Microbial Communities

Microbial Communities

	Microbial Communities - In neutral and slightly alkaline waters of ponds and lakes, planktons are represented by the group diatoms which includes Fragilaria and Melosira varians. Acidic, oligotrophic lakes have flagellated planktons like Euglena and Chlamydomonas. Eutrophic lakes include planktons of the groups Chlorococcales such as Scenedesmus, Chlorella etc., Coccoid cyanophyta such as Microcystis and Coelosphaerium and filamentons cyanophyta such as Anabaena and Oscillatoria etc.
Epilithon Communities in lakes include diatoms, blue-green algae, desmids and bacteria which are usually embedded in mucilaginous matrix. Upper regions and near water regions are dominated by the cyanophyta such as Gloeocapsa, Nostoc, Calothrix, Rivularia etc. while submerged regions contain chlorophyta such as Spirogyra and Oedogonium. Epipelon communities in lakes and ponds are mostly of the group chlorophyta in which the examples are Spirogyra and Zygonema. Bacterial numbers in muds are in the order of 104 to 106 per gram of dry weight near the surface and the numbers decrease when going deep into the sediments.
Among many bacteria active in the sediment of lakes species of Desulfovibrio, which reduce sulfate ions to sulfide ions, are common. Other members of bacteria anaerobically decompose settled organic material. For instance Methanobacterium and Methanococcus produce methane from organic substances. Actinomycetes, especially which produce dry spores, such as Nocardia, Streptomyces and Micromonospora are quite common in eutrophic lakes. Yeasts with branched group of cells, are also found on debris. Common example is Candida aquatica. Fungi are generally represented by Pythium and Fusarium.

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