Oregon Beach Monitoring Program: Bacterial exceedances in marine and freshwater creeks/outfall samples, October 2002-April 2005.
A total of 3086 samples, both marine (2916) and freshwater creeks/outfall samples (170) were collected and analyzed for enterococci during October 2002-April 2005, from 52 designated beaches in Oregon. A total of 3.2% (99/3086) of the samples at 21 beaches exceeded 158 most probable number (MPN)/100 milliliters (mL). The average enterococci levels of these 99 exceedances was 559 MPN/100 mL, with a maximum of 4352 MPN/100 mL (Otter Rock and Ona) and a minimum of 160 MPN/100 mL (Sunset Bay State Park, Bastendorff, and Mill). For marine water, 77/2916 (2.6%) exceeded 158 MPN/100 mL. For freshwater, 22/170 (12.9%) exceeded 158 MPN/100 mL, with a maximum of 587 MPN/100 mL at Sunset Bay. Sixty percent of the marine and 9% of freshwater exceedances occurred during the winter. Seventy-two percent (55/77) of the marine exceedances occurred after rainfall events (0.01-60.0 mm). At Harris and Mill Beaches, cumulative rainfall was highly correlated with bacterial densities, R = 0.7. Rainfall, at both beaches, explained about one-half the variation in log10 bacteria density (R2 = 0.5). Additional monitoring is warranted to further characterize bacterial contamination in Oregon waters.
Neumann
C M
CM
Department of Public Health, 310 Waldo Hall, Oregon State University, Corvallis, OR 97331, USA. cathy.neumann@oregonstate.edu
Harding
A K
AK
Sherman
J M
JM
D001493:Bathing Beaches; D015169:Colony Count, Microbial; D016983:Enterococcus / Q000302:isolation & purification*; D004784:Environmental Monitoring; D006078:Government Programs; D016014:Linear Models; D009922:Oregon; D011891:Rain; D045483:Rivers / Q000382:microbiology; D012621:Seasons; D012623:Seawater / Q000382:microbiology; D013997:Time Factors; D014871:Water Microbiology