Bacteriological monitoring studies to identity sources of fecal pollution at Baby Beach, Dana Point Harbor, California

Abstract

Summary form only given. Baby Beach, at Dana Point Harbor, CA has had a history of impaired water quality resulting in frequent beach postings and closures due to high fecal indicator bacteria concentrations, especially Enterococcus spp. Numerous Best Management Practices (BMPs) to reduce bacterial levels have been implemented, yet the postings continue. Weekly bacteriological monitoring data indicate a general decline in concentrations of fecal and total coliform bacteria from 1999-2002, suggesting some benefit of current BMPs such as storm drain plugs and netting to discourage bird nesting. However, enterococci concentrations increased during the same period. Bacterial monitoring studies to identify potential sources of indicator bacteria such as storm drains, birds, and sediments were conducted. The study objective was to assess groundwater, storm drains, seagulls, sediments, and increased boating and beach bathing activities as source of fecal indicator bacteria. Coastal sediments/sands may serve as a reservoir of fecal indicator bacteria from multiple sources including animal and human feces and plants. Sediment/sands can filter bacteria present in water and also provide protection from sunlight and predation. Sediments can also provide organic nutrients that enhance bacterial accumulation persistence and/or regrowth. Bacteria in sediments may affect levels in the overlying water. Storm drains can be significant sources of bacteria, nutrients and sediments that pollute receiving waters. Thus, densities of fecal indicator bacteria (total coliforms, fecal coliforms, E. coli and enterococci) in sediment and water samples collected along transects at nearshore sites and neighboring storm drain outfall area were determined using the membrane filtration method (American Public Health Association, 1998). Enterococcus species in water and sediments were determined using different identification methods, including API 20 STREP (Biome/spl acute/rieux), MicroScan/spl reg/ (Dade-Behring) and conventional biochemical testing. The bacteriological investigations conducted suggest that bacteria laded sediments, storm drains and seagull stools are major sources of fecal indicator bacterial pollution at Baby Beach.