After seven years of teaching middle school

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1 Disrupted food webs: Exploring the relationship between overfishing and dead zones in the Chesapeake Bay by Yael Wyner After seven years of teaching middle school environmental science, I am frustrated with food webs. Why do they seem so easy, even though disruptions of healthy food webs have, time and time again, lead to unforeseen complex environmental disasters? After spending many hours contemplating this question, I came across a wonderful video on the unforeseen and misunderstood consequences of overfishing in the Chesapeake Bay. This activity is an effort to adapt the groundbreaking article from Science on which the video is based for use in my classroom (Jackson et al. 2001). In the activity, students analyze historic and present-day food webs and graph historic and present-day Chesapeake Bay data to learn how food web complexity is easily overlooked, and why that complexity is important for healthy ecosystems. Finally, students use seafood cards to learn how their seafood choices can affect the world s oceans. I used these lessons in my seventhgrade environmental science classes in a New York City public school for gifted learners. These lessons are appropriate for a wide range of learners, although more time may need to be allotted, particularly when students are completing the graphing activity. After completing the activity, students will be able to understand that food webs describe the feeding relationships in an ecosystem, food webs are made up of many FIGURE 1 whales birds predatory invertebrates OYSTERS microbes different food chains, ecosystem stability is dependent on all ecosystem components, including the balance between primary consumers (filter feeders) and decomposers, excess nutrients lead to eutrophication and dead zones, filter feeders limit excess nutrients in estuary ecosystems, overfishing destabilizes ocean ecosystems, making them vulnerable to eutrophication, shifting baselines are a reason that society fails to Chesapeake Bay before fishing Historic grazing fish sharks seals alligators predatory fish zooplankton phytoplankton/algae jelly fish sea floor plants sea turtles manatees worms/ amphipods seagrass detritus (rotting material, i.e. high nutrient levels) 78 SCIENCE SCOPE

2 notice the decline of many ocean ecosystems, ecosystem decline occurs slowly over time, causing us to mistakenly view severely degraded and poorly functioning ecosystems as normal and relatively healthy, and graphs are important tools for comparing and seeing patterns in data. Part 1 Introduction to the problem: Why are there dead zones in the Chesapeake Bay? (20 minutes) As formative assessment, you can test students on food webs or on eutrophication. To engage students, I use a short slide show (the slide show is available online at I begin with a map of the Chesapeake Bay and close-up images of the rivers from six states and the District of Columbia that feed into the bay. I tell students that the bay is the largest estuary in the United States and that no other American estuary has a higher yield of fish and seafood (including blue crab, oysters, clams, and striped bass). I then ask students to raise their hands if they or their parents eat seafood. I tell students that the seafood they eat may even come from the bay. In this way, I hope to make the lesson relevant to my students who do not live near the bay. Next, I use photos of algal blooms and dead fish to introduce the problem of pollution, eutrophication, and dead zones in the bay. Photos of nutrients and suspended sediment entering the bay from places like farms (fertilizer and manure runoff) and cities (sewage) are used to discuss the factors leading to high nutrient levels in the bay. Particular language and concepts that I include in the discussion of eutrophication are the relationship between detritus (rotting material) and microbes (the microscopic organisms that eat the detritus), because these terms will appear when students analyze their food webs. The slide show contains a step-by-step process of how dead zones are made and uses the photos to illustrate the process. This section was review for my students, so I asked them Activity Worksheet 1: Questions about the Chesapeake Bay food web before large-scale fishing (to be distributed with Figure 1; answers in italics; blank worksheets available at 1. Which organisms are abundant in this ecosystem? Whales, sharks, seals, alligators, birds, predatory fish, sea turtles, grazing fish, predatory invertebrates, zooplankton, manatees, oysters, seafloor plants, sea grass. 2. Which organisms are rare in this ecosystem? Phytoplankton/algae, jellyfish, worms/amphipods, microbes (detritus). 3. List the producers and consumers in this ecosystem. Producers: phytoplankton/algae, seafloor plants, sea grass. Consumers: whales, sharks, seals, alligators, birds, predatory fish, sea turtles, grazing fish, predatory invertebrates, zooplankton, sea cows, jellyfish, zooplankton, oysters, worms/amphipods (also decomposers). 4. Find and write out a six-step or greater food chain. Phytoplankton/algae oyster predatory invertebrates predatory fish seal shark whale or others. Notice the length of the food chain. Land food chains are not this long. 5. What do the microbes eat? Are they producers, consumers, or decomposers? Microbes eat the detritus and are therefore decomposers. 