The cleanest beach may not be so clean. A new UCLA study has
shown that even if ocean water tests meet health standards, the
sand itself may still be contaminated with bacteria.
With the sizzle of summer only a few weeks away, Southern
Californians are preparing for long summer days filled with
surfing, sailing and playing in the sand.
But while the sparkling blue water may be clean, the
beach’s sand could very well be harboring the bacteria the
ocean water isn’t, according to the UCLA study being
published in the next issue of the Water Research journal.
The Web site for the Los Angeles County Department of Health
Services Ocean Water Monitoring Program states that beaches are
closed when sewage or chemical spills contaminate ocean water. The
bacteria discovered by the UCLA research team, which is the same
bacteria tested for in ocean water, is associated with fecal matter
and can be found in sewage.
“I don’t think anybody in the world regulates
bacteria in sand. … People should be cognizant that there are
bacteria in sand. I think they need to take appropriate
precautions,” said Alexis Strauss, director of the Water
Division for the U.S. Environmental Protection Agency.
The EPA does not monitor the bacterial levels in sand.
“More studies are under way. … There aren’t any
standards for bacteria in sand to measure against, in terms of what
is high risk, but it is certainly useful information,”
Strauss added.
After a storm event Jennifer Jay, a professor at the UCLA Henry
Samueli School of Engineering and Applied Science, and her student
researcher headed to the beach with their science equipment to see
what they could dig up.
While Jay noted that water levels had risen and dropped with the
passing of the storm, the sediment levels had surprisingly followed
a similar pattern as well.
“We had a hypothesis that the sand would surface reservoir
with bacteria,” Jay said.
After collecting sand samples from 11 open and two enclosed
Santa Monica Bay beaches, the researchers tested their samples to
see if the sediments could support the growth of microorganisms.
They did.
The researchers also performed a survey of the same beaches on
the same day.
The sand was tested for indicator bacteria which include
Escerichia coli and enterococci. E. coli has a variety of different
strains, some beneficial kinds that reside in our intestines and
other harmful ones that can lead to food poisoning.
The indicator bacteria are used to test beach water for the
presence of pathogens, or disease-causing microorganisms.
“The two enclosed beaches showed 1000 times higher levels
of indicator bacteria (in sand) versus open beaches,” Jay
said.
These bacteria are used as indicators of bacterial contamination
in place of other pathogens because they are easily tested for in a
laboratory setting. The immense diversity of pathogens makes it
difficult to test for each one individually.
The research increases the need for beach cleanup and may result
in the posting of warnings, said Mark Gold, executive director of
Santa Monica-based Heal the Bay.
Though the ocean water of one of the enclosed beaches had tested
clean, the sand still sustained indicator bacterial growth.
“It brings up questions about the sediment reservoir.
It’s known that the indicator bacteria and pathogens can
persist longer in sediment than water and they can grow in
sediments,” Jay said.
The high levels of indicator bacteria in enclosed beaches can be
due to myriad reasons, including the possibility of contamination
from ocean water as it flushes the sand.
“It probably has something to do with the amount of
flushing of clean water that goes over the sand but we feel it may
be more complicated than that,” Jay said.
The amount of bacteria also changes based on the time of
year.
“There may be seasonal effects. It could have to do with
the whole microbial community and how they vary with the
seasons,” she added.
The next step in the research project is to determine if there
is a link between the indicator bacteria levels and pathogen levels
in the sand.
Jay will give a lecture about her research at 7 p.m. tonight at
the engineering school.
With reports from Bruin wire services.