Chapter 15: Marine Ecosystems
Science under the 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 CO2 from fossil fuel use. This has the
potential 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 how Marc
Slattery and other scientists are monitoring ocean acidification:
http://www.youtube.com/watch?v=hZXoVpHnmbE.

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 CO2 is 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:
http://www.climatewatch.noaa.gov/video/2010/origin-impacts-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: http://www.epa.gov/bioiweb1/aquatic/marine.html.

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: http://www.epa.gov/bioiweb1/coral/index.html.
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 http://www.mpa.gov/aboutmpas/.

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
http://water.epa.gov/type/oceb/habitat/coral_index.cfm.
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 http://water.epa.gov/type/oceb/artificialreefs_index.cfm and
http://ngm.nationalgeographic.com/2011/02/artificial-reefs/harrigan-text