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Zonation
of the Marine Environment
Global
Seafloor Topography
The abbyssal plains are not only
flat plains but exhibit deep-sea mounts and long ridges of midoceanic ridges.
The global topography of the sea floor became only known after special
techniques of satellite measurements were made possible in the late 1990's.
Classification
of the Marine Environment
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Classification
by light
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Photic
and aphotic
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Phytoplankton
need light to photosynthesize and can only thrive in the photic zone
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Zooplankton
(animals) and bacteria do not need light and inhabit the oceans down to
the deep-sea floor
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Classification
by location
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Water
and sea floor divided into specific zones: benthic & pelagic
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By water
depth divided into coastal, neritic, oceanic
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Each
has distinct physical and chemical characteristics
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Each
supports different organisms
Inhabitants
of Zones
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Plankton
(Pelagial)
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Floaters
and drifters, have to move with water currents
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Plants
and animals and protists and bacteria (free, attached); range from microscopic
size to several meters in length (jellyfish)
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Plants
and photosynthetic cyanobacteria = phytoplankton Animals = zooplankton;
bacteria = bacterioplankton
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Also
differentiation according to size: pico-, nano-, micro-, meso-, macro-,
megaplankton. Size does NOT separate plankton from nekton
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Nekton
(Pelagial)
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Free
swimmers, can overcome currents and move against them
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Animals
(large crustaceans, fish, mammals)
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Benthos
(Benthal)
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Attached
to, on, or in the sea floor
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Plants
and animals and protists and bacteria (range from microscopic size to several
meters in length (kelps)
Size Scale for Plankton
The discovery of very small (<2 µm) cyanobacteria as ubiquitous and
abundant inhabitants of the oceans between 1979 and 1989 led to extending
the size range of phytoplankton into the picoplankton size range. We know
today that the picoplanktonic phytoplankton is a major component in all
warm-water marine systems, and their discovery changed our perception of
marine food webs substantially. Phytoplankton occurs in three size classes:
--
picoplankton: 0.2 - 2.0 µm
--
nanoplankton: 2 - 20 µm
--
microplankton: 20 - 200 µm
Living
on the fast lane?
r-
and k- selection
r
– strategists
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Opportunistic
species
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In variable
or new environment
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Small
size, fast growth
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Early
mature, many reproduction cycles per season
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Many offspring
with high mortality rate and little care
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High motility
and dispersal
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Life span
short
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Low competitive
ability, thrive often in new environments
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K
- strategists
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Equilibrium
or capacity species
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Stable
environments
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Large
size, slow growth
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Late mature,
one or few repro- duction cycles per season
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Few offspring
with low mortal- ity and care taking of young
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Low dispersal,
territorial adults
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Life span
long
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High competitive
ability, out- compete r-strategists on long run
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