Download CHAPTER 13 OCEAN HABITATS AND THEIR BIOTA

Ocean Habitats and
their Biota
13-1
Biology of the Continental Shelf
The waters of the neritic zone are
fertile and support a rich community
of organisms.
• The plankton are floaters and weak
swimmers which are helplessly transported
by ocean currents.
• Nekton have the ability to swim against
currents and actively search for a more
hospitable environment.
• Many fish display schooling, another form of
patchiness.
13-1
Biology of the Continental Shelf
Because the water column is shallow
in the sublittoral zone, physical
factors regulate the number, type and
distribution of benthic organisms.
• Bottom energy is a function of wave energy
and tidal currents and these vary inversely
with depth.
• The sea floor can be divided into two areas
based upon the energy of the environment:
High energy environments and Low energy
environments.
• Bottom energy affects organisms by: moving
sediment about and creating an unstable
substrate, controlling sediment size.
• Bottom sediment strongly influences the
feeding mode of benthic communities.
13-1
Biology of the Continental Shelf
• The two major benthic communities based
upon substrate are: Hard-bottom community
and Soft-bottom community
13-2
Biology of the Open Ocean and
the Deep Sea
The open ocean is the largest habitat
on Earth, but life is sparse because
of low nutrient concentration and
great depth.
• In the open ocean, diversity is high but the
number of individual per species is low.
• The only seaweed in the open ocean sea is
sargassum gulfweed.
• The major phytoplankton are diatoms,
dinoflagellates and coccolithophores and the
major zooplankton are foraminifera and
radiolaria.
• Diatoms dominate the shallow coasts, but decrease in
abundance seaward.
• Top predators are mackerel, squid, jellyfish,
tuna, porpoise, shark and man.
13-2
Biology of the Open Ocean and
the Deep Sea
• In the dysphotic zone, seasonal heating is
minimal and conditions tend to be uniform
most of the year.
• The aphotic zone is an area of permanent
darkness and cold.
13-2
Biology of the Open Ocean and
the Deep Sea
The biomass on the sea floor tends to
decrease with depth faster than it
does with distance from shore.
• The benthic food chains largely depend upon
food from the surface which reaches the
bottom.
• Characteristics of the benthic organisms
include: year-round reproduction, smaller
broods, slow growth, and longer life.
• Diversity of the benthos is greater than
expected because the high predation rate
prevents any group from dominating through
competitive exclusion (when one group outcompetes most others and drives them to
extinction).
13-2
Biology of the Open Ocean and
the Deep Sea
• Four traits common to all abyssal depths are:
perpetual darkness., low temperature, high
hydrostatic pressure, and sparse food
supply.
• Rate of bacterial decay is greatly reduced
under high hydrostatic pressure.
• This means that organic material that settles onto the
sea floor remains for a long time before it decays and
is thus more likely to be consumed.