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On rocks and all exposed surfaces in streams grows a slimy substance called a Polysaccaride Matrix. It is also know as Biofilm. |  |
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Biofilm is a gel-like substance and is a mixture of sugars, enzymes, diatoms (attached and loose), bluegreen algae, bacteria, fungus, microinvertebrates, i.e., protozoans and early stages of insects. It absorbs Dissolved Organic Matter (DOM) from the water and collects Fine Particulate Matter (FPOM) in the matrix. |
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Diatoms commonly comprise the dominate algal group in river biofilms in terms of species number and biomass. Production is greatest in swift, well-lighted water where nutrients and oxygen are constantly replenished and direct sunlight is plentiful. |
