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Unusual biogeochemistry in a tropical, urban estuary --and the case of the clogged canal
Citation:
Oczkowski, A. Unusual biogeochemistry in a tropical, urban estuary --and the case of the clogged canal. Virginia Institute for Marine Science Seminar, Gloucester Point, Virgina, November 05, 2018.
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 filled waters. We have been studying the sediment in the estuary and in the nearby mangrove forests to examine the impact that the closed canal has on the whole system and the people that live near it. We have found that these polluted flood waters change the normal cycling of nitrogen which makes the water quality worse than it would normally be. As more people live near the coast in warm climates, it is important to understand these multiple effects so that good management decisions can be made about lessening the effects on the local population and wildlife.
Description:
Coastal cities in tropical areas are often low-lying and vulnerable to the impacts of flooding and storms. San Juan, Puerto Rico is a good example of this. It is built around a lagoon-channel complex called the San Juan Bay Estuary (SJBE). A critical channel in the estuary, the Caño Martín Peña, has filled in and now frequently floods the surrounding communities with sewage-enriched waters, causing a series of human health and ecological problems. Analyses of sediment core and surface sediment grab samples indicate deposition rates and levels of organic matter and nutrients have recently increased throughout the SJBE. Portions of the system are now functioning as settling basins. Stable isotope and sediment nutrient analyses indicate that while high urban and sewage runoff to the Caño contributes nitrogen (N), they may also enhance conditions for coupled sulfate reduction-nitrogen fixation. This source of ‘new’ N may meet or exceed that from urban runoff. The ecological consequences of runoff to the Caño extend beyond the ponded channel and are contributing to the poor water quality of the SJBE, greater than contaminated runoff alone.