Phytoplankton an Introduction
Sadia tahir
phytoplankton
As the main primary producer, phytoplankton is an important link between the
physical and chemical elements and higher tropic levels in the marine food web
Changes in the environment could affect the annual succession and species
composition of the phytoplankton, as well as the overall primary production in
the area.
Phytoplankton monitoring will give important information regarding biological
changes on the lowest level in the food web with environmental impact and
climatic changes.
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Diatoms have rigid cell walls
consisting of two closely fitting
halves; they are like miniature
greenhouses, protecting internal
plant matter within glass walls.
These algae occur as single cells,
chains and colonies. Cell sizes
range from 5 to 1000 micrometers.
Centric diatoms have circular,
triangular, or pillbox shapes.
Pennate diatoms are elongate
with bilateral symmetry. Diatoms
may have spines or other
projections and some are toxic.
Diatoms
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Dinoflagellates are generally smaller than diatoms (can be as small
as 10 micrometers). They usually occur as single cells.
Typical dinoflagellate forms have a body surface with two grooves,
each having a "whip-like" flagellum they use to swim.
Some dinoflagellates are plant-like (get energy from the Sun), others
are animal-like (consume other organisms for energy), and some are
both.
There are bioluminescent dinoflagellates and toxic species, too.
lexandrium acatenella
(Whedon et Kofoid) Balech,
1985
Plate 1, Figs. 1-4
Species Overview: Alexandrium
acatenella is an armoured,
marine, planktonic
dinoflagellate. It is associated
with toxic PSP blooms in Pacific
coastal regions.
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This guidebook illustrates the morphology and taxonomy of harmful marine dinoflagellates of the
following genera:
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Coccolithophores surround themselves with plates made
of calcite. Known as coccoliths, these plates have a
variety of shapes.
Single coccolithophores are commonly smaller than 20
micrometers across and are often enclosed by over 30
plates.
Coccolithophores can form enormous blooms, turning
seas an opaque turquoise color.
The Black Sea ain't so black after all. This image, captured
by NASA's Aqua satellite, shows it in vibrant shades of cyan,
turquoise and blue. The swirling patterns on the surface of the
water are caused by blooms of microscopic plankton known as
coccolithophores.
coccolithophores
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These little single-celled organisms suck carbon from the
atmosphere, combining it with calcium and oxygen to form little
plates of calcium carbonate known as coccoliths. Something akin to
limestone bodysuits, they resemble floating hubcaps. When they die,
they slowly sink to the ocean floor, eventually being consumed and
excreted by other sea life.
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In this way, coccolithophores play a vital role in the ocean's
"biological pump". This is a part of the carbon cycle that transfers
carbon from the air into the ocean depths. Microscopic sea organisms
such as coccolithophores speed this up, lowering the concentrations
of carbon dioxide in the atmosphere as they calcify and sink into the
sediment.
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Phytoflagellates are diverse, crossing ten classes of algae. These
motile organisms are so small they must be identified using
powerful microscopes or biochemical techniques. Phytoflagellates
are very abundant and often dominate the phytoplankton when
larger forms -- i.e., diatoms and dinoflagellates -- are low in
concentration.
Pediastrum, a flat colony of green algae
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Photosynthetic bacteria are some of the smallest -- and largest-phytoplankton.
They exist as small single cells (less than 1 micrometer in diameter)
but some forms clump together to form "bundles" that can be seen by
eye.
Photosynthetic bacteria are major contributors to oceanic primary
productivity. One type, Prochlorococcus, may be the most abundant
species on earth.