A septic waste index model to measure the impact of septic tanks on coastal water quality and coral reef communities in Rincon, Puerto Rico

Abstract

The impact of fecal contamination of coastal waters and coral reefs is a major cause of concern in marine reserves in Puerto Rico. The measurement of the association between septic tank frequency in watersheds of creeks draining into these reserves and coastal water quality and coral reef condition is of importance in configuring pollution control policy. Fecal coliforms and enterococci assays were used to measure the density of fecal contaminants across the Tres Palmas Marine Reserve (TPMR) in Rincon, Puerto Rico. Inshore waters are intermittent creeks, receiving fecal pollution only from faulty septic tanks. Fecal indicators measurements showed higher densities near the southernmost creek mouth emptying into TPMR, a finding consistent with a larger amount of dwellings with septic tanks within this watershed (Vista Azul creek). A Septic Weight Index was constructed to analyze sewage impact from all watersheds draining into the marine reserve. Linear Regression analyses showed a significant association between these non-point source fecal pollution sources and both coastal water quality and impact on some parameters measuring the condition of Acropora palmata coral reef colonies.