Download This Full Lesson: Marine Ecosystems
Lesson Description: Students will gain a better understanding of the intricacies within the Gulf of Maine marine ecosystem after completing this lesson. A classic example of how small changes can affect an entire ecosystem is the sea urchin-kelp story in Maine. Following the collapse of the cod fishery in Maine, green sea urchin populations exploded. The ecosystem became an urchin-dominated system. In the 1980s, fishermen discovered the high value of harvesting sea urchins and the aggressive overharvesting of the green sea urchin resulted in massive declines along the coast. Because urchins are grazers (they eat kelp and other macroalgae), the decline of the urchin population resulted in a shift towards a kelp forest ecosystem. Most fishermen today report seeing a lot of kelp and few urchins. The relatively new kelp forest system is the perfect environment for American lobster and crabs, both of which are natural predators of urchins. This is an example of a tipping point in an ecosystem, shifting from an urchin-dominated system to a dense kelp forest system.
What can we learn from this story? Does it make sense to manage individual species or an ecosystem as a whole? There is a new movement to shift from single species management to Marine Ecosystem-Based Management (EBM). According to the Scientific Consensus Statement on Marine Ecosystem-Based Management, “EBM is an integrated approach to management that considers the entire ecosystem, including humans. The goal of EBM is to maintain an ecosystem in a healthy, productive and resilient condition so that it can provide the services humans want and need. EBM differs from current approaches that usually focus on a single species, sector, activity or concern; it considers the cumulative impacts of different sectors”. In New England there is work being done to transition to this management framework. It will take a lot of effort and it is expensive to implement but once it is established, EBM has the potential to greatly benefit all who rely on a healthy ocean for their livelihoods.
There are two parts to this lesson. The first half of the lesson is devoted to the urchin-kelp story. Teachers can use the resources below to introduce this topic and help students understand the lessons learned from this story. The second half of the lesson is a hands-on activity from NOAA that will allow students to model a marine food web and a potential ecosystem collapse. Students will write an explanation of what they think might happen if a small change were to occur in the marine ecosystem in their backyards.
Essential Questions:
- Since the ocean is so large, why do small changes make a difference?
- How do humans interact with the marine ecosystem?
- What is ecosystem-based management?
Learning Objectives:
Students will
- explain recent changes in the Gulf of Maine (GoM) ecosystem with regard to ground fish, sea urchins and kelp.
- describe the human factor in the changing GoM ecosystem and the role that EBM could have on the GoM ecosystem.
| NGSS: |
MS-LS2-4; HS-LS2-6; HS-LS4-5 |