Citation:

Oczkowski, A., I. Cappielo Cosme, M. Molina, Alana Hanson, M. Schwartz, E. Huertas, AND D. Katz. Contaminants play a key role in understanding ecosystem function in tropical urban estuaries. Ocean Sciences Meeting, NA, Virtual, February 24 - March 04, 2022.

Impact/Purpose:

Coastal ecosystems in tropical climates are severely understudied. We lack a basic understanding of how they function ecologically. Here, we use indicators of human impact, like fecal coliform and sucralose (an artificial sweetener) concentrations, to try to indirectly determine how much of an influence urbanization has on nutrient cycling in the tropical San Juan Bay Estuary.

Description:

Tropical urban estuaries are understudied and researchers often apply conceptual frameworks of ecosystem function developed for temperate systems to tropical ones. But it is becoming increasingly clear that the ecosystem dynamics driving tropical estuaries are different from temperate systems. Given concerns about human impacts on urban coastal waters and the dearth of tropical biogeochemical research, this study looked for indicators of human influence on the biogeochemistry and productivity of the San Juan Bay Estuary (SJBE) in San Juan, Puerto Rico. We observed a mismatch between high counts of fecal indicator bacteria (fecal coliform and Enterococci) but low dissolved inorganic nitrogen (N) concentrations and stable isotope values in SJBE waters. Sucralose and caffeine concentrations also indicated high human sewage loads. Very low N stable isotope values in the most urbanized stretches suggest that, despite bacterial and chemical indicators of extensive sewage contamination, the microbial community may be adding new N. Sewage N contributions may support only a small portion of the net ecosystem production and urban carbon contributions may be indirectly fueling ecosystem production in the most impacted regions of the estuary.

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