Background: The goal of our project was to design a self-sustaining ecosystem, then test and measure the effects of human impact on the ecosystem. A self-sustaining ecosystem requires several components in order to keep a balanced environment. This means ensuring that the natural chemical cycles embodying the ecosystems flow at a natural rate. We know that energy flows through ecosystems, whilst matter cycles within them. The isolation of each of our levels allows us to record quantitative and qualitative data. Not only do we look for noticeable changes in our environment such as death of fish or heavy mold growth, we also took qualitative evidence through soil and water sampling. This can be seen on our ecocolumn data table. This data can help us determine how much water we add to our ecosystem to ensure a healthy cycling of the environment.
In our ecosystem, we were required to apply our knowledge of the water, carbon, phosphorus, and nitrogen cycle. The water cycle requires energy from the sun, which evaporates water and takes it into the air as a form of water vapor. The gaseous water vapor is then converted into a liquid state as it gathers. This is called condensation. Precipitation is the process of the water travelling back to the earth in liquid form, repeating the water cycle. The carbon cycle represents the circulation of carbon molecules throughout an ecosystem. Carbon is essential as it provides energy for living beings. Carbon is absorbed by plants through photosynthesis. Carbon atoms are then transferred to further trophic levels, providing energy. Carbon returns to the atmosphere through cellular respiration. The nitrogen cycle relies on the use of bacteria to continue the process of nitrification. NO2 is first absorbed from the atmosphere by bacteria or plant roots, which is then converted into ammonium, then NO3. NO3 is the form of nitrogen that living organisms use. Denitrifying bacteria converts the NO3 back to N2 in the environment. The phosphorus cycle, unlike the previous cycles, does not have any form of reservoir in the air. Instead, it is found within rocks. These rocks, when weathered, bring nutrients into the soil which is then absorbed by plants. As consumers eat these plants, they take in this phosphorus. The phosphorus is eventually brought back into the soil by decomposers when the consumer dies, continuing the cycle.
The ecosystem itself consists of three main levels: Terrestrial, decomposition, and aquatic levels. The terrestrial level contained soil, grass, mung beans, and crickets. The decomposition level contained dead leaves, pieces of an apple, pieces of potato, and worms. The aquatic level contained water, 2 elodea plants, three three guppies, sand, and gravel. These levels were stacked up with the terrestrial on the top and the aquatic level on the bottom. This allowed for the most efficient movement of the nutrients towards the aquatic system, providing a better cycling of nutrients.
Introduction: Our problem: Primarily, we had to figure out how can we create the most efficient self-sustaining ecosystem. After that phase was completed, we were observing how eutrophication affects the ecosystem.
Our hypothesis: If we add ammonium nitrate to the ecosystem, thereby exceeding the critical load and activating eutrophication, then the excess nitrate concentration will damage the ecosystem and life within the column will diminish.
Human Impact :
Calculations –
Diagram:
We attempted to make our ecocolumn as stable as possible by limiting the animals/creatures residing in our terrestrial level. Because we chose to limit the number of animals/creatures in our ecocolumn, our ecocolumn’s food web is relatively short. The producers are elodea, bean plants, and the grass. Our top level consumer would be the guppies, which stood as primary consumers. If the fish died, there would be a significant increase in oxygen throughout the ecosystem as the fish were the main consumer of oxygen. Although we do not have a secondary consumer in our ecosystem, if we hypothetically had a secondary consumer consuming over 4,200 kcal, then our primary consumer would consume around 42,000 kcal while the tertiary consumer would have only 420 kcal. This is based on the 10% rule of energy which states that “On average it is estimated that there is only a 10 percent transfer of energy between one trophic level and the next”(biosphere, n.d.). The 90% is lost on waste, cellular respiration and maintaining life for the organism. If the decomposers were removed, we would have less nitrogen, oxygen, and carbon for the plants. This is because the decomposers, which primarily consist of worms, bacterium, and fungi, are able to break down organic material, converting it into nitrogen, oxygen, and carbon for the ecosystem. The loss of this would be tolling for the fish as they require oxygen.
A food web with more species would be more resilient because if one species e.g. primary consumer was removed, its higher level consumers could still rely on other primary consumers for energy. Although the overall energy displacement would change as the web faces a loss of one species, secondary and tertiary consumers would eventually have to rely on other primary consumers for food. This could result in the significant decrease in the population of one primary consumer unless there are other primary consumers to meet the energy requirements of higher-order consumers. Keystone species may be apparent in both food webs, but one with more species could still rely on other primary consumers whereas the loss of a keystone species in a food web with few species would mean a significant change in the food web’s overall structure. Our goal for this project is not only to maintain our ecosystem, but measure and learn how to remediate our ecosystem after human impact.
Results:
During our experiment, mold was first noticed growing within the first week. Although we expected mold, we did not initially place this into the ecocolumn. It was seen as a byproduct of our compost and (rain) water. Another unexpected organism was grass. Because we only added mung beans as our only plant in the terrestrial ecosystem, it came as a huge surprise when we noticed grass also growing. The growth of this could detract from our true results as the grass used nutrients that could’ve been for the mung beans.
