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Lesson N°8 :
Ocean Habitats and Their Biota
Biology of the continental shelf :
The fertile waters of the continental shelves ,the neritic zone , support a
rich community of organisms . Plankton include countless species of
microscopic plants and animals , as well as the eggs and larvae of many
benthic and nekton species . In contrast to the diverse planktonic
organisms , the nekton of
the neritic zone are dominated
overwhelmingly by fish . The shelf bottom , the sublittoral zone , is
occupied by diverse groups of benthic organisms that vary with changes
in the bathymetry and sediment cover of the sea bed .
Neritic Zone :
The predominant phytoplankton in shelf waters are species of diatoms
and dinoflagellates . Seasonal changes in water temperature , salinity
and nutrient input produce a regular succession of phytoplankton species
in temperate and polar seas.
Zooplankton , which are more diverse in neritic water than are
phytoplankton , are dominated by arthopods , particularly species of
copepods .
Plankton , whether they be plants or animals , are rarely distributed
evenly in space . Rather they tend to be aggregated into relatively
dense clusters. This uneven distribution is termed patchiness.
Unlike the plankton , which are at the mercy of currents , the nekton are
active swimmers . They are able to wander from spot to spot , avoiding
unfavorable water and searching for appropriate feeding and breeding
grounds. But , like the plankton , many species of fish cluster in groups
called schools , a habit that gives them , too , a patchy distribution .
In these compact groupings of fish , each member is the same size and
maintains a remarkably fixed three-dimensional spacing in conjunction
with its neighbors.
The entire school swims as a unit , executing precise maneuvers
faultlessly as if it were one large organism. No true leaders exist. In fact