6. If whales and turtles become rare in this ecosystem, what would you expect to happen to the number of jellyfish? The jellyfish population should go up because nothing else eats them. 7. If whales, sharks, seals, and alligators were removed from the ecosystem, what would you expect to happen to the numbers of predatory fish? Their populations should go up because nothing else, except birds, eats them. 8. If the oyster population was reduced, what would you expect to happen to the quantity of microbes, phytoplankton/algae, and detritus? The microbes should increase because nothing else eats them. The phytoplankton/algae should also increase, but not as much because zooplankton eat them. If the phytoplankton/algae increase, then the detritus should increase because when the phytoplankton/ algae die, they become detritus. 9. Predict how the present-day food web will look different than the historic food web. Manatees and alligators will be missing. M a r c h

3 to recall what they knew about algal blooms and eutrophication. Students summarized their knowledge as 9 list of steps: 1. Sewage runoff and fertilizers contribute excess nutrients into the water, leading to an explosion of algae (algal blooms). The availability of nitrogen is no longer a limiting factor. 2. Like all living things, algae die and become detritus that is decomposed by microbes. 3. The population of microbes explodes because of the large amounts of detritus available to eat. 4. Like us, microbes use oxygen to make energy. The large amounts of microbes use up the oxygen in the water. 5. The water now has low dissolved oxygen, killing fish and other organisms that need the oxygen to live. 6. This is now a dead zone. FIGURE 2 whales birds predatory invertebrates oysters microbes After the discussion of the causes of dead zones, the class summarizes what appears to be obvious: The excess nutrients that people are contributing to the bay are causing the dead zone problem in the bay. However, in an effort to learn more about the dead zone problem, I tell students that we will analyze the feeding relationships of all organisms that make up the bay ecosystem. But, in order to understand the feeding relationships among organisms in today s Chesapeake Bay ecosystem, we need to know what organisms lived there in the past. We will begin by investigating what the Chesapeake Bay ecosystem looked like 300 years ago, before the arrival of European settlers and large-scale fishing. Part 2 The Chesapeake Bay before European settlers and large-scale fishing (Figure 1 and Activity Worksheet 1, minutes) Chesapeake Bay with fishing Today sharks grazing fish people predatory fish zooplankton phytoplankton/ algae detritus (rotting material, i.e. high nutrient levels) seals JELLYFISH sea floor plants alligators sea turtles I hand each group of two students a food web of the Chesapeake Bay before large-scale fishing and a worksheet (Figure 1 and Activity Worksheet 1). Students use the worksheet to analyze the food web. Before students begin analysis, we review the important terms in the food web and the food web key. This step is very important, because some of the language in the food web is difficult to understand without discussion, and because the first food web is very full of information. (This complexity is one of the points of the exercise. The food web before fishing is very hard to read because it is so complex. The food web with fishing is easy to read by comparison because most of the complexity has been removed!) The worksheet prepares students to compare this historic food web of the Chesapeake Bay (Figure 1) to the food web of the present-day Chesapeake Bay ecosystem that they will receive next (Figure 2). Students use the historic food web to determine abundant and rare species in the ecosystem and to predict the consequences of removing certain species from the ecosystem. Students also practice important basic skills such as determining producers, consumers, and decomposers in an ecosystem and separating out small food chains from the larger food web. By contextualizing these terms into a dynamic and changing food web, students begin to learn why these ecological terms are important for scientific understanding. x manatees x worms/ amphipods seagrass 80 SCIENCE SCOPE

4 Activity Worksheet 2: Questions for Chesapeake Bay food web with large-scale fishing (answers in italics; to be distributed with Figure 2) 11. Which organisms are abundant? People, birds, jellyfish, worms/amphipods, phytoplankton/algae, microbes, and detritus (though not an organism). 12. Which organisms are rare or extinct? Whales, sharks, seals, alligators, predatory fish, sea turtles, grazing fish, predatory invertebrates, zooplankton, sea cows, oysters, seafloor plants, and sea grass. 13. Redraw the food web including only the abundant species. What do you notice? The only part of the food web that can successfully be redrawn is the relationship among the detritus, microbes, algae, and worms/amphipods the very low trophic levels. Higher trophic levels are not included. The complexity of the ecosystem has been lost. Also, people have been added to the ecosystem and jellyfish that were once rare are now abundant. 