Data Analysis:
When we began the lab, both the aquatic and terrestrial ecosystems of our ecocolumn had stable, safe levels of pH, nitrogen, phosphates, chlorine, along with the other nutrients we tested for throughout the course of the lab. Our bean plants and elodea thrived. After a week of initially creating the ecocolumn, we introduced three fish and one snail. Unfortunately, one of our three fish died one day after they were first put in. Within a few weeks after the aquatic organisms were introduced, the levels of minerals and pH approached dangerous levels in the aquatic ecosystem. For example, the Nitrate level started out at 20 ppm, a safe level for freshwater, and jumped to 60 ppm on the third of November. The pH started at a 6.5 and jumped to 8.8 on the tenth of November. We had similar results in the terrestrial ecosystem. The phosphorus levels in the terrestrial ecosystem started at 1 ppm and jumped to 4 ppm on the twenty fourth of November. As a result of the increasing mineral and pH levels in both the terrestrial and aquatic ecosystems, we decided to stop watering our ecocolumn. The water was going through the decomposition and adding an excess amount of nitrogen and phosphates which was disrupting the aquatic ecosystem. By stopping the water flow we were able to keep the mineral levels stable and in some minerals, slightly decrease.
Most of the complications we encountered with our ecocolumn were results of our compost pile. We put pieces of potatoes and apples along with leaf litter and worms. The food pieces created a huge excess of mold which magnified the amount of nitrogen and phosphate in the Aquatic ecosystem. Other natural ecosystems that have an excess of nitrogen or phosphate are affected in a similar way. The water becomes polluted and damages the wildlife living within and around it.
For our human impact, we decided to add ammonium nitrate. This affected our ecocolumn negatively. The mineral levels rose to dangerous levels. Within a week, the Nitrate level rose to 200 ppm, which extremely dangerous level for an aquatic ecosystem. Since Since “excess levels of nitrates in water can create conditions that make it difficult for aquatic insects or fish to survive” (Nitrates and Their Effect on Water Quality, 2014), our human impact led to the death of a snail, a fish, and an elodea plant. The ammonium nitrate was devastating to our ecocolumn.
| TEST DATE | 11/10 (BEFORE Human Impact – addition of Ammonium Nitrate) | 11/19 (AFTER Human Impact) | 11/24 | |||
| pH | 8.8 | 6.6 | 7 | |||
| Temp. (ºC) | 19 | 19 | 20 | |||
| D.O. (ppm) | 6 | 9 | 9 | |||
| Phosphates(ppm) | n/a | 8 | 11 | |||
| Nitrates(ppm) | 160 | 200 | 80 | |||
| Chlorine (ppm) | 0.1 | 1 | 0.5 | |||
| Turbidity | 0.04 | 0.063 | 0.076 | |||
| Odor | 3 | 5 | 5 | |||
| Color | 3 | 4 | 4 | |||
| Aquatic Flora | 2 elodea | 1 elodea | 1 elodea | |||
| Aquatic Fauna | 2 guppies alive, 1 dead guppy. 1 snail alive. | 1 guppie alive | 1 guppie alive |
The Nitrogen Cycle within our ecocolumn:
 |
The Nitrogen cycle starts of with N2; a form of Nitrogen found in the oxygen that is unusable for most organisms. Nitrogen fixing bacteria found on the roots of legumes (Mung beans in our ecocolumn) convert the atmospheric N2 into NH4+ through a process called ammonification. The worms in our compost pile broke down any dead matter and turned into usable Nitrogen. The mold found in our decomposition transformed the Ammonium into Nitrites and Nitrates through a process known as Nitrification. These forms of Nitrogen dropped into the Aquatic ecosystem. |
Conclusion:
Our data supports our hypothesis. We believed that adding ammonium nitrate into our ecocolumn would ultimately damage the ecosystems. Within just days of introducing ammonium nitrate, our snails, fish, beans, and elodea began to deteriorate or die. The increase in mineral levels from the aquatic ecosystem also indicates that the entire ecocolumn was being destroyed. Through this experiment we have learned that too much nutrients and minerals within an ecosystem can be devastating to the wildlife.
Throughout this experiment the water in our eco column began to turn yellow. This is because of a surplus of nitrogen and phosphorous in our ecocolumn. This change showed us that in our ecocolumn whether it be from the terrestrial chamber or the decomposition chamber there was too much nitrogen being produced. This would result in nitrification in the aquatic environment. This would impact our fishes by slowly kill our fish because of the lack of oxygen in the tank. In our decomposition chamber there was a lot of mold growing which meant that there was a lot of nitrogen being produced. This was because of the amount of water we were putting into our ecocolumn the damp environment provided optimal conditions for the nitrifying bacteria to grow.
