M&M Biomagnification Lab 2023

Biomagnification Through a Food Chain Purpose: You will use M&M candies to model bioaccumulation and biomagnification through a food chain. In this simulation, you will follow a toxin through a food chain and calculate the average amount of toxin at each trophic level. Then you will use the data collected to calculate the amount of energy acquired per organism and the total amount of energy per trophic level. Since the concepts of bioaccumulation and biomagnification (or biological magnification) are similar, they are often confused for one another. Bioaccumulation is the increase in the concentration of a fat-soluble toxin within the tissues of individual organisms; Biomagnification describes the increase of that toxin up through a food chain. Most organisms are capable of eliminating water soluble toxins through the liver and kidneys, but fat soluble toxins get stored within the tissues and organs long term. If organisms containing fat soluble toxins get eaten, the consumer (and whatever consumes it) will ingest the stored toxins as well, leading to a magnification of the toxin higher up the food chain. Higher order consumers, like bald eagles and other birds-of-prey, are especially vulnerable to the effects of biomagnification. This activity will demonstrate the concepts of bioaccumulation and biomagnifications using the classic example of DDT, as well as review how energy is transferred through a food chain. Background: Shortly after WWII, a new super-pesticide was put into widespread use across the United States. Dichloro-diphenyl—trichloroethane (DDT) , the first synthetic pesticide, had been used with massive success during World War II to combat malaria and other diseases carried by insects. In the baby boom period right after the war, this new technology was called upon to help keep America’s agriculture healthy and prosperous and American families’ housed in idyllic abodes free of insects. No one knew that they were actually unleashing one of the most persistent chemicals commercially available. Not until Rachel Carson’s 1962 book Silent Spring did people start to question this chemical and the unforeseen negative effects it was having on the environment. Carson’s book outlined how DDT stayed within a food chain, building in toxicity as it was passed in the tissues from one trophic level to the next. This phenomenon, known as biomagnification, seemed to affect larger birds more than smaller ones and not by simply killing them, but by altering how they metabolized calcium. Because they could not process calcium properly, these birds could not build shells strong enough to last through incubation. Thus, by the late 1960’s, populations of osprey, brown pelicans, and bald eagles were critically low and some species, such as the peregrine falcon, became extinct in certain regions. Fortunately, the devastating effects of DDT were recognized, and in 1972, this pesticide was banned for commercial use in the United States. However, in other parts of the world, DDT remained widely used. In 2001, 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. Ultimately signed by over 150 countries, the Convention limits the use of DDT to the prevention of malaria in select countries. The convention also places limitations on other long-lived, fat-soluble toxins named “ The Dirty Dozen ” such as dioxin, aldrin, chlordane, and PCBs. While these POPs are still used in many countries and therefore still pose a risk globally due to their ease of transport both through the air and in water, efforts are being made to eliminate them and their environmental threat. Pre-Lab Questions (Rewrite/Incorporate Questions in Your Answers in your NOTEBOOK!) 1. What is the difference between bioaccumulation and biomagnification? 2. What is DDT (dichloro-diphenyl-trichlorethane)? 3. Who identified the negative effects of DDT? What book did she write? 4. What effect did DDT have on larger birds? 5. Is DDT still used today? 6. What makes the Dirty Dozen “dirty”? (when you Google…it’s not fruits and vegetables)

Materials and Equipment: (per lab group) ● 100 M&Ms ● Paper Towel to lay M&Ms on ● 1 small plate labeled “OSPREY” ● 2 large cups: one labeled “EEL #1”, the other labeled “EEL #2” ● 5 medium cups labeled “MINNOW” Procedure 1. The pile of M&Ms represents the phytoplankton population in a lake. There are 100 M&Ms in the pile. Arrange your M&Ms in a 20 x 5 grid as seen below. Each box represents 1 phytoplankton. The printed “M” represents the amount of DDT (in ppm) the phytoplankton contaminated from pesticide runoff from a nearby agricultural area. Set up a similar grid in your Lab Notebook and mark the amount of toxin each phytoplankton has ingested. ● A clear, full “M” means that phytoplankton absorbed 1 ppm of DDT, so write a “ 1 ” in the corresponding box. ● If there is no “M”, then that phytoplankton did not ingest any DDT, so leave the corresponding box empty. ● If there is a partial “M”, then estimate how much of the “M” there is. For example, if there is only one hump of the “M”, then ~0.5 ppm of DDT absorbed by that phytoplankton, so fill the corresponding box with “ ½ ”. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2. Zooplankton in the lake (population size 20) each eat 5 phytoplankton. For simplicity’s sake, we will assume each zooplankton eats a column of phytoplankton. Record the amount of DDT each zooplankton has ingested. Zooplankton 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 3. Minnows (population size 5) in the lake each eat 4 zooplankton, ingesting energy and toxins stored in the zooplankton. Move the correct number of M&Ms from the zooplankton to Minnow cups. Set up a similar grid in your Lab Notebook and record the amount of DDT ingested by each minnow. Minnow 1 Minnow 2 Minnow 3 Minnow 4 Minnow 5 4. Two eels come across the minnow population. Eel #1 eats 2 minnows and Eel#2 eats 3 minnows. Move the correct number of M&Ms from the minnow cups into the eel cups. Set up a similar grid in your Lab Notebook and record the amount of DDT ingested by each eel. Eel 1 Eel 2 5. Finally, an osprey flies by and eats both eels. Move the correct number of M&M’s from the eel cups into the osprey plate. Calculate and then write the total amount of DDT ingested by the osprey onto the picture below. Osprey

4. Energy diagrams are typically drawn as pyramids or triangles (as done in Part E above). Why would it not be appropriate to draw energy diagrams as a rectangle showing the same amount of energy at each level? 5. Examine Data Trend: In an energy pyramid, there are more producers than consumers so the base of the food web is the largest and consists of producers. Compare your energy to the toxins pyramid. What do you notice? How might you explain this difference? Compare the amount of DDT found in the osprey with the amount of toxin found in one phytoplankton. BE SPECIFIC. Discuss numerical evidence. 6. Strategies to reduce the amount of pesticides used are referred to as a whole as Integrated Pest Management (IPM). Research and identify two IPM strategies that could be used to reduce or prevent insect pests instead of using DDT.