Non-living (abiotic) factors that influence the patterns of ocean life
include:
Favorable physical and chemical enviornments,
Large scale circulation,
Near shore slopes,
Local tides, and
Storm events
Available sunlight
Nutrient Cycle
Most surface waters are deficient in nutrients and cannot sustain growth
unless upwelling resupplies nutrients.
The base of marine life is a large complex group of microscopic organisms
known as plankton. Plankton can be broadly divided into:
Phytoplankton - the plants or photosynthetic organisms,
Zooplankton - the animal component, and
Bacteria - decomposers of organic matter into its abiotic constituents.
Picoplankton
Nutrients, such as nitrogen and phosphorus, found mostly in colder
upwelled water are needed to fertilize phytoplankton that grow only
in near-surface waters of the ocean.
Phytoplankton (microscopic plants) is the principal source of food
supporting all animal life in the oceans. Phytoplankton is sometimes
referred to as the grass of the sea.
Fish population
density
and productivity are higher in the coastal
areas, especially in upwelling regions, than in the open ocean areas
where there is no upwelling.
Food Chain
Photosynthetic organisms are eaten by herbivorous zooplankton, which
are eaten by carnivores, which are eaten by large carnivores, and so
on. Each step in this food chain is a trophic level.
Seasonal Blooms
Intense blooms of phytoplankton occur naturally, but infrequently,
in many parts of the coastal oceans, particularly in temperate climates.
Intense blooms of dinoflagellates occur in some regions, especially
the tropics.
The frequency of such blooms appears to be increasing and
They are appearing in areas where they have not been seen before.
Dinoflagellate blooms can be caused by a variety of mechanisms:
Large increase in freshwater runoff which creates a shallow layer
of low-salinity water in a previously well-mixed water column.
Run-off that contains inorganic or organic compounds react with
toxic substances, such as copper and mercury, and reduces their
toxicity to phytoplankton.
The dense concentration of phytoplankton in bloom colors the surface
water yelllow, green, brown, or reddish, depending on the species. Many
dinoflagellates have a reddish color, so their blooms are called
red
tides.
Toxins produced by dinoflagellate blooms often kill large numbers of
fish.
Zones of the Ocean
The near-surface water layer, where there is light, and photosynthesis
is possible, is called the photic zone.
Life is found everywhere in the ocean--on the ocean floor, on the continental
slopes, and floating or swimming in the water. Life is found thousands
of meters deep in the ocean, far from the reach of sunlight. Special
types of life are found surrounding chimney-like vents that release
hot water rich with minerals.
The photic zone layer is where most marine life exists.
The depth of the photic zone layer is not constant because the angle
of the incoming sunlight varies from day to day and seasonally. The
photic zone extends to the seafloor in many areas of the coastal ocean.
Productivity is greatest in zones of high temperature gradients called
ocean fronts.
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