14. How is this food web similar to different from the food web unaffected by people? Similar: Many of the same organisms are still there, they are just much diminished. Birds are common in both food webs. Different: Some organisms are now locally extinct, such as alligators and manatees. Many common organisms are now rare, such as whales, sharks, seals, predatory fish, sea turtles, grazing fish, predatory invertebrates, zooplankton, sea cows, oysters, seafloor plants, and sea grass. Jellyfish are now abundant. People have been added to the ecosystem. 15. Why do you think jellyfish are now abundant? There are few sea turtles or whales to eat them. 6. Why are there fewer predatory fish if there are fewer whales, sharks, seals, and alligators? People are fishing them. 17. From what you know about the relationship between high levels of nutrients and algae growth, why have the phytoplankton (floating plants or algae) increased? The algae are no longer limited in growth by the levels of nutrients in the water. They have nutrients and sunlight. They can now grow quickly. 18. What happened to the seafloor plants? If fewer organisms are eating them, shouldn t their numbers have increased? Why are they rare now? Hint: Like all plants, what do the seafloor plants need to grow? What does nutrient run-off cause to grow that would limit the resource that seafloor plants need to grow? Explain. Thick layers of floating algae block the sunlight from reaching the seafloor plants that grow down below. Without sunlight, the seafloor plants cannot grow. 19. How does this food web connect to the problem of high nutrient levels in the water? Hint: Oysters filter the nutrients, microbes, and phytoplankton from the water. Use the food web to explain what happened to their numbers and why. Oysters filter the water, cleaning it of microbes, algae, and excess nutrients. People have harvested the oysters, taking away the bay s natural cleaner. Without the cleaner, the bay has become very dirty. 10. Based on your answer to question 9, make a hypothesis for how harvesting of oysters affects nutrient pollution. Hypothesis: If people overharvested the oysters, then nutrient pollution would increase or people overharvested the oysters, leading to an increase of nutrient levels in the bay. 11. What type of data would you need to collect in order to test your hypothesis? Hint: You would need to compare historic and present-day data on two elements of the ocean. What are those elements? We would need to have historic and present-day data on the number of oysters and the nutrient levels in the bay. When a group completes its worksheet and I have checked over their answers using the answer sheet (Activity Worksheet 1), I hand the group a new worksheet and a diagram of today s Chesapeake Bay food web with large-scale fishing (Figure 2 and Activity Worksheet 2). I check student work to see if students can make food chains, understand which species are rare and abundant, and understand how the species interact with one another. It is not necessary to have a full-class discussion after this worksheet, as students work at different rates, which allows me to have personal give-and-take with each student group. Part 3 The Chesapeake Bay today with large-scale fishing (Figure 2 and Activity Worksheet 2, minutes) This activity follows the same format as the previous food web and worksheet. Working in the same groups of two, students use the new worksheet to analyze the food web of today s Chesapeake Bay with large-scale M a r c h

5 fishing (Figure 2 and Activity Worksheet 2). This food web is much less complex (and easier to read) than the food web that students previously analyzed. Some species are missing, including alligators and manatees, and others are now rare (e.g., whales, sharks, seals, predatory fish, grazing fish, predatory invertebrates, oysters, seafloor plants, sea grass, and sea turtles). Many feeding relationships that were once strong are now weak. Students are asked to think about why the food web is so different and how the changed food web might impact ecosystem health. The worksheet reviews many important issues, such as asking students why jellyfish are abundant, if historically they were rare, and why predatory fish are rare, even though their shark, seal, and whale predators are now rare. The worksheet then addresses the problem of pollution in the bay. Students are asked to use what they know about eutrophication to explain why the algae are now abundant in the bay. As a side note, students are also asked how the abundance of algae that float might affect the abundance of plants that grow below them (e.g., seafloor plants and sea grass). These questions begin to explain the state of the bay today. Nutrients added to the bay feed the growth of algae. The abundance of algae floating on the surface block the sunlight from reaching seafloor plants, causing many of them to die. Finally, students are asked to connect the high levels of nutrients, algae, and microbes to the loss of the oyster filters in the bay. Students develop a hypothesis about how the loss of oyster filters might contribute to the high nutrient levels in the bay. (If people overfished the oysters, then nutrient