This review of sewage management in Puerto Rico highlights widespread dependence on septic tanks (>50%) and ample anecdotes of leaking or overflow events resulting from high precipitation. This study investigated the impact of septic tanks on coastal water quality, coral reefs, and beaches with a focus on human health and ecological impacts. Water quality measurements (temperature, pH, salinity, dissolved oxygen, Enterococcus, and turbidity) were taken while a spatial analysis of drainage into the Tres Palmas Marine Reserve (TPMR) was done using GIS, arial photos, and data from the Puerto Rico Aqueducts and Sewer Authority. Habitat impacts were assessed by quantifying the presence and condition of both living and dead Acropora palmata (Elkhorn coral) to determine the Live Area Index (LAI) of corals. These measurements all contributed to creation of the Septic Weight Index (SAI) model. Scientists used the quantity, distance to water body, and distance to sampling station of septic systems to quantify the relationship between sewage pollution and microbial densities. Analysis using the SAI resulted in a linear association between sewage pollution and the distribution and bleaching of Elkhorn coral colonies. Additional linear associations between the SAI and the percentage of living tissue cover as well as percentage of mortality suggest that sewage pollution has a negative impact on coral reefs. The models used in this paper can be adapted for other study sites to improve understanding of how the density and location of septic systems impact adjacent waters, including marine reserves. This research demonstrates that consideration of nearby sewage sources is critical for coral reef conservation and marine protected areas should take this into account in their management plans.
Authors: Norat-Ramírez, J., P. Méndez-Lázaro, E.A. Hernández-Delgado, H. Mattei-Torres, and L. Cordero-Rivera
Year: 2019
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Email for the full article: resilience@tnc.org
Ocean & Coastal Management 169: 201-213. doi:10.1016/j.ocecoaman.2018.12.016
