Environmental Engineering Reference
In-Depth Information
Fig. 2.7
Common brackishwater phytoplankton with unique shape and conguration
planktonic through out the life cycle are as follows:
(1) diatoms, (2) dino
diatoms. The major differences between these
two groups are given in Table
2.1
.
agellates, (3) coccolitho-
phores, (4) selective species of blue-green algae
and (5) some species of green algae. The members
of phytoplankton community have unique size,
shape and morphological features (Fig.
2.7
).
fl
Dinoflagellates
These are important producers of the marine
environment and rank second in importance in
the economy of the sea. Typically, these are
unicellular; some are naked, while others are
armoured with plates of cellulose. The dinoflag-
ellates possess
Diatoms
These
oating plants are all microscopic in size
and are characterized by the presence of shell or
frustule. The shell or frustule is composed of
translucent silica. The cell wall of diatom has two
parts resembling a pillbox bottom and lid. The lid
is called the
Epitheca
and the bottom is known
as
hypotheca
. These shells have great impor-
tance from the geological point of view and
constitute the diatomaceous crust. The diatoms
exhibit remarkable varieties and forms and many
species possess beautifully sculptured shells.
Examples of diatoms are
fl
agella for locomotion.
Several of them are luminescent and produce
light.
two
fl
Prorocentrum
sp. and
Ceratium trichoc-
eros
are two common dino
fl
agellates of marine
and estuarine waters.
Coccolithophores
These are among the smallest category of phy-
toplankton having a size range between 5 and
20
Skeletonema costatum
agella,
while others are devoid of them. Their soft
bodies are shielded by tiny, calci
ยต
m. Some coccolithophores have
fl
and
.
Depending on the nature of valves and pattern
of ornamentation in the valve surface, the dia-
toms are grouped into
centric
and
pennate
Coscinodiscus eccentricus
ed circular
plates or shields of various designs. These are
normally found in the open sea, but their profuse