pollution would increase.) If students have difficulty making this hypothesis, I walk them through the historic food web. I ask them how oysters get their food (filtering the nutrients) and what would happen to the level of nutrients if the oysters stopped filtering (it would go up). Once students make the prediction that without oysters filtering the water, nutrient levels would go up, I point out that they have made their hypothesis. Students then determine the type of data they would need to analyze to test their hypothesis. Again, I use the food webs to help students who have difficulty with this task. I ask students to tell me why the two food webs appear to be so different and why that might help us in testing the hypothesis (comparing preharvesting and present-day food webs can tell us what is different today). This statement leads to an understanding that students need to analyze historic and present-day oyster and nutrient levels to test their hypothesis. After students make this determination, I give them the data on current and historic levels of oysters and nutrients in the bay (Activity Worksheet 3). I tell students that this page contains data on past oyster-harvesting levels and past pollution levels in the bay. I ask them to think about why there are no data on oyster catches before 130 years ago (people were not yet harvesting the oysters). Also, we discuss the two different scales for the oyster and pollution data. The pollution data are on a scale of 1 (no pollution) to 8 (very polluted). Part 4 Graphing analysis of historic and present-day nutrient pollution levels in the bay in comparison to historic and present-day numbers of oysters in the bay: Testing the hypothesis that oysters reduce nutrient pollution in the bay (Activity Worksheet 3, minutes). Students graph the oyster and nutrient levels and use the worksheet to analyze their results (Worksheet 3). If needed, it is also possible to prepare graphs with axes already labeled. Once all students have the data table and worksheet (Activity Worksheet 3), we have a whole-class discussion reviewing the data, relating it back to the hypothesis, and discussing the listed points below. We determine as a class how to set up the graphs and discuss any points that might confuse students. I find this approach to be an effective strategy, because it gives students who are moving more quickly time to think about their plotting strategies and allows students who may find this activity more difficult to have an opportunity to discuss the graphing issues with the class. 1. The graphs have two y-axes with different scales. a. An axis for oyster catch with numbers going into the hundreds of thousands of metric tons. b. An axis for nutrient level with the highest number being 8 (as measured by the ratio of floating algae to seafloor algae found today and historically). (Greater nutrient levels in the water lead to more floating algae and less seafloor algae because the Sun is blocked by the floating algae.) 2. The x-axis includes data from hundreds of years ago up through present day. The interesting data points do not begin until 300 years ago, and then only really get detailed in the past 150 years. Students often distort the scale of the x-axis in order to fit all of their 82 SCIENCE SCOPE

6 Activity Worksheet 3: Oyster catch versus nutrient levels in the Chesapeake Bay Testing the hypothesis that oysters reduce nutrient pollution in the bay (answers in italics and background note to teachers in bold). Plot and connect your data points on one graph 1. Oyster catch in relation to years before present 2. Nutrient levels in relation to years before present Helpful hints for graphing 1. Years before present should go on the x-axis. a. To have enough room, use the long side of the graph paper for this axis. b. Begin your graph at 300 years before present to have enough room on your x-axis for all of your data points. c. Make sure that your increments are consistent even though you do not have all the data points to plot. 2. You will need two y-axes, with different scales for oyster catch (high of 600,000) and nutrient level (high of 8). 3. Use a pencil to plot so that you can erase any mistakes. 4. Your graph plan should be approved by me before you begin graphing. Questions 1. What is the independent variable? Time. 2. What are the dependent variables? Oyster catch and nutrient levels. 3. Why do you think nutrient pollution in the bay began to increase about 250 years ago? Hint: It has to do with the arrival of European settlers. European settlers began to clear land for farming of crops and cattle, leading to greater nutrient input into the bay. 4. Nutrient levels hold steady for almost 200 years at 3 and then suddenly increase 60 years ago to 8. Use your graph to determine what happened to the oyster catch at the same time (60 years ago). Oyster catch also drastically declined. 