Lab Report: Biomagnification and Bioaccumulation of DDT

Abstract

This lab experiment simulates the processes of bioaccumulation and biomagnification using a model of a food chain in a lake ecosystem. DDT contamination is represented by M&M candies, and the experiment demonstrates how DDT accumulates and magnifies as it moves up the food chain.

The results show a significant increase in DDT concentration in higher trophic levels, illustrating the environmental impact of fat-soluble pollutants like DDT. The lab also highlights the concept of energy transfer and the 10% rule, where energy decreases as it moves up the food chain. The observations confirm the theoretical understanding of these ecological concepts.

Objectives

1. Visualize the processes of bioaccumulation and biomagnification.
2. Distinguish between the similar concepts of bioaccumulation and biomagnification using a mathematical model.
3. Calculate the amount of energy gained/lost through the energy transfers of a typical food chain.
4. Review trophic level names and energy characteristics.

Background

DDT was the first synthesized insect pesticide that was widely used throughout the globe after the WW II.

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In the case of numerous African nations, this pesticide proved its soaring popularity due to its primordial ability to fend off disease-carrying mosquitoes. While it still does not change the fact that mosquitoes posed a noteworthy threat to the globe’s health, the situations regarding the contagious Malaria flu reached its peak in African nations.

Therefore, naturally, people began to use this pesticide in order to kill off all the mosquitoes within the vicinity of their respective habitats. However, chaotic consequences ensued. The organisms in the numerous African ecosystems began to assimilate toxic substances into their bodies, resulting in greater environmental harm along with enhanced pollutions.

One dominant example would be birds. Most species of birds need numerous substantial provisions of calcium in order to lay healthy eggs. However, because of the growing amount of toxins, the eggs won’t hatch properly. And, even if it does, the baby birds will either live to see the next sunrise before their deaths or die immediately. This caused a sharp population decline for bird species such as Osprey, Brown Pelicans, and Bald Eagles. Fortunately, the American government recognized the potential threat of this pesticide relatively early, responding by banning the commercial use of this organochlorine pesticide. In order to prevent this situation from blooming into a full-scale crisis, the Stockholm Convention on Persistent Organic Pollutants (POPs) was introduced at the Conference of Plenipotentiaries to try and eliminate and/or control the use of DDT and other POPs around the world. This convention received over 150 countries’ consensus, thus banning the use of DDT at all costs.

Materials and Procedure

Materials

The lab materials included M&M candies, cups representing different trophic levels, and instructions for transferring M&Ms between cups to simulate the movement of DDT through the food chain.

Procedure

The pile of M&M’s represents the phytoplankton population in a lake. The printed “M” on the candy represents the amount of DDT (in ppm) the algae ingested from pesticide runoff from a nearby agricultural area. There are 100 M&M’s in the pile. Each circle below represents on phytoplankton. Mark the amount of toxin each phytoplankton has ingested. If there is a full “M” stamped on the candy then that phytoplankton has ingested 1 ppm of DDT, so write “1” in one of the circles below. If there is no “M” on the candy then that phytoplankton did not ingest any DDT so write a “O” in one of the circles below. If there is a partial “M” on the candy then estimate how much of the “M” there is. For example, if there is only on hump of the “M” then that would equal ½ a unit of DDT ingested by that phytoplankton so you would fill in one of the circles below with ½. Zooplankton in the lake (population size 20) each eat 5 algae. Move 5 M&M’s into each of the zooplankton cups. Record the amount of DDT each zooplankton has ingested using the instructions from step 1. Write these amounts onto the individual copepod pictures below. Minnows (population size 5) in the lake each eat 4 zooplankton, ingesting energy and the toxin that is stored in the zooplankton as well. Move the correct number of M&M’s from the zooplankton cups into the minnows cups. Record the amount of DDT ingested by each of the small fish onto the fish below using the instructions from step 1 to calculate the total amount of each fish. Two eels then come along for dinner. One eels eats 2 minnows and the other eel eats 3 minnows. Move the correct number of M&M’s from the minnow cups into the eel cups. Write the amount of DDT ingested by the each eel onto the pictures below. Use the instructions from step 1 to calculate the total amount of DDT for each. Finally, an osprey flies by and eats both eels. Move the correct number of M&M’s from the eel cups into the osprey bowl. Calculate and then write the total amount of DDT ingested by the osprey onto the picture below.

Processing with Tables

Table 1: DDT Ingestion and Energy Content by Species

Table 2: Total Energy Content by Trophic Level

The above tables represent the total sets of data that I have gathered during my lab. Disregarding the semi-tables that display the process of calculations, the first column of my table depicts the average amount of DDT ingestion for each and every species. Since I knew the formula to get the said data, I was able to process this column with comparably more ease than the other ones. The second column depicts the amount of energy for one species under each category. For example, only one phytoplankton contains 200 kcal within its body. Likewise, that column of my table depicts the amount of energy that each individual of the species have within their bodies. The next column, column C, shows the total amount of energy for each and every categories through kcal. For instance, there are 100 phytoplanktons in the lake. Each phytoplankton contains 200 kcal of energy within their bodies. Therefore, if you multiply 200 with 100, you get the total amount of energy which is 20000. The last column basically illustrates the name of the trophic level the species belong in this lab. You can see that the phytoplanktons, which are a type of green algae, is the primary produce that supports that entire ecosystem through its ability of photosynthesis. Next, you can see that copepods are the primary producers, or herbivore, that eat the phytoplanktons. The copepods are eaten by a small fish known as the minnows, and they mark the place of the secondary consumers. Next, the eels come as tertiary consumers due to their predation on the minnows. However, the top, or quaternary, consumer would be the osprey in this case. Osprey feeds on eels, and there are no other predators that hunt ospreys in this lab.