In some of the ecocolumns in the classroom they had eutrophication in the early stages of their ecocolumn which resulted in the death of many of their organisms early on. These early signs of eutrophication in their ecosystems were probably a result of adding too much water to their ecosystem increasing the rate of nutrient cycling in their ecosystem. Increasing the amount of phosphorous and nitrogen in their ecosystem. Another reason why their ecosystems were unstable might have been because of the addition of fruits to their decomposition chamber. The decomposition of fruits produced the phosphorous which then flowed into the aquatic ecosystem. These things would lead to eutrophication in their ecocolumn resulting in a unstable ecosystem.
Compared to the real ecosystems in the world our ecosystem was very controlled. We were able to control exactly how much water went into the ecosystem, which is something that real ecosystems are not able to do. We also set up our ecosystem putting things in that we hoped would result in a sustaining ecosystem. In real life however, things are not simply put into ecosystems in hopes that the ecosystem can sustain itself. Initially everything in our ecosystem was very controlled compared to the real ecosystems. However, as time went on there was less and less we could control. As our water turned yellow because of the surplus of nitrogen we could not do anything about it other than decrease the water we put into our ecosystem. We could only just hope the ecosystem would fix itself somehow. In the real ecosystems this same thing happens if the ecosystem is introduced to a harmful chemical there is no person that can go in and change something in order to fix it. The ecosystem can only run through its cycles in hopes that it can cleanse itself of this harmful chemical, much like we had to do in our ecocolumn. Our ecosystem was an open system because it was affected by the temperature and we were also able to add water to the system. This affects the ecosystem because factors other than our addition of water or what we initially put into the ecosystem can affect it. The amount of sunlight the ecosystem got would affect the growth of the mung beans which affects the rest of the ecocolumn.
Our information is useful to the community because it shows that adding excess ammonium nitrite much like farmers do to their crops can lead to eutrophication affecting many levels of the ecosystem. It can result in the deterioration of many organisms in the ecosystem. Which would then lead to a deterioration of the ecosystem, resulting in a chain reaction that could then affect ecosystems close by and maybe even farther away. It would be useful to try and research the affects of an overload of ammonium nitrate on a bigger scale. It would also be useful to research the affects of other chemicals that are found in fertilizers or nutrient enrichments that farmers apply to their crops.
In order to decrease the nitrification happening in the aquatic environment, we decided to stop adding water until we made our human impact in our ecocolumn. We did this in hopes that the removal of water would slow the flow of nutrients in our ecocolumn. After we decided to stop adding water to the ecocolumn we saw a standstill in terms of nutrient cycling in the ecosystem. Phosphorous did not increase nor decrease it remained the same after the first test we took after our decision. However, about a week later the phosphorous did increase, we assume from the water that was still present from before. The removal of ‘precipitation’ in our ecosystem did decrease the addition of phosphorous in our aquatic ecosystem. However, nitrates were still increasing in our aquatic ecosystem. So, while the removal of precipitation in our ecosystem, brought the addition of phosphorous in our aquatic environment to somewhat of a standstill, it did not achieve the results we wished it would. It did not necessarily decrease the nutrient cycling throughout our ecosystem, rather it just stopped it for a couple days.
A big source of error within our experiment was with our data collection. We weren’t able to collect data for all components of our table due to lack of materials. We also had to switch testing materials throughout our testing days which could also have caused some skewed numbers. Another source of error was early on we were unsure how much water we should be adding to our ecocolumn and when we should be adding it. There were many times when sometimes we would miss a day adding water. When we would remember to add water however we were always stuck with the problem of how much water we should be adding. We were always unsure how much water our ecosystem needed since it was just in its beginning stages. Our additions always ranged from 30-50mL but this uncertainty may have affected our ecosystem early on. The inconsistency could have affected the nutrient cycling in our ecocolumn. There was also an unexpected growth of grass in our ecocolumn. We are unsure of how the grass got into our terrestrial ecosystem but its presence was unexpected . This growth of grass could have taken energy away from the mung beans. There could have been more mung beans, but instead there was grass.
In this experiment we learned that everything that is added and removed from an ecosystem affects the ecosystem as a whole. There is no such thing as just changing something from one part and not having it affect the entire ecosystem. As an ecosystem continues changing and evolving, so too will the organisms living around it. We must continually adapt to the environment or we will inevitably fall into extinction, unable to assimilate into the changing environment we live in. We realize that although human impact on an environment may benefit us, it can also be harmful to nature. By taking care of what we do to the environment, we can prevent unforeseen negative environmental changes and preserve earth’s natural state.
Citations:
Bernhard, A. (2010) The Nitrogen Cycle: Processes, Players, and Human Impact. Nature
Education Knowledge 3(10):25
biosphere. (2014). In Encyclopædia Britannica. Retrieved November 30, 2014.
Nitrates and Their Effect on Water Quality – A Quick Study. (2014, January 1).
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Phosphorus Cycle. (2008, March 2). Environmental Literacy Council. Retrieved November 30,
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Reece, J. B. (2014). Campbell biology. Boston, MA: Pearson Learning Solutions.
Our Ecocolumn Project! 