Aquatic ecology and Biodiversity

Unit 7- Biotic communities

7.2. Phytoplankton
The phytoplankton is principal source of primary nutrition. Phytoplankton produces organic matter through the process of photosynthesis. They contribute to about 95% of primary production in the oceans and it supports the secondary production (zooplankton) and tertiary production (fish, shellfish, mammals, etc.). About 5,000 phytoplankton have been identified in aquatic ecosystem.
Diatoms
Common forms of centric diatoms are Coscinodiscus, Chaetoceros, Biddulphia, Skeletonemia, Thallassionema, and Bacteriastrum, Thalassiosira, Navicula, Triceratium. Some common pennate diatoms are Pleurosigma, Gyrosigma, Rhizosolenia, Thalassiothrix, Thalassionema and Nitzschia

Dinoflagellates
Dinoflagellates are next to diatoms in importance both in number and abundance of species. They are abundant in trophical water producing red tides. Among dinoflagellates, the genera of Peridinium and Ceratium are most commen in the plankton. Common unarmored (“naked”) representatives of dinoflagellates are Gymnodinium, Cystidinium, and Glenodinium. Whereas common armored dinoflagellate species are Peridinium, Ceratium, Dinophysis, and Goniaulax etc. Non-photosynthetic species is. Noctiluca. Sp. Certain species produce a poison – PSP. The well known red tide is caused by Goniaulax sp. and Gymnodinium brevis. Noctiluca scintillans exhibit bioluminescence
Coccolithophores
Coccolithophores are one-celled marine plants that live in large numbers in the upper layers of the ocean. Coccoliths are particularly abundant in the sub-trophical areas and also live in most subpolar regions. Importatent forms are Dicrateria, Phaeocystis, Coccolithus, Prymnesium etc.

Silicoflagallates
Phytoflagellates are algae. They are abundant in phytoplankton Important forms of silicoflagellates are Dictyoche, Distephanus, Chromulina etc.

Blue-green algae

Trichodesmium sp
The blue-green algae are the hard, simple algae. The blue-greens are widely distributed over land and water. They were the chief primary producers of organic matter. Trichodesmium sp species are tropical, dominant in warm seas and forms blooms.
Green algae

The green algae are unicellular and colonial flagellates, often colonial, commonly found in fresh water.