Pond Ecosystem Report

The experimental pond ecosystem was polluted with oil to see what the effects would be. Every week our team added three drops of Pennzoil 5w/30 to our experimental pond ecosystem. We took a count of living

organisms from our control and experimental groups at two different levels to see what effect the oil had on them. The results were dramatic on the upper level of our experimental pond ecosystem. Many if not most of the living organisms were destroyed, while the lower level was somewhat less impacted. The experimental pond ecosystem showed that pollution by oil is mainly limited to the upper portion of the ecosystem itself. The cause for this unusual circumstance is because of the hydrophobic property of the oil.


The ideas of pollution in our ponds and lakes are all to real in this day and age. Even in Alaska our streams and lakes are polluted to some degree. The Alaska Department of Natural Resources (2007) has reported that fecal coli-form bacteria, sediment, and petroleum products are the primary source of pollutants of the surface waters in Alaska.

With man made natural disasters such as the oil spill of the Exxon Valdez in 1989, our environment has sustained major damage. This accident alone killed many animals and destroyed the natural ecosystem of the region. Greenpeace (2001) has reported that 250,000 to 500,000 sea animals died immediately, not to mention billions of salmon and herring eggs. The effects of the spill are still being felt with lower birth rates and stunted growth of nearly all of the animals impacted. The University of North Carolina (2002) has found that the effects of the Exxon Valdez oil spill are lasting longer than expected. The team estimates that some shoreline habitats may take another thirty years to recover.

Before we go any further we should learn a little about what a pond ecosystem is. According to Wikipedia (2006), a pond ecosystem is a specific type of fresh water ecosystem that is largely based on autotroph algae which provide the base trophic level for all life in the area. The largest predator in a pond ecosystem will normally be a fish and in between ranges smaller insects and microorganisms. It may have a scale of organisms from small bacteria to larger creatures.

Aquatic ecosystems perform many important environmental functions. For example, they recycle nutrients, purify water, ease flooding, and provide habitats for wildlife. Mini Pond (2004) reports that a pond ecosystem degrades when the ecosystem’s ability to absorb stress has been exceeded. A stress on these ecosystems can be the result of physical, chemical, or biological alterations to the environment.

Usually in the pond ecosystem there are two types of organisms. The first is called Autotrophic. These organisms are the producers that generate organic compounds from inorganic material. Algae use solar energy to generate biomass from carbon dioxide and are the most important autotrophic organisms in an aquatic environment. The second type of organism is referred to as Heterotrophic. These are the organisms that consume autotrophic organisms and use the organic compounds in their bodies as an energy source.

Our group thought it would be interesting as well as educational to see first hand what the effects of motor oil in a pond ecosystem would have. We believe that the motor oil will have a detrimental effect on the pond ecosystem. We also believe that the upper levels consisting of the algae and Cyan bacteria will be most affected since they are near the top and oil has hydrophobic relationship with water. We do not believe that the organisms in the lower portions of the ecosystem will be impacted as much because the oil will have a harder time reaching them. We also believe that given enough time that the ecosystem as a whole will die due to the lack of algae.

Materials and Methods:

The material we used in this experiment consists of living organisms and their food stuff. First, I will list the organisms, followed by the amount of food. We used half a pipette for the living organisms and the five milliliter rule for the food. They are as follows. Gloetrichia, Oscillatoria, Anabaena, Chilonas, Paramecium Caudatum, Stentor, and a few drops of Amoeba. The addition of food is as follows; 5g Mgso4 solution, 15g KH2PO4 solution, 10g K2HPO4 solution, 2.5g NaCI solution, 2.5g NaNO3 solution and 2.5g CaCI solution. These materials were added to two separate two liter glass containers filled with purified water and a measured scoop of dirt and gravel respectively. We then labeled each of the two glass jars, one control and the other experiment. During the four week period we introduced Pennzoil 5w/30 to our experimental group once a week using three drops from a dropper. We were careful not to disturb the water as we put the oil in because we did not want the oil to mix, but instead stay on top of the ecosystem.

