The Difference
between Bacterial
Film and
Oil Sheen in
Milkhouse Creek
John
M. Brown, Department of Earth Sciences,
Bacteria in
the water in the Dog River Watershed are very common phenomena. The
bacteria
can often have a rainbow color, a color that is commonly associated
with oil
sheen that is seen in a parking lot after rainfall. The purpose of this
research is to educate the general public on how to tell the difference
between
oil sheens and bacterial film. The methods of research included library
and
internet research, sampling of algae, bacteria and oil in Dog River
Watershed
streams and microscopic analysis of bacterial film. The end result of
this
research is to make people more aware of bacteria and inform them on
how to
know whether what they observe is harmful or not.
Keyword:
Bacteria, Oil Sheen, Film
Introduction
When looking at oil on water, such
as an oil slick in a parking lot, one cannot help but notice the shiny,
rainbow
like color that appears, as well as the film that it makes over the
area it
covers. There have been incidents of oil being in the water within the
Dig
River Watershed. Like the above stated, the oil gives a shiny
appearance on the
surface. This oil gets in the water from runoff on streets, leaks in
vehicle
engines and from parking lots where oil collects. Oil in water can have
a
negative effect on aquatic vegetation, fish and other characteristics
of stream
health (Burger 1997). It can cover leaves on vegetation, which inhibits
photosynthesis and it is a potential danger for any wildlife that may
consume
these plants. Oil in water also has the potential to cause harm to
humans
(Adopt Your Watershed 2003). It can cause drinking water pollution and
make
water dangerous for swimming. There are cases where people have put oil
in
water to kill mosquitoes. This is illegal, even if it is on private
property
(West Nile Virus, 2004). Oil also has a tendency to give an odor
reminiscent of
a gas station (Adopt Your Watershed 2003). This odor is especially
prevalent in
marinas. Engines that have oil in the fuel, such as 2-cycle engines,
leave oil
sheen in the water from their exhaust (Powerboating
2004).
Research Question
The question I am
attempting to answer
is “what are the differences between bacterial film and oil sheen?” How
do
bacteria enter and benefit a stream? The Alabama Department of
Environmental
Management (ADEM) states that there have been several confusing reports
on
sheens made to their
Methods
To
effectively answer the question on the difference between bacterial
film and
oil sheen in the Dog River Watershed, this research focused on a site
on Milkhouse Creek beside
Time was also spent in the
The research site chosen on Milkhouse Creek contained areas that exhibit surface sheens that have the characteristics of oil. To determine if the sheen is in fact bacteria and not oil, a simple test was employed. After locating a shiny sheen on the surface of the water (Fig. 2), the sheen was then disturbed by moving a twig through it. The results of this test will immediately tell if the sheen is a bacterial film or oil sheen.
Results
More times
than not, the sheen that appears to be oil on the surface of the water
is the
result of the natural bacterial breakdown of organic matter (The
Resource, p.1,
2004). When the twig was passed through the sheen it broke into several
fragments. These fragments failed to return to their original form as a
complete sheen (Fig. 3). This is evidence that
the sheen was bacterial film and
not oil. When passing a foreign object through an
oil
sheen, the sheen will immediately return to its original state. There
was also
the absence of any kind of petroleum odor, which is an indicator of oil
pollution. Decaying vegetation also gives off a “rotten egg” odor,
which is
hydrogen sulfide gas (H2S). This gas is the natural byproduct of
organic
decomposition in wet environments and is harmless (The Resource, 2004).
The
bacterial film was surrounded by natural vegetation and there were also
several
places in the creek where dead leaves and other sorts of vegetation were present, which is why the bacterial film
forms. The
bacterial film is harmless to the environment and there is no reason to
call
ADEM (Table 1).
Bacteria enter the water through the surrounding
soil. The
soil is a vast plethora of micro-organisms going through a myriad of
activities. Some decompose the wastes of man and animals and the
tissues of
plants. Some provide nutrients essential to plant life and others
destroy these
nutrients. Certain types of bacteria invade the tissue of living plants
and
animals with some beneficial results (Gordon, 1968). More specifically,
the
bacteria can be referred to as part of the soil biota. Soil biota is
the
biologically active “powerhouse” of soil. Along with bacteria, the
biota is
made up of fungi, algae, earthworms, protozoa, nematodes, mites and
several
other organisms. All of these play a part in the breaking down of
organic
matter. The larger organisms break down the larger organic matter and
make it
available to the smaller organisms. This process is called the “food
web of
soil biota.” For example, earthworms and millipedes shred dead leaves
and
residue and make it available to immobile bacteria. The biota is found
in the
upper few inches of the soil. The smallest organisms in the biota are
microscopic bacteria and fungi and they make up the bulk of the biota.
The
microscopic organisms finish the process of decomposition by breaking
down the
remaining material of organic matter and store its energy and nutrients
in
their cells. When the bacteria die, these nutrients are released into
the
surrounding area. This promotes the growth of other aquatic plants.
Some biota
can even break down pesticides and pollutants. Without bacteria, the
decomposition of organic material would be significantly slower and
there would
be a vast amount of leaves, twigs and other organic material covering
the earth
and important nutrients would not be accessible to other plants
(Rangeland Soil
Quality, Sheet 8, 2001). Bacteria help keep organic debris amounts in
streams low, otherwise streams would be
congested due to the huge
amount of organic debris in the water.
The microscopic analysis of the bacterial film
contained
visible bacterial cells within the sheen. This indicated that the sheen
was in
fact bacteria and not oil.
Conclusion
Bacterial film from
organic decay
in Milkhouse creek shows no threat to
water quality.
In fact, it is good that it is there. The test is very easy to execute
and does
not require any expensive, sophisticated scientific equipment. Any oil
one
might find in the Dog River Watershed is most likely to be around a
marina. The
importance of this research is to educate the public and to make an
effort to
prevent people from reporting oil to ADEM. By using this data, the
general
public should have a firm understanding on how to determine the
difference
between bacteria and oil sheens and the effects oil can have on the
watershed
and the surrounding environment.
References Cited
Adopt Your Watershed. EPA.
2003.
<http://www.epa.gov/
adopt/patch/html/streamins.html> Accessed:
Burger, Joanna. Oil
Spills. 1997.
Davies, Jim. Personal
Interview.
Gasoline Engines: Two Cycle.
<http://powerboat.about.com/library/weekly/aa012303b.htm?terms=2+cycle+engines>
Accessed:
Rangeland Soil Quality - Soil
Bacteria.
USDA, Natural Resources Conservation Service, Sheet 8. 2001.
<http://soils.usda.gov/sqi/files/RSQIS8.pdf>
Accessed:
The Resource. A
Publication of the City of North Augusta Stormwater
Management Department. 2004. <http://www.northaugusta.net?Dept_Serv/Engin_PublicWorks/Stormwater/newssspring04.pdf>
Accessed:
Gordon, Ruth E. The Ecology of Soil Bacteria: An
International Symposium –The Taxonomy of Soil
Bacteria. 1968. p. 293.
