Cryptofauna as Indicators of Benthic Community Health at the Waianae Ocean Outfall

Abstract

The City and County of Honolulu Department of Environmental Services has been monitoring the effects of treated wastewater effluent on benthic communities located near the Waiʻanae ocean outfall since 1989. The results consistently show no significant effects to community composition, mostly polychaete worms (0.5-10 mm). However these analyses were performed on the community as a whole, with little focus on the cryptofaunal component. It is shown here that the cryptofaunal communities can be bioindicators of environmental change given a sufficient habitat and population of indicator species such as Syllid polychaetes. Cryptofaunal communities reveal a similar pattern of mostly insignificant effects by the presence of the outfall, but visible differences exist between reference and outfall stations in years 2010 and 2012. The decrease in the population of Syllid polychaetes near the outfalls during those two years is not consistent with effects associated with nutrient enrichment, but rather with sediment grain size.