Athens, Ga.
– A new University of Georgia study finds that sewage-contaminated
groundwater is reaching the offshore reefs of the Upper
Florida Keys, possibly threatening corals and human health.
“The widespread use of in-ground waste disposal through
septic tanks and injection wells appears to be leading to the contamination of
submarine groundwater even up to six miles offshore,” said study author Erin
Lipp, associate professor at the UGA College of Public Health. “When the
contaminated groundwater mixes with surface water and reaches the reef, the
corals as well as human health might be harmed.”
The findings were presented Tuesday at a meeting of the
Florida Keys National Marine Sanctuary Water Quality Protection Program
Steering Committee in Marathon,
Fla.
Lipp and doctoral student Carrie Futch, along with Dale
Griffin of the U.S. Geological Survey in Tallahassee,
sampled surface water, groundwater and corals from five sites from nearshore to
offshore beginning outside of Port
Largo Canal
and ending near Molasses Reef. Their three-year study revealed common fecal
indicator bacteria and human viruses.
The fecal indicator bacteria, which are not pathogens
themselves but rather serve as surrogates for other disease-causing microbes
found in sewage, declined with distance from shore but tended to be elevated in
the surface layers of coral mucus relative to the surrounding water. High levels
of fecal indicator bacteria from canals were also shown to move into the
nearshore environment on outgoing tides. Lipp said the detection of these
bacteria in predominantly nearshore stations suggests that land-based sources
of sewage pollution such as cesspits and septic systems may be a significant
contributor.
Genetic material from enteric viruses, which cause disease
in humans but are only found in infected human feces and urine, also were
commonly found throughout the sampled area, including ground water more than
six miles offshore. The frequency of detecting viruses increased with rainfall
in the summer months, when the viruses were most likely to be found in
groundwater. Lipp cautioned, however, that the test used to identify the
enteric viruses was not designed to determine whether the viruses were alive or
dead.
“Until we actually know the level of risk, our findings are
just an indication that there could be some level of sewage contamination
offshore,” she said. “It doesn’t indicate that people need to change their
behavior, but does show that the appropriate treatment of water through
centralized sewage is needed.”
Bill Kruczynski, Florida Keys Program Scientist for the U.S.
Environmental Protection Agency, said the installation of new wastewater
management systems such as centralized collection and advanced wastewater
treatment facilities, as recommended by the Water Quality Protection Program
(WQPP) for the Florida Keys National Marine Sanctuary and required by Florida
State Law 99-395, is essential to restore and maintain water quality in the
Florida Keys. In addition, the WQPP recommended improved storm water treatment
practices to further reduce pollutant loading to nearshore waters.
“The Sanctuary and Monroe County
are taking the right steps to improve water quality by enacting no dumping
ordinances and implementing centralized sewage,” Lipp said. “The next step is
to ensure that it’s working and hopefully document an improvement in water
quality.”
The study was funded by the U.S. Environmental Protection
Agency.
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