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

Abstract

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.