1. Phytoplankton an Introduction
Sadia tahir

2. 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.

3. 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.

4. Diatoms 

5. 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.

7. lexandrium acatenella (Whedon et Kofoid) Balech, 1985 Plate 1, Figs
Species Overview: Alexandrium acatenella is an armoured, marine, planktonic dinoflagellate. It is associated with toxic PSP blooms in Pacific coastal regions.
This guidebook illustrates the morphology and taxonomy of harmful marine dinoflagellates of the following genera:

8. Coccolithophores surround themselves with plates made of calcite
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.

9. The Black Sea ain't so black after all
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.

10. coccolithophores
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.
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.

11. Phytoflagellates are diverse, crossing ten classes of algae
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

13. 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.