- INTERTIDAL—where the ocean meets the land. Can be submerged or exposed
since waves and tides come in and out resulting in constantly changing
communities. On rocky coasts, the zone is stratified vertically. Only a few
species of algae and mollusks occur at high tide area with more diversity in
areas more frequently submerged, e.g., herbivorous snails, crabs, sea stars,
and small fishes. The intertidal zone on sandier shores is not as stratified as
in the rocky areas because waves keep mud and sand constantly moving,
preventing the establishment of algae and plants. Examples of organisms
living in this area of the intertidal zone include worms, clams, predatory
crustaceans, crabs, and shorebirds.
Organisms have evolved methods of not being swept away by waves and
preventing water loss during low tide through shells and exoskeletons, salt-
removing mechanisms, and lower metabolic rates due to cooler ambient
temperatures. - PELAGIC—open ocean. Thermal stratification with a constant mixing of
warm and cold ocean currents. Includes surface seaweeds, many species of
fish, and some mammals, such as whales and dolphins. Many organisms
feed on the abundant plankton.
Major Environmental Threats
■ Overfishing.
■ Coastal pollution (e.g., Deepwater Horizon oil spill).
■ Rising temperature of seawater, which dramatically affects corals
(bleaching) and sea nurseries, upwelling, and currents.
■ Increased acidification of seawater by increased atmospheric
concentrations of CO 2.
■ Introduction of invasive species through dumping ship ballast water and
the commercial worldwide aquarium trade (e.g., green crab, killer algae,
lion fish, and the zebra mussel).SOLUTIONS
– Take steps to reduce the effects of climate change, which affects the
ocean water temperature and pH, marine biodiversity, and coastal
inundation.
– Reduce the demand for overexploited marine species as food through