Elevated
bacteria counts in stormwater can indicate the presence
of disease-causing bacteria and viruses, and may eventually contaminate
waterways. One potential source of bacterial pollution is
from improperly maintained residential septic systems
or
improperly
disposed
pet wastes.
Although they are still monitored, many of the "indicator bacteria"
used on the mainland (e.g. fecal coliforms and enterococcus) are not
effective
at
predicting
sewage
contamination in tropical
climates like Hawai‘i.
:
;Aquatic life
;Water Quality
Total Coliform:
Coliform bacteria originate from soils, plants and human and animal wastes. On the mainland, the presence of high numbers of coliforms in a water body is used as an indicator that the water is polluted with harmful microorganisms and viruses (ref). However, in tropical climates, coliform bacteria is common in the soil and it's presence does not necessarily indicate pollution(ref).
Fecal Coliform:
Fecal Coliform is a specific kind of bacteria that is found primarily in the intestinal tracts of mammals and birds. In tropical climates, such as Hawai‘i, these bacteria are common in the soil, and their presence in water samples does not necessarily indicate the presence of sewage contamination (ref). If they are present in high concentrations in recreational waters and are either ingested or enter the skin through a cut or sore, they may cause disease, infections or rashes (ref).
Enterococci:
On the mainland, enterococcus is one of the most useful types of indicator bacteria for determining the extent of sewage contamination of surface waters (ref). However, in Hawai‘i, environmental sources of enterococcus reduce its value as a water quality indicator (ref).
Ratio of Fecal Coliform to Fecal Streptococci :
The ratio of Fecal Streptococci to Fecal coliform (FS/FC) used to be used to determine the source of bacteria. If the ratio was > 4, than the source was thought to be human, and if it was < 0.7, it was thought to indicate either livestock or poultry waste. However, this test is no longer considered reliable and is not recommended (ref).
Clostridium perfringens :
Fecal coliforms and enterococci are common in tropical soil, so their presence in water does not necessarily indicate sewage contamination. Clostridium perfringens is thought to be the most valuable "indicator" bacteria for tropical locations like Hawai‘i, and the Hawai‘i Department of Health has begun to monitor C. perfringens more regularly since it has been found to be a more reliable indicator of sewage contaminination (ref).
Staphylococcus aureus :
Staphylococcus aureus is a human pathogen which primarily affects the very old, the very young, and the very sick. It cannot survive long in water, but if it is present, it may cause illness (ref).
Fecal streptococci :
Fecal streptococcal bacteria are present in the intestine of warm-blooded animals and are ubiquitous in the environment (ref).