Temporal variability of fecal indicator bacteria during spring tides.

摘要

Fecal indicator bacteria (FIB) concentrations were measured in ankle deep water at 10 sites in Balboa Island, CA and Dana Point, CA from October 17, 2009 to February 12, 2010 before and after morning high tide for 6 spring tide events. When samples were analyzed one hour after high tide, 3 out of 10 sites yielded a significant increase in FIB concentrations and exceeded ocean recreational water quality standards. These 3 sites were located either next to creek outlets that were considered the source of FIB or storm drains that consistently produced high concentrations of FIB. Sites further away from pollution sources showed an overall decline in FIB concentration after high tide but results were inconsistent. FIB decline may be due to dilution by cleaner ocean water brought in by tides. Drastic changes in water quality associated with spring tides suggest that these changes should be considered when sampling by beach monitoring programs. It also suggests that creek and storm drains are not only contaminating the ocean by direct flow but may also be contaminating the surrounding coastal land area. FIB-enriched sand, decaying wrack and animal feces from runoff may be possible contaminants.