transport and circulation information from the model were matched with measurements from samples collected from within the bay. These samples, consisting of both intertidal and submerged sediments, were analyzed for physical characteristics (organic carbon, grain size, and mineralogy), microbial characteristics (target bacteria levels and microbial community analyses), presence of PCBs, and PCB-degrading enzymes. Results show that the bay geometry and bathymetry limit the mixing of the extremely high levels of PCBs observed in the eastern portion of the bay. Bay bottom sediments showed the highest levels of PCBs and these sediments were characterized by high organic carbon content and finer grain size. Detectable levels of PCBs were also observed within sediments found along the shore. Microbes from the bay bottom sediments showed a greater relative abundance of microbes from the Chloroflexi, phylum with close phylogenetic associations with known anaerobic PCB-degrading organisms. Based on quantitative PCR measurement of the biphenyl dioxygenase gene, the intertidal sediments showed the greatest potential for aerobic PCB degradation. These results elucidate particular mechanisms of PCB’s fate and transport in coastal, tropical marine environments.
Highlights
Polychlorinated biphenyls (PCBs) are toxic to humans and are believed to constitute health hazards [1]
The objective of this study is to evaluate the influence of marine hydrodynamics on the microbial community characteristics in a marine environment impacted by PCBs
Releases tend to remain within the bay with the exception of sites closest to the outlet, S1 and H2, where transport occurs towards the outlet under northerly and southerly wind conditions
Summary
Polychlorinated biphenyls (PCBs) are toxic to humans and are believed to constitute health hazards [1]. Banned from manufacturing in the U.S [2] and other countries, adverse impacts from PCBs are observed throughout the world because of their widespread use in transformers and long-term persistence [3,4]. Many sites throughout the U.S are under considerable scrutiny for PCB contamination. The majority of these sites, under the U.S Superfund program which is responsible for remediating some of the nation’s most contaminated sites, are on land or river systems. Few PCB contaminated sites are observed in marine systems [5,6,7,8,9,10] In these environments, we anticipate unique coastal hydrodynamics, chemical transformations, and microbial responses, which in turn result in unique microbiomes within sediments and on marine flora
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