Data Analysis

Summary of Data Trends

The amount of DDT found in the osprey with the amount found in one phytoplankton are vastly different to say the very least. In phytoplankton, the average amount of consumed DDT is about 0.28 ppm. This contrasts greatly to the one measured from the osprey, for they have the total amount of 28 ppm of DDT ingested within its body. While it still does not change the fact that phytoplanktons are the ones who directly consume DDT from their surrounding environment, it is surprising to note that the actual amount of toxins are far less than those of one osprey. The calculations reveal that one osprey have about 10 times more ppm of DDT inside its body than one phytoplankton. This is due to the process of biomagnification, which states that as the predation progresses higher up in the food chain, the amount of absorbed toxins will only augment.

First, there are three drawn pyramids: Energy, Typical, and Number. Energy pyramid basically depicts the flow of energy through the food chain using indicative arrows. This will contribute in displaying how the energy is lost and gained as the predation commences. It is obviously important to know the concept of energy pyramid, for it complements the theory that states that the majority of the gained energy is lost in order to maintain metabolism for most of the organisms. Number pyramid depicts the number of each organisms per trophic level. This pyramid is quite interesting because this pyramid is the only one showing the estimated quantity of the organisms in an ecosystem. Notice how many phytoplanktons are required to maintain and feed one osprey. Likewise, there has to be producers of vastly greater numbers in order to sustain only a few of the top consumers. Not only that, but the number of organisms shows a significant decline as the trophic level progresses, proving the fact that each trophic level requires more of its previous trophic level to maintain its population as a whole. A typical ecological pyramid shows the most fundamental relationships through the depiction of a food chain. All it shows are the designated trophic levels such as the producer, primary consumer, secondary consumer, and so on. The shapes of the pyramid are usually a triangle. This shapes pretty much works for nearly all the cases. and I believe the shapes depicted by the three pyramids do make sense. To specify, the triangle becomes steeper and narrower as the trophic level progresses. Numerically and diagrammatically, the shape of a triangle will be fit to satisfy all three food pyramids.

Observation

During the data that I have collected, a clear augmentation of the amount of toxins are easy to recognize throughout. This is because of the process known as the biomagnification. As you can see from the table, the amount of absorbed toxins are continuously increasing through additional trophic levels. This undoubtedly demonstrates the said theory while illuminating the fact that DDT is a fat-soluble pollutant, therefore proving it impossibly difficult to secret through waste. My observations state that the amount of acquired energy are dwindling as the trophic level progresses. This is clearly due to the 10% rule, which states that the existing trophic level will only be able to obtain only the 10% of the energy previously obtained by its predecessor. This is due to the fact that energy, once gathered, are extremely expendable by variety of methods. The organisms tend to use most of its gathered energies before being consumed by its predators, therefore bequeathing only a few percentage of its primary energy. With that said, notice how the osprey, the top dog of the food chain, received the most toxin with the least energy.

Conclusion

In conclusion, I have learned that the process of biomagnification along with accumulation can have a dramatic impact on an ecosystem as a whole. Since this lab primarily deemed DDT as the pesticide at hand, I was also able to read the briefed version of its history while understanding the harmful effects it has on the ecosystems and the organisms as a whole. Furthermore, I was also acquainted with a few conceptions in regards to calculating the total energy while at the same time applying the 10% rule for the energy reductions. It was a very worthwhile experience to know how much of a real-world problem these chemical regulations are as well as the everlasting impacts of the fat-soluble pollutants that continue to plague numerous ecosystems even today. Not only that, I learned to visualize the processes of bioaccumulation and magnification while being able to distinguish between the two using both scientific and mathematical models. Finally, even though I am already familiar with this concept, it was quite refreshing to bring in the names and levels of trophic levels into this lab. I was able to connect the said knowledge directly to the topic that I am dealing right now. With that said, I believe I have gathered more than sufficient information that would aid me in the future regarding the concepts of biomagnification and accumulation.

Evaluation

Overall, this was a decent lab that served its purpose of demonstrating the concepts regarding the process of bioaccumulation along with magnification. The lab provided sufficient background information, and the procedures were concise and easy to understand. However, I would like to make it clear that this lab could’ve been more productive and exciting if made online and virtual. Due to the fact that this activity was error-sensitive, the lab itself was very emotionally-provocative. I personally made one big error in regards to counting, and my group was forced to redo the whole counting again in the hopes of getting it finally correct. Frustrated would be the least of what I truly felt during the process of redoing. Therefore, this lab could’ve been shaped into a much better activity if I get to do it with my laptop. This will surely save a lot of time while at the same time be a bit less annoying and tedious. Furthermore, doing this lab on a computer will also grant anyone an easier access to Google Drive or any means of recording medium. Through these basic amenities, I could always jot down things that compose my lab report there and then. Doing this entire lab physically with all the tokens and bowls will be troublesome to say the least. It would be way better if this lab was translated electronically onto a computer.