5. How might the decline of oysters lead to the sudden increase in nutrient levels in the bay 60 years ago? Use what you know about the role of oysters in the Bay food web to answer this question. Oysters were keeping the nutrient levels relatively stable in the bay by filtering the nutrients, sewage, animal waste, and fertilizer that was running into the bay. Once the oysters were removed from the bay 60 years ago, there were no more oysters to clean the nutrient overload from the bay, causing the nutrient level to drastically rise in the bay. (It is thought that oysters used to filter the entire water column of the bay every three days. Now it is thought that the water column is only filtered twice a year.) 6. How does this graph contribute to scientific understanding of the role of oysters in controlling nutrient Years before present Oyster catch in metric tons Nutrient level measured as planktonic/benthic diatom ratio* 1000 No data No data No data No data No data No data , , , , , , , , , ~0 8 0 ~0 8 * This is a ratio between a type of floating algae and a type of sea-floor algae. The ratio has been shown to be a good indicator of pollution levels. Cores of the ocean floor can be collected to measure historical planktonic/benthic diatom (algae) ratios. levels? Analysis of the data show that pollution levels dramatically increase at the same time that oysters are removed from the bay. The data provide evidence that loss of oysters and their role as filter feeders in the bay has contributed to the high pollution levels in the bay. (It is also possible to infer from the graph that high pollution levels led to the decline in oysters. Nutrient input did not suddenly increase 60 years ago, but harvesting pressure remained strong.) 7. Why are so few oysters being caught today compared to 100 years ago? There are not enough oysters in the bay to make oyster harvesting worthwhile. (Paradoxically, the pollution in the bay has made the bay hospitable to an oyster parasite that infects and kills the American oyster, making reintroduction of the oyster difficult.) 8. How would you propose to solve the nutrient problem and also help the oyster industry? Add oysters to the bay in order to clean the water. If native oysters cannot withstand the pollution, introduce a nonnative oyster that can withstand it (which can potentially have devastating, unforeseen consequences to the health and complexity of the bay ecosystem). M a r c h

7 Activity Worksheet 4 Summary (answers in italics) 1. How have humans affected the Chesapeake Bay food web? People have overharvested most of the species in the Chesapeake bay, including whales, sharks, seals, alligators, sea turtles, predatory fish, grazing fish, predatory invertebrates, and oysters. Algal blooms caused by pollution and the lack of oysters in the bay have led to the decline of ocean-floor plants like sea grass and an overgrowth of bacteria. Jellyfish that were once rare are now common. Manatees and alligators are no longer even present in the ecosystem. 2. Explain the role that oysters play in keeping the nutrient levels of the bay low. Oysters filter the nutrients in the bay. This filtering prevents an overgrowth of algae (algal blooms); an overgrowth of algae leads to the formation of dead zones. 3. Use your food webs and data from Part 3 to list at least five consequences of the altered food web of the Chesapeake Bay. lots of nutrient pollution algal blooms, dead zones, cloudy water lots of jellyfish lots of worms/amphipods no manatees no alligators very few sea turtles, etc. 4. How can understanding historic ecosystem food webs help us understand today s ecosystems? The only way to truly understand the health of today s ecosystems is to be able to compare them to what they looked like in the past. It is only possible to understand how ecosystems have changed if we know what the ecosystems looked like originally. The role of oysters in keeping the Chesapeake Bay clean was overlooked because people just assumed that the Chesapeake bay ecosystem always contained the same composition of organisms and that the only aspect of the bay that had changed was the additional nutrients added to the bay by people. Only after accounting for the previous complexity of the Chesapeake bay ecosystem is it possible to understand that the organisms living in the bay also played a role in keeping the bay clean and unpolluted. data points. I suggest that they use the long part of the page for their x-axis in order to keep a proper scale and be able to easily plot all of their data points. I also ask them to begin their graph 300 years before present day, rather than on the earlier dates. Students must receive approval of their graphing strategies before proceeding with the graphing. I check to see if students have their axes properly labeled, increments properly spaced, and graph properly titled. If these elements are missing, incomplete, or inaccurate. I ask students to show me how to correct the inaccuracy, i.e., if the increments are incorrect, I point it out and ask students why those increments might not be effective. When these tasks are complete, students complete a summary worksheet of the activity (Activity Worksheet 4). Part 5 Summary worksheet of the activity (Activity Worksheet 4, 20 minutes) This part of the activity asks students to summarize what they learned from analyzing historic and present-day food Webs and data on historic and present-day oyster-catch and nutrient levels. I give students a short time to think about the questions and then we discuss them as a class. Students summarize how fishing has changed the Chesapeake Bay ecosystem. They cite the decline of most major