Unit 3: Ocean Habitat and Community Ecology
Students will be able to identify the functional roles that organisms play in ocean ecosystems. How do human-induced changes in ocean conditions affect biodiversity, and thereby the health and resilience of a coral reef? Students explore and discuss the direct and indirect impacts that ocean acidification can have on species, food web dynamics, ecosystem function, and commercial resources. At the end of this unit the students should be able to articulate how changes in ocean chemistry can create negative outcomes for humans who depend on living ocean resources.
- Describe the ecological roles that organisms play within complex ecosystems.
- Give examples of how diversity links with ecosystem resilience in coral reefs.
- Examine how global climate change (i.e. increased ocean temperature and ocean acidification) jeopardizes the sustainability of coral reefs worldwide.
- Explain how changes in diversity and food web regime shifts affect people who depend on sustainable ocean resources.
This unit introduces students to the complex concepts involved in ecosystem diversity and function. They will discuss the challenges involved in scientific research to study the impact that global change has on biological communities, and they should be able to draw connections between global climate change and negative outcomes for coastal communities.
Context for Use
This unit can be used as a stand-alone unit or as part of the Ocean Sustainability Module. It can be used in an introductory marine or environmental science course. This unit is designed to be used in a classroom of 10–100 students over the course of one 50-minute class period. Work combines in-class activities and homework.
Description and Teaching Materials
Lecture (10 min)
Instructor starts with the first part of the Unit 3 lecture presentation (PowerPoint 4.8MB Oct26 16) (slides 1-8) that explains how corals are foundation species that create entire ecosystems, living space that functions as nursery and refuge for numerous fish and invertebrate species. These systems are the most species-rich habitats in the oceans, supporting ~25% of all marine species while taking up less than 1% of the ocean floor.
Notes on Lecture
Slide 1: Learning goals
Slides 2 through 7: The ecological roles (trophic roles) that members within a reef community play are introduced with emphasis on corals as foundation species. The importance of the relationship between corals and their endosymbiotic algae (zooxanthellae) is explained, and what happens when this relationship is disturbed (coral bleaching). The preferred living conditions for corals are discussed, which will allow students to look at changes in these conditions due to climate change in the second part of the lecture.
Examples are presented where changes in diversity affect reef community structure and adversely impact ecosystem function and resilience. A specific scenario will be described for ecosystem regime shifts due to "bottom-up" or resource-dependent change (i.e. nutrient pollution and algal overgrowth) and one scenario of regime shift due to "top-down" or predator-dependent factors (i.e. overfishing). Referring to the trophic pyramid diagram, these scenarios give an example of how students will be able to solve Activity 1.
Slide 8: Introduction of Activity 1 — talk through the provided (filled-in) example for guidance.
Activity 3.1 (10 min)
Students cooperate in small groups (~5 students) to fill in the worksheet for Activity 3.1. They are encouraged to use information provided during the first part of the lecture and the trophic pyramid diagram to complete the chart. They are asked to link specific organisms to their ecological roles (trophic modes) and trophic levels and predict the overall impact on reef resilience by choosing from the provided scenarios. By using their newly acquired knowledge and the lecture examples, they can decipher trophic connections to match potential impacts on reefs due to loss in functional diversity. - Activity 1_Handout (Acrobat (PDF) 34kB Oct22 16)
Notes on the activity: The instructor can adjust the number of blanks that students fill in for this activity, based on the existing knowledge of the students (editable version of Activity 1 spreadsheet (Excel 2007 (.xlsx) 14kB Oct26 16)). The current example does give some guidance for varying columns, but this can be adjusted as needed. The additional trophic pyramid diagram that depicts trophic levels on a coral reef with examples is a supporting tool for this activity.
Lecture continued (15 min)
The instructor continues the lecture (slides 9–12) to discuss the global status of reefs and how sustaining healthy marine ecosystems is a multi-dimensional challenge. It is discussed how predictions link future thermal stress to increasing coral bleaching, further jeopardizing coral reef survival. At this time, students are encouraged to consider why researching the impact of ocean temperature change together with ocean acidification on coral reef health is a formidable science challenge. Use the questions on slide 12 and gather students' thoughts on the topic in preparation for Activity 2 and the movie.
Activity 3.2 (15 min)
Provide the class with a printed question sheet for Activity 3.2: Activity 3.2 Handout (Acrobat (PDF) 111kB Oct28 16) / Activity 3.2 Handout (Microsoft Word 2007 (.docx) 21kB Nov6 16). Alert them to the fact that the answers will not be due as homework until next class but that they are strongly encouraged to take notes during the showing of the video clip "Sea Change: The Pacific's Perilous Turn" (~9 min). The video will have several examples of how ocean acidification affects ecosystems and adversely impacts single marine organisms, and subsequently changes diversity and food webs linked to humans who depend on sustainable ocean resources. Encourage class discussion after the video and give some pointers. Instead of providing students with the answers, encourage them to provide answers to each other. Emphasize that the video and associated article are available to them, and that they can stop or replay parts of the video to properly research answers for the homework. The students are provided with the word version for Activity 3.2, to familiarize themselves with the questions, take notes and fill in information. The students are asked to complete their homework and submit by next class.
Teaching Notes and Tips
For students not familiar with ecological terms such as ecosystem function, trophic levels, and food webs, more time should be spent explaining these terms in the first section of the PowerPoint and in context with Activity 1. Especially if the lesson is longer than 50 minutes, there will be more time to reiterate these basic terms. Alternatively, the time in a longer lesson can be used to finish Activity 2 in the classroom. However, the themes visited in that short documentary are rather complex and will be better assimilated if students are required to revisit the topics outside the classroom. The need for them to formulate and answer the homework questions will help with comprehension.
Activity 2 (which is completed as homework) could include an option for extra credit where the students are asked to research and provide an additional example for adverse impacts of ocean acidification on organisms and/or ecosystems not mentioned in class or in the documentary.
Lecture and Activity 1: Students have to identify the ecological roles (trophic roles) that organisms play within a reef community (Learning Goal 1) and have to link negative impacts on specific members (i.e. loss of functional diversity) to reef ecosystem function and resilience (Learning Goal 2).
Lecture and Activity 2: Students discuss predictions of how thermal stress and ocean acidification will jeopardize coral reef survival (Learning Goal 3) and use the provided news segment in Activity 2 to identify specific examples where commercially important species, and people who depend on them, are affected (Learning Goal 4).
- Activity 1 Key:
- Activity 2 Key:
References and Resources
- ScienceDaily — Various short articles on Coral Reef ecology
- The New York Times — Protecting Parrotfish on the Path to a Caribbean Reef Revival by Andrew C. Revkin
- EarthLabs Teaching Unit dedicated to corals
- NOAA Coral Reef watch — current data to identify bleaching hot spots
- PBS short — Coral Reefs Die as Ocean Temperatures Rise, Water Acidifies
- National Geographic Video — Caribbean Coral Reefs
- BBC —Where you can find Coral Beginnings, Limestone Structure, Feeding and Competition, and Mass Spawning on Great Barrier Reef
- California Academy of Sciences — Demystifying ocean acidification and biodiversity impacts