Taxonomy and Saprobic Valency of