After our first week, we started collecting data from our pond ecosystem. We did this by taking samples with a dropper from the upper and lower regions of the control and the experimental groups. We made wet mount slides of each region and looked at them with the microscopes provided by the laboratory. The process we did for counting the organisms was a simple yet affective approach. We used the field of view approach that is noted in our Introductory Biology Lab book (2007). The book states that you have one field of view per slide. Within this field of view there are five points of interest; top left, top right, middle, bottom left, and bottom right. With the microscope set at 45X, we went to each of the points of interest and did a count of all living organisms. We did this weekly for the control group as well as the experimental group.


The results of our pond ecosystem experiment did produce some unusual findings. This may be the direct result of contamination that happened during the first week or to other factors that are unknown. The first graph reveals the results of counting the top layer of the control group. As you can see the Chilomonas were very productive after one week of being in the ecosystem. Likewise, the Amoeba’s were proficient in the second week. By the end of the fourth week all organisms excluding the Oscillatoria had declined.

The next slide shows the four week results of the bottom level of the control group. All of the organisms in this group seemed to enjoy a steady increase of offspring. The counts during the fourth week indicate that the Paramecium’s were having a population explosion.

The next sets of graphs are from the experimental group. If you remember our experimental ecosystem had 3 drops of oil introduced each week after the first week. As you can see the Oscillatoria and Chilomonas seem to have had a strong growth in population, but by week three everything seemed to be dead or greatly reduced.

The last graph shows the bottom count for the experimental ecosystem. As you can see, there was dramatic growth in the second week by the Chilomonas as well as the Oscillatoria. This may be due in fact to an incident of contamination that we will discuss later. By the third week, everything seems to have returned to normal except for the rapid growth of the Stentor group.


Now that the experiment is over I would like to discuss some of the findings our group came up with. By looking at the graph for the experimental upper level versus the control upper level, one can clearly see that the oil had a negative effect on all of the living organisms in this region. Likewise, the experimental bottom level compared to the control bottom level shows a somewhat lesser amount of organisms. This could be caused by two factors, either the oil was penetrating to the lower level or the organisms were running out of food to consume due to the pollution of the oil on the surface of the ecosystem. Either way, it is clear that oil in the pond ecosystem has an overall effect of pollution causing death.

One factor that may explain the substantial rise of organisms in our experimental ecosystem during the second week, was the inadvertent addition of Tetra Fauna Reptoman fish food on October 12, 2007 by a participant in another study. The contents of the fish food are as follows: 42.5% crude protein, 8.5% crude fat, 2% fiber, 8% moisture, 1.8% phosphorus, 25mg calcium and 100mg ascorbic acid. One can tell by comparing the charts from the control and experimental groups that the fish food had a rather dramatic effect on some of the organisms causing a population burst of sorts. In the end, the growth spurt was short lived and the oil had an even more profound effect on the experimental ecosystem.

After some debate by my colleagues and me we came to the conclusion that our experimental design should have included the mixing of the oil with the water in the experimental ecosystem. We feel that this would be more representative of what would happen in the natural world.

I believe this experiment, even with the introduction of the fish food, was a success. The data clearly shows that the introduction of the motor oil had a detrimental effect on the microorganisms that lived in our experimental group, more so on the upper level than the lower level. I would have to conclude that our original hypothesis was correct.

Works Cited:

Alaska Department of natural Resources, division of mining, land and water. (2007). Retrieved on 10/05/2007, from http://dnr.state.ak.us.
Greenpeace, The Exxon Valdez oil spill fifteen years later. (2004) Retrieved on 10/22/2007, from http://www.greenpeace.org.
Mini-Ponds. To investigate diversity in a pond water ecosystem. (2004). Retrieved on 10/15/2007, from http://www.science-class.net.
University of Anchorage Alaska, (2007). Introductory Biology lab book, wet mount micro-slide. Pg. PE4.
Wikipedia. (2004) Aquatic Organisms. Retrieved on 11/25/2007, from http://en.wikipedia.org/wiki/Aquatic_ecosystem.

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