294 CHAPTER 11 The Ocean and Fisheries
pollute the adjacent water and also causes a net loss of wild
fish because many of the fishes farmed are carnivorous.- Marine pollution is generated by many human activities,
including the release of trash and contaminants through
commercial shipping, ocean dumping of sludge and industrial
wastes, and discarding of plastics that are potentially harmful to
marine organisms. Marine environments are also deteriorated
by coastal development and the extraction of offshore minerals. - The ocean conveyor belt moves cold, salty, deep-sea water
from higher to lower latitudes, affecting regional and possibly
global climate. Global climate change associated with human
activities may alter the link between the ocean conveyor belt
and global climate.
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Addressing Ocean Problems 291- International initiatives aimed at protecting the global
ocean include the U.N. Convention on the Law of the Sea
(UNCLOS), a “constitution for the ocean” that protects ocean
resources, and the U.N. Fish Stocks Agreement, the first
international treaty to regulate marine fishing. In the United
States, marine fisheries are regulated by the Magnuson-
Stevens Fishery Conservation and Management Act. - Long-term goals for halting and reversing destruction of the
ocean focus on adopting an ecosystem-based approach to
management of ocean environments. Consolidating ocean
programs, funding research on marine ecosystems, and
enhancing ocean education to instill in citizens a stewardship
ethic could improve U.S. ocean policy. - The ocean and the atmosphere are strongly linked. The
El Niño–Southern Oscillation (ENSO) event, which is
responsible for much of Earth’s interannual climate variability,
is a periodic, large-scale warming of surface waters of the
tropical eastern Pacific Ocean that temporarily alters both
ocean and atmospheric circulation patterns. A La Niña event
occurs when surface water in the eastern Pacific Ocean
becomes unusually cool. Its effects on weather patterns are
less predictable than an ENSO event’s effects.
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Major Ocean Life Zones 278- The vast ocean is subdivided into major life zones. The
biologically productive intertidal zone is the area of shoreline
between low and high tides. The benthic environment is the
ocean floor, which extends from the intertidal zone to the
deep-ocean trenches. Most of the benthic environment consists
of sediments where many animals burrow. Shallow benthic
habitats include sea grass beds, kelp forests, and coral reefs.
The pelagic environment is divided into two provinces. The
neritic province is the part of the pelagic environment from
the shore to where the water reaches a depth of 200 m (650 ft).
Organisms that live in the neritic province are all floaters or
swimmers. The oceanic province, “the deep sea,” is the part of
the pelagic environment where the water depth is greater than
200 m. The oceanic province is the largest marine environment,
comprising about 75 percent of the ocean’s water.
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Human Impacts on the Ocean 284- The most serious problem for marine fisheries is the
overharvesting of many species to the point that their
numbers are severely depleted. Fishermen usually
concentrate on a few fish species with high commercial
value. In doing so, they also catch bycatch: fishes, marine
mammals, sea turtles, seabirds, and other animals caught
unintentionally in a commercial fishing catch and then
discarded. Aquaculture is the growing of aquatic organisms
(fishes, shellfish, and seaweeds) for human consumption.
Aquaculture is common in developing nations with abundant
cheap labor, and it is limited by the size of the space
dedicated to cultivation. Aquaculture produces wastes that
Key Terms
aquaculture 287
benthic environment 278
bycatch 286
El Niño–Southern Oscillation
(ENSO) 276
gyres 274intertidal zone 278
neritic province 281
oceanic province 283After Halperin, B.S., et al.
“A global map of human
impact on marine ecosystems.”
Science, Vol. 319, No. 5865,
pp. 948–952 (February 15, 2008).
Mapping Human Impacts.