Water Quality at Doheny State Beach
Kim Chené, Brittany Harding
Department of Biological Science
Saddleback College
Mission Viejo, CA 92692
Escherichia coli is prevalent in the top layer of sand at some of the area's most
popular beaches, even when the surrounding ocean water tested "clean". By studying the
water bacteriology of a specific oceanic community, an investigator can determine if that
community is affected by differing levels of bacteria in its environment. All hillside runoff
most likely contains coliform bacteria, more specifically Escherichia coli. Testing for E. coli
is necessary, as all coli forms may be suppressed by high populations of other organisms.
Indicators of pollution include algal blooms, lichens, erotological forms of diatoms;
coliform bacteria, “sewage worms,” in addition to the more obvious signs of contamination,
such as flu symptoms in humans or disorientation in marine mammals. Three points were
selected for the collection water samples at Doheny State Beach in Dana Point, California.
The first sample was 100 meters directly west (toward the ocean) to the storm run-off; the
second, south 100 meters (along the beach); and the third, 100 meters north (along the
harbor). The samples were tested for the presence of coli form bacteria. The presence of
gas or acids in the tubes after the incubation period indicated the presence of coliform
bacteria in the sample. The most probable number (MPN) was then calculated in order to
determine the concentration of coliform organisms at each location. The investigators
hypothesized that there would be a great difference between each point that the samples
were taken. However, An ANOVA of the means yields p > 0.05 (0.27812). There is no
difference between the means; thus, coliform bacteria concentration is equivalent in all
three locations.
Introduction
Certain elements that are introduced to the beaches of Southern California are extremely
harmful to the marine life and its surrounding environment. Such elements are often referred to
as pollution. If severe, water pollution can kill large numbers of fish, birds, and other animals, in
some cases killing all members of a species in an affected area. Not only will it affect those
living in and around that area, but will also affect anyone or thing that is introduced to the water
or an organism from that area. Pollution makes streams, lakes, and coastal waters unpleasant to
look at, to smell, and to swim in. Fish and shellfish harvested from polluted waters may be
unsafe to eat. People who ingest polluted water can become ill, and, with prolonged exposure,
may develop cancers or bear children with birth defects (Hart 2008). Several studies have
concluded that it is not only unsafe for humans to submerge themselves in such water, but in
some cases it is known to be lethal. Individuals who swam in areas adjacent to flowing storm
drains were fifty percent more likely to develop a variety of symptoms than those who swam
further away from the same drain (Osborne 2004). Unfortunately, among these fatalities, the
largest grouping was children under five years because their immune systems are less developed
than that of individuals over five years of age and growing bodies take in substances more
rapidly than do mature ones (Lear and Lewis 2008).
Another obstacle for public health is the chlorine used to treat public water, which can
turn into chloroform when it mixes with other materials in the water, which may increase the risk
of miscarriage and poor fetal growth. Many petroleum products are poisonous if ingested by
animals, and spilled oil damages the feathers of birds or the fur of animals, often causing death.
In addition, spilled oil may be contaminated with other harmful substances, such as
polychlorinated biphenyls (PCBs) (Hart 2008).
Whether they enter the ocean by raining out of the atmosphere, running off the land in
streams and rivers, or by coming directly from industrial or municipal sources, large amounts of
pollutants generated by modern society end up in the sea. Chemicals used to kill unwanted
animals and plants, for instance on farms or in suburban yards, may be collected by rainwater
runoff and carried into streams, especially if these substances are applied too lavishly. Some of
these chemicals are biodegradable and quickly decay into harmless or less harmful forms, while
others are non-biodegradable and remain dangerous for a long time.
When animals consume plants that have been treated with certain non-biodegradable
chemicals, such as chlordane and dichlorodiphenyltrichloroethane (DDT), these chemicals are
absorbed into the tissues or organs of the animals. When other animals feed on these
contaminated animals, the chemicals are passed up the food chain. With each step up the food
chain, the concentration of the pollutant increases. This process is called biomagnifications or
bioaccumulation (Hart 2008).
What seems to be the most talked about health threat today is a pathogen that is water
borne and also lies within several of our food items known as E. coli. The correct term,
Escherichia coli, is a common type of bacteria that can get into food, like beef and vegetables. If
the water that people or animals and plants are exposed to contains any human waste, it can carry
the E. coli bacteria. Someone who has E. coli infection may have these symptoms: bad stomach
cramps and belly pain, vomiting, diarrhea, sometimes with blood in it. One strain of E. coli was
found in fresh spinach in 2006 and some fast-food hamburgers in 1993 (Nichols 2008). Beef can
contain E. coli because the bacteria often infect cattle. It can be in meat that comes from cattle
and it's also in their feces. This can occur if the manure is used for fertilizer (a common practice
to help crops grow) or if water contaminated with E. coli is used to irrigate the crops.
