Chapter 15: Marine Ecosystems
Science underthe Sea: Aquanauts Explore an Ecosystem on the Brink
Story Abstract and Additional Information
This chapter examines the fact that marine ecosystems contain a huge diversity of life, though we know far less about ocean ecosystems than those on land. Many ocean ecosystems are suffering as a result of pollution, overfishing, misuse of the ecosystem’s resources, and global climate change. Of particular concern is the change in ocean chemistry caused by the release of CO2from fossil fuel use. This has thepotential to alter ocean ecosystems drastically, and some effects are already being seen. Choices we make today will influence the future of ocean ecosystems and the species that inhabit them.
Here are some of the key points in the story for this chapter:
Why is ocean acidification a problem?
- If present trends continue, by 2100 the ocean’s surface waters will be about 150% more acidic than they were in 1800. In 2003 scientists adopted the phrase “ocean acidification” to describe this coming catastrophe. One big concern is that as pH shifts, the availability of key nutrients like nitrogen and iron will change, plummeting in some areas, soaring in others, and threatening the stability of virtually all marine ecosystems. Watch this video to learn more about howMarc Slatteryand other scientists are monitoring ocean acidification:
- Acidification may already be affecting plankton. Overall, plankton biomass may have decreased as much as 40% in the twentieth century. Less plankton means that less CO2is taken in by the organisms, and more is left behind to further acidify the water or reenter the atmosphere. Watch this video from the National Oceanic and Atmospheric Administration (NOAA) to learn more about how increased CO2 in the atmosphere is contributing to ocean acidification:
What is the makeup of marine ecosystems?
- The world’s oceans are a wonderland of diversity. They cover about 70% of Earth’s surface and house a greater variety of flora and fauna than all land masses combined. Lots of ecosystems means lots of ecosystem services, including temperature moderation (ocean water absorbs a lot of heat and releases it slowly), nutrient cycling, and support for large populations of commercially valuable fish. Learn more from the Environmental Protection Agency (EPA) about marine ecosystems here:
- Coral reefs are especially valuable for their services: protection of coastal areas from storms, purification of the water (many reef occupants are filter feeders), provision of recreational opportunities, and support of important commercial fisheries. They even serve as a source of current and potential medicines, such as antibiotics and anticancer drugs. Learn more from the EPA about coral reefs:
How can we reduce threats to coral reefs and other ocean ecosystems?
- Scientists have been working to create marine protected areas (MPAs)—places where fishing and other human activities are restricted or completely prohibited. Evidence shows that in the right conditions, MPAs can significantly improve the marine ecosystems they encompass. Learn more about MPAs from the NOAA at
- Reducing beachfront development and ceasing the practice of coral reef harvesting for building materials keeps the areas intact and reduces exposure to land-based pollution. Nets dragged across the sea floor can destroy coral reefs and other seabed formations. Using other, safer methods in reef areas will protect the reef from these methods. Keeping populations viable by not overfishing improves an ocean community’s ability to withstand perturbations. Learn more from the EPA about efforts to protect coral reefs at
Additional information about other topics from this chapter:
Artificial Reefs
- Decommissioned military and commercial vessels are being converted into artificial reefs as part of fisheries resource conservation efforts. The EPA has prepared guidelines for cleaning up these vessels before they are turned into reefs. Learn more about the EPA guidelines and read about existing artificial reefs at and