The phytoplankton are mainly unicellular plants known as algae.
They are found dispersed throughout the
photic zone of the oceans and account for the major share of primary productivity in the marine environment.
The most important phytoplankton that are presently recognized are those 2-20
m in size, which are classified
The major nannoplankton size groups in the oceans are the diatoms and the
dinoflagellates, both unicellular forms of phytoplankton.
These organisms may or may not be visible with light
Please use the enclosed black and white photographs to assist in identifications.
occur as single cells or in chains or other loose aggregates
2. cell sizes can range 15
m - 1000
m, although most diatom sizes range from 50 to 500
3. presence of a porous, rigid cell wall (frustule) made mostly of silica and consisting of two closely fitting
halves (epitheca and hypotheca)
4. presence of many small chloroplasts
5. occur in varied shapes: circular, triangular, and modified square shapes are known as centric diatoms
(shaped like pillboxes), whereas the elongated ones (bilateral symmetry) are termed pennate diatoms
6. may possess spines or other projections that increase their surface area
7. some common representatives of centric diatoms:
Some common pennate diatoms are
occur as single cells, rarely in chains or other aggregates
2. cell sizes range from 25 to 1000
m, generally smaller than diatoms
3. presence of a porous cell wall made mostly of cellulose.
In some armored forms, the cell wall consists of
many articulating cellulose plates arranged irregularly over the cell surface
most possess several small chloroplasts usually located near the cell ends
(a few species are not photosynthetic)
5. typical forms have a body surface with two grooves, each having a flagellum
6. may possess spines, horns or other projections
7. some common unarmored (“naked”) representatives:
Some common armored species are