Linking sewage pollution and water quality to spatial patterns of Porites lobata growth anomalies in Puako, Hawaii

Sewage pollution threatens the health of coastal populations and ecosystems, including coral reefs. We investigated spatial patterns of sewage pollution in Puako, Hawaii using enterococci concentrations and δ15N Ulva fasciata macroalgal bioassays to assess relationships with the coral disease Porites lobata growth anomalies (PGAs). PGA severity and enterococci concentrations were high, spatially variable, and positively related. Bioassay algal δ15N showed low sewage pollution at the reef edge while high values of resident algae indicated sewage pollution nearshore. Neither δ15N metric predicted PGA measures, though bioassay δ15N was negatively related to coral cover. Furthermore, PGA prevalence was much higher than previously recorded in Hawaii and the greater Indo-Pacific, highlighting Puako as an area of concern. Although further work is needed to resolve the relationship between sewage pollution and coral cover and disease, these results implicate sewage pollution as a contributor to diminished reef health. •Abundant enterococci and high algal δ15N suggest sewage pollution in Puako.•Sewage pollution may influence Porites lobata growth anomalies (PGAs).•There is high spatial and temporal variability in sewage pollution entering reefs.•Physical factors (rainfall, hydrology, etc.) alter sewage and disease dynamics.•Long-term reef and pollution monitoring is needed in Puako.