Investigators decided to test the water quality at the popular beach in Southern California
named Doheny State Beach. A total of thirty sample bottles of water were collected from the
coast. Ten were collected from 100 meters south of Salt Creek, which runs directly into the
ocean water at the beach, then ten more were taken from the direct line of the creek to the ocean,
and another ten were taken from 100 meters north of the creek. Investigators hypothesized that
there would be a great difference in fomenters and gas producers between the locations of the
samples taken. E. coli, which is found in large numbers in the feces of all animals, lives longer in
water than most intestinal pathogens do. Therefore, if no E. coli are present, there should be no
intestinal pathogens present in the water sample. This is why testing for coliform organisms are
performed as a daily ritual by water departments and waste-water (sewage) treatment plants. It is
regularly tested for in coastal sea water samples, as well as runoff water. The first bacterial test is
a screening test to sample water for the presence of coliform organisms. A series of lactose
fermentation tubes are inoculated with the water sample. If the presumptive test is negative, no
further testing is performed, and the water source is considered microbiologically safe. If,
however, any tube in the series shows acid and gas, the water is considered unsafe and the
confirmed test is performed on the tube displaying a positive reaction. The presumptive test is
also designed to estimate the concentration of coliform organisms, called the most probably
number (MPN) in the water sample.
Materials & Methods
Thirty water samples were collected on the night of October 25th, 2009 at 9:30 pm during
the high tide of Doheny State Beach. Ten sample bottles were filled at 100 meters South and
North of the San Juan Creek as well as another ten collected in the direct line from the creek to
the ocean. Each bottle was then labeled using a grease pencil to indicate what number the sample
was and whether the sample was from the North, South or the “Middle” which was the direct line
form the creek to the ocean. Ten milliliters of every sample was placed into three, triple strength
lactose tubes, 1 ml of each sample into three regular strength lactose tubes, and 0.1 ml in three
more regular strength lactose tubes. Each tube was then labeled using a grease pencil to note the
number of the sample, the amount of sample water included, as well as whether it was triple or
single strength lactose. The tubes were incubated at about 40̊ C for twenty-four hours. After the
incubation period, investigator were then able to record the results. The presence of gas or acids
in the tubes after the incubation period indicates the presence of coliform bacteria in the sample.
The way to tell if there is gas in the incubated tubes is to look to see if there was layer of bubbles
atop the sample. If the bubbles were present then obviously the water sample held bacteria that
formed gasses. To tell if the sample held any bacteria causing fermentation, the water sample in
the incubated tube would turn a distinct yellow color from its original green color before the
incubation process. The most probable number (MPN) was then calculated in order to determine
the concentration of coliform organisms at each location.
Results
Water samples were collected from a midpoint at Doheny State Beach, and from onehundred meters north of that point, and one-hundred meters south. The MPN was calculated
from each of the test tubes, and the mean MPN was calculated for each location. The North
mean MPN was 1018; Middle mean MPN was 1124; South mean MPN was 591.2. A singlefactor ANOVA test was conducted to compare the means. The ANOVA is appropriate because it
compares more than two means at once and yields one p-value for the means, collectively. There
was no difference; a Bonferroni Correction will not be needed.
1600
1400
Mean MPN
1200
1000
North
Mouth
800
South
600
400
200
0
Locations
Figure 1: MPN, or the most probable number index, is used as a measure of the amount of
coliform bacteria present in a sample of water. The locations were chosen one-hundred meters
from each other, North, representing the mean of the samples taken one-hundred meters north
from the Middle location, and South representing one-hundred meters south from the middle
location. An ANOVA of the means yields p > 0.05 (0.27812). There is no difference between the
means; thus, coliform bacteria concentration is equivalent in all three locations.
Discussion
The results of the presumptive test were expected to be different for each location. After
incubation, a reaction was observed in each of the triple strength tubes, and in one-hundred
twenty-seven out of the one-hundred eighty single strength tubes. However, a portion of the
South single strength samples were put into a separate incubator, and incubated at a much higher
temperature, which could account for the large difference between the mean MPN of the South
when compared to the other two measures. Regardless of the source of error, coliform bacteria,
likely including enteric pathogens, are present in the water at Doheny State Beach. An ANOVA
was used to compare the means of the three different locations. The resulting p-value showed
that there was no difference between the bacterial concentrations of the three locations. Thus, the
initial hypothesis was proved wrong. According to the results, there is an abundance of bacteria
spread equally throughout the beach.
Consumption and recreational use of the water at Doheny State Beach is not advised. In
addition to being unsafe for human consumption, the poor quality of the observed water samples
may indicate severe alterations beneath the surface. A high-traffic area, Doheny is prone to runoff from deforestation, including roadwork, development of residential areas, and other
disturbances that aid in ecological change. These changes often favor introduced species over
indigenous or “native” organisms at all levels of biological organization and can result in
changes in microbial diversity, including the introduction of new or increased numbers of
pathogens and indicator organisms (Osborne 2008).
Pollution at this location could easily be controlled by implementing more trees at the
waterway to block sediment runoff from streams into the ocean, less use of fertilizers and other
nutrients that promote plant growth, and careful clean-up of road construction. United States
legislation proposed the cleaning up of sewage treatment plants and industries that discharge
pollutants into waterways (Clean Water Act 1977); but other sources of contamination are still
present, such as sulfur dioxide from power plants, garbage in landfills, and other nonpoint
sources. (Hart 2008) These contaminants which accumulate in the air and reach the ocean
through precipitation are harder to control.
Acknowledgments
Investigators thank Professor Steve Teh for not only his help but his coordination for all
of the materials we needed. We also thank Vince Fiorentino for helping us to collect the water
samples despite that fact that is was extremely cold and at night; thanks for getting wet!
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