Earth Science
Chapter 14
Section 2
A. Life at the Ocean’s Edge:
Living conditions:
Some physical factors that determine where marine organisms
can live include salinity, water temperature, light dissolved
gases, nutrients and wave action.
On land, most organisms live on or near the surface. The
ocean, on the other hand, is a three-dimensional environment.
Organisms inhabit it at every depth.
Scientists classify marine organisms according to where they
live and how they move.
Plankton are tiny algae and animals that float in the water and
are carried by waves and currents. Algae plankton, include
geometrically shaped diatoms. Animal plankton, include
microscopic crustaceans and fish larvae.
Nekton are free-swimming animals that can move throughout
the water column. Octopus and squid, most fishes, and marine
mammals such as whales and dolphins are nekton.
Benthos are organisms that inhabit the ocean floor. Some
benthos, like crabs, sea stars and lobsters can move from place
to place. Others, like sponges and sea anemones, stay in one
location.
Many plankton and benthos are algae they make their own food
through photosynthesis.
Other plankton, benthos and some nekton are consumers.
They eat algae and other consumers.
Finally, some other organisms and many benthos are
decomposers. They break down waste and remains of other
organisms.
These feeding relationships in a habitat make up a food web.
B. Rocky Shores:
Intertidal Zone- stretches from the highest high-tide line on
land to the point on the continental shelf exposed by the lowest
low tide.
Organisms that live in the rocky intertidal zone must be able to
tolerate the pounding wave and changes in salinity and
temperature. They must also withstand periods of being
underwater and periods of being exposed to the air.
Along the rocks:
The highest rocks, above the highest high tide line makes up
the spray zone. This area gets wet when waves break against
the rocks.
A stripe of black algae indicates the highest high-tide line.
The rocks below this level are covered with barnacles.
Lower down, clumps of blue and black mussels stick out
among the algae.
The rocks are also home to flat mollusks called limpets.
Limpets have a large muscular foot to hold onto rocks tightly.
In Tide Pools:
When the tide goes out some water remains in depressions
among the rocks called tide pools.
Organisms in the tide pools must be able to withstand changes
in temperature and salinity.
Tide pool creatures include:
Sea stars
Sea urchins
Sponges
Sea anemones
C. Where Rivers Meet Oceans:
Other important environments along the ocean’s edge are
estuaries.
Estuaries are coastal inlets or bays where fresh water from
rivers mixes with the salty ocean water.
Water that is partly salty and partly fresh is brackish.
Coastal wetlands are habitats found in and around estuaries.
Along the U.S. coast, most coastal wetlands are either salt
marshes or mangrove forests.
Salt Marshes – have muddy soil that is rich in nutrients, and
the dominant plant is cord grass. Tidal channels running
through the grass break up waves, which protect organisms
from the ocean surf.
Mangrove forest – have arching prop roots that anchor the
trees to the land. These roots break up wind and waves,
protecting the land and organisms that live there. The roots
also trap sediment so the water is rich in nutrients.
Protecting Estuaries:
Harmful materials carried there by the river can pollute an
estuary. These pollutants- including pesticides, sewage and
industrial wastes- affect the organisms that live in the
estuary.
If the river is cleaned up, ocean tides can flush the pollutants
out of the estuary.