Page 451 - Environment: The Science Behind the Stories

Nutrient pollution in coastal waters also promotes the at the surface of the open ocean, returning periodically to nest-
growth of algae, which are smothering reefs in the Florida ing sites on islands and coastlines.
Keys and in many other regions. Moreover, coral reefs sustain In the little-known deep-water ecosystems, animals have
damage when divers stun fish with cyanide to capture them for adapted to tolerate extreme water pressures and to live in
food or for the pet trade, a common practice in waters of Indo- the dark without food from autotrophs. Many of these often
nesia and the Philippines. Finally, as global climate change bizarre-looking creatures scavenge carcasses or organic detri-
proceeds, the oceans are becoming more acidic as excess car- tus that fall from above. Others are predators, and still others
bon dioxide from the atmosphere reacts with seawater to form attain food from symbiotic mutualistic (p. 98) bacteria.
carbonic acid. Acidification threatens to deprive corals of the Ecosystems form around hydrothermal vents (p. 51) in
carbonate ions they need to produce their structural parts (see the ocean, where heated water spurts from the seafloor, car-
The Science behind the Story, pp. 446–447). rying minerals that precipitate to form rocky structures.
A few coral species thrive in waters outside the tropics Tubeworms, shrimp, and other creatures in these systems use
and build reefs on the ocean floor at depths of 200–500 m symbiotic bacteria to derive their energy from chemicals in
(650–1650 ft). These little-known reefs, which occur in cold- the heated water rather than from sunlight, a process called
water areas off the coasts of Norway, Spain, the British Isles, chemosynthesis. They manage to thrive within amazingly nar-
and elsewhere, are only now beginning to be studied by sci- row zones between scalding-hot and icy cold water.
entists. Already, however, many have been badly damaged by
bottom-trawling (p. 457)—the same practice that has drasti-
cally degraded the benthic habitats of groundfish such as the Marine Pollution
Atlantic cod. Norway and other countries are now beginning
to protect some of these deep-water reefs.
People have long made the oceans a sink for waste and pol-
lutants. Even into the mid-20th century, it was common for
Open-ocean ecosystems vary coastal U.S. cities to dump trash and untreated sewage along
in their biodiversity their shores. The Clean Water Act (p. 194) reduced the dis-
charge of point-source pollution (p. 426) into the oceans. But
Biological diversity in pelagic regions of the open ocean is a great deal of pollution is non-point-source pollution that
highly variable in its distribution. Primary production (p. 129) comes from countless small things we all do and from items
and animal life near the surface are concentrated in regions of we throw away far inland. For the oceans are downstream
nutrient-rich upwelling. Microscopic phytoplankton constitute from everywhere: As long as rivers flow to the sea, much of
the base of the marine food chain in the pelagic zone. These pho- our pollution on land sooner or later ends up in the oceans.
tosynthetic algae, protists, and cyanobacteria feed zooplankton Oil, plastic, toxic chemicals, and excess nutrients all even-
(p. 93), which in turn become food for fish, jellyfish, whales, tually make their way into the oceans. Sewage and trash from
and other free-swimming animals (Figure 16.15). Predators at cruise ships and abandoned fishing gear from fishing boats add
higher trophic levels include larger fish, sea turtles, and sharks. to the input. The scope of trash in the sea can be gauged by the
Fish-eating birds such as puffins, petrels, and shearwaters feed amount picked up by volunteers who trek beaches in the Ocean
Conservancy’s annual International Coastal Cleanup. Over 25
years, more than 65 million kg (144 million lb) of waste have
Figure 16.15 The uppermost reaches of ocean water con- been collected from the world’s beaches as part of this program.
tain billions upon billions of phytoplankton––tiny photosyn-
thetic algae, protists, and bacteria that form the base of Plastic debris endangers marine life
the marine food chain. This part of the ocean is also home to
zooplankton, small animals and protists that dine on phytoplank- Plastic bags and bottles, fishing nets and line, and small
ton and comprise the next trophic level. particles of plastic and other trash can harm marine creatures.
Organisms can become entangled in such debris and drown,
or they may die as a result of ingesting material they cannot
digest or expel (Figure 16.16a). Floating plastic and debris con-
centrates in gyres, areas of the ocean where currents converge
(see The Science behind The STory, pp. 452–453). The North
Pacific Gyre contains the Great pacific Garbage patch, an area
larger than Texas, in which tiny pieces of floating plastic out-
number organisms by a 6 to 1 margin.
Because plastic is designed not to break down, it can
drift for decades before washing up on beaches. Plastic does
degrade slowly in seawater and sunlight, but in doing so, breaks
down into smaller and smaller bits that become more and more
numerous. This can actually make things worse: The oceans
are now filled with uncountable trillions of tiny pellets of plas-
tic floating just under the surface like confetti (Figure 16.16b).
450 Some plastics sink, littering the bottom of the ocean where the

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