Volume 6, Spring 2008 - Saddleback College

Fall 2007 Biology 3A Abstracts
Beach, San Clemente, California
Nicole Baumgartner and Karl Neil
Department of Biological Science
Saddleback College
Mission Viejo, CA, 92692
Seven, one-hundred milliliter samples of beach water collected in front of a sewage
run-off in San Clemente, California, were analyzed using multi-tube fermentation to
determine if three days is a sufficient amount of wait time before people can re-enter
recreational waters following a rainstorm. Three portions of 10, 1, and 0.1 milliliters of
samples collected were added to nine lactose fermentation tubes, three into triple strength
brother, and 6 into single strength broth, respectively. Measuring total coliform bacteria
and using an index of Most Probable Numbers, confidence intervals for each sample were
obtained, determined by the positive presumptive test of acid production in the tubes. Gas
production was also monitored as a second indicator of bacterial presence. Days that
rained were found to have the largest amount of tubes showing positive presumptive
results. Days without rain were found to be negative for acid production. However, these
results were inconclusive due to a small data set. Due to the inconclusiveness of these
results, this study accepts the current three days suggested wait time, as it cannot conclude
from the data that less time will suffice.
Introduction
Water pollution is caused by many factors
and cannot be attributed to just one person or one
type of pollution. Increased urbanization minimizes
natural surroundings that biologically filter pollution
before it reaches the ocean and increases the number
of suitable surfaces where pathogens can grow and
multiply. Despite California’s history of battling
water pollution, beach closures due to heightened
levels of bacteria occur frequently up and down the
coast every year. A number of ocean-goers report
illnesses including ear and eye infections,
gastrointestinal problems, and rashes from excessive
levels of coliform bacteria (Gaffield et al, 2003.).
Thus, each rain washes potentially harmful levels of
bacteria into our recreational waters. These high
levels, given a subsequent amount of time, will die
down, due to “salt water, sun, or age, predation by
other organisms and dilution” (Ocean Water
Protection Program). However, the Surf Riders
Foundation as well as the state of California
recommends that all beach-goers wait a minimum of
seventy-two hours before returning to the water in the
hopes of minimizing time spent in contact with
polluted water while giving the bacteria enough time
to die off or be diluted to levels no longer considered
harmful by state and government regulations.
Almost universally, microbes have been
recommended as a measure of water quality for
recreational waters. Bacteria naturally occur in
water, and while most are not harmful, others,
especially in large quantities, can cause problems.
Indicator bacteria (total coliform, fecal coliform, and
enterococcus) are measured to determine whether the
waters are safe for recreation. Indicator bacteria are
relatively easy to test for and fecal coliform bacteria
outlive most other bacteria. This means that if an
absence of fecal indicator bacteria is found, one can
safely assume that there is an absence of other
potentially dangerous bacteria as well. They are also
good indicators of the “presence of harmful viruses,
bacteria, or protozoa” (Ocean Water Protection
Program). Dwight et al. (2004) found that surfers of
Northern Orange County beaches reported almost
twice as many symptoms of illnesses due to exposure
of polluted recreational water than did surfers of the
less urbanized Santa Cruz area, indicating that
urbanized runoff contains larger quantities of
pathogens. Another study of Avalon Bay, Catalina,
California found that fecal indicator bacteria levels
decreased during the day and hypothesized that the
sunlight may have induced a die-off of the bacteria
(Boehm et al., 2003). Lastly, another study found
that fecal indicator bacteria are evenly distributed
throughout the surf zone because of the wind that
drives the waves up the coast, however large
variability was found between samples (Kim et al.,
2004): meaning that samples collected in the surf
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Saddleback Journal of Biology
Spring 2008