ecosystem organisms, including the localized extinction of manatees and alligators. Students also recognize that, although most species are fewer in number than they were before fishing, they are still present today, which gives us an opportunity to rehabilitate the ecosystem. Students are asked to summarize the role of declining oysters in the bay s dead zones. Without oysters cleaning the water of excess nutrients (fertilizer, manure, and sewage), the bay is overrun with nutrients, leading to algal blooms and dead zones. In a discussion with my students about their summaries, students are surprised to learn that oysters used to filter the bay in three days; now, with oyster harvesting, the bay is filtered once every six months. The final question on the summary worksheet asks students about the importance of analyzing historic data and the role of historic baselines. I use the discussion of historic baselines to lead into the videos about the Chesapeake Bay. 84 SCIENCE SCOPE

8 Part 6 Watching media about the Chesapeake Bay and distribution of seafood cards (40 minutes with discussion) Once the summaries are complete and we have discussed them, we watch two videos, Rediagnosing the Oceans and Jellyfish and Bacteria. Both videos are available for free download from lines.org/videos. The first video, Rediagnosing the Oceans (11 minutes), uses the example that students just investigated, oyster harvesting in the Chesapeake Bay, to explain why understanding historic baselines is important for understanding ocean ecosystems. (Note: This video has incredible pictures of mountains of oysters harvested from the bay, which students might not see if you do not point them out.) The video then introduces three other scientifically supported examples from other American ocean ecosystems to emphasize the importance of historic baselines. After watching this video, we discuss other shifting baselines, such as climate (today versus 30 years ago), increased life expectancy (today versus 100 years ago), or even what is considered a normal level of cell phone texting (adults versus childrens viewpoints). The next video, Jellyfish and Bacteria (less than 1 minute), is a humorous animation of ocean ecosystems that are overrun by jellyfish and bacteria. The video is set to the tune of Ebony and Ivory. The first verse is Jellyfish and bacteria that s what you get when the ocean is inferior. Side by side from the Black Sea to the Chesapeake Baaaaybeee. This video is a fun opportunity for students to sing along and get excited about what they learned. I watched this video multiple times with my students because they thought it was funny and because they wanted to get the sing-along part right. Finally, we discussed seafood cards, a color-coded, wallet-sized list of healthy and overfished seafood species (green for healthy, red for overfished) to let students know that there is something positive that they can do to help the oceans. (The cards are available from the Blue Ocean Institute, We go over the list to discuss the best and worst seafood choices for our dinner plates. An ironic note is that oysters are considered a very good seafood choice today because they are not wild caught (farm raised) and filter the water while they grow. (Not all farm-raised seafood is a good choice; farm-raised salmon and shrimp are major sources of pollution and habitat destruction.) Conclusion My students were excited about this real-world example that connected to their everyday seafood choices. In fact, many students went home and insisted to their parents that they should only buy green seafood choices. I was also satisfied with this activity because students were finally able to use what they learned about ocean ecosystems and apply it to a diagram of a local terrestrial ecosystem. When I showed my students a food web of a historic northeast forest/pond ecosystem and asked them how people disrupt it, they were able to apply knowledge that they had learned earlier in the year. Students reasons as to why food webs are being disrupted were as follows: Wolves have been removed, wolves had prevented the deer from eating all of the young trees. Invasive species have been introduced, such as gypsy moths and Asian longhorned beetles, thereby harming the trees. Trees have been cut down, leading to erosion and nutrient runoff into the pond and causing algal blooms. Answers such as these indicate that students have a better understanding of how we impact food webs and why they are important for a healthy, functioning natural world. Acknowledgments Thanks to Janice Koch, Steve Gano, and Rob DeSalle for helping to articulate the ecology disrupted approach. Thanks also to Sarah Fogelmann for providing valuable feedback after teaching these units in her class. Reference Jackson, J.B.C., M.X. Kirby, W.H. Berger, K.A. Bjorndal, L.W. Botsford, B.J. Bourque, R.H. Bradbury, R. Cooke, J. Erlandson, J.A. Estes, T.P. Hughes, S. Kidwell, C.B. Lange, H.S. Lenihan, J.M. Pandolfi, C.H. Peterson, R.S. Steneck, M.J. Tegner, and R.R. Warner Historical overfishing and the recent collapse of coastal ecosystems. Science 293 (5530): Yael Wyner (ywyner@ccny.cuny.edu) is an assistant professor in the Department of Secondary Education at the City College of New York in New York, New York. M a r c h