Una actualización del estudio EPA-Oficina de Investigación y Desarollo en CMP y los próximos pasos: Nutrient dynamics in a tropical urban estuary indict unanticipated nitrogen sources as contributing to environmental health problems—a case study from San Juan, Puerto Rico
Citation:
Oczkowski, A., Alana Hanson, AND E. Huertas. Una actualización del estudio EPA-Oficina de Investigación y Desarollo en CMP y los próximos pasos: Nutrient dynamics in a tropical urban estuary indict unanticipated nitrogen sources as contributing to environmental health problems—a case study from San Juan, Puerto Rico. Community Stakeholders, San Juan, N/A, PUERTO RICO, March 01 - 02, 2019.
Impact/Purpose:
Coastal cities in tropical areas are often low-lying and vulnerable to flooding. Portions of San Juan, Puerto Rico are a good example of this. A canal that used to connect lagoons in the San Juan Bay Estuary has filled in with sediment and debris and the communities adjacent to the canal are frequently flooded with sewage-enriched waters. Here we look at the biogeochemistry of the sediments in the estuary and the peat of the mangrove forests to document the ecological impact of the closed canal on the whole San Juan Bay Estuary. As tropical urban areas are so understudied, we make new observations about nutrient cycling in the region and suggest that the polluted flood waters create conditions that enhance the contributions of bioavailable nitrogen via nitrogen fixation by microbes. Thus, compounding water quality issues in the region.
Description:
Coastal cities in tropical areas are frequently low-lying and vulnerable to the impacts of flooding and storms. San Juan, Puerto Rico is a good example of this. The city is built around the San Juan Bay Estuary (SJBE), a complex of lagoons and channels. A critical stretch of the estuary, the Caño Martín Peña (CMP), has filled in with sediment and debris and now frequently floods the surrounding communities with sewage-enriched waters, causing a series of human health and ecological problems. Fecal coliform levels in the SJBE typically exceed acceptable limits, often by several orders of magnitude. But, dissolved inorganic nitrogen (N) levels are lower than expected, even in areas known to be enriched with sewage. A biogeochemical analysis of surface sediments from throughout the SJBE surprisingly indicated that N-fixation may be the primary source of bio-available N in the most impaired region, the CMP. Although sewage is characterized by high N stable isotope values (>8 ‰), they were low in this area (~2 ‰) and sulfur isotope values were the greatest in this stretch of the system (> 0‰), consistent with the presence of pyrite and reduced conditions. Similarly, mangrove peat adjacent to the CMP was characterized by high rates of nitrous oxide fluxes and high concentrations of N in the microbial biomass. We suggest that biogeochemical cycling in nutrient enriched tropical urban estuaries and associated wetlands may yield additional unaccounted for N that further contributes to eutrophied conditions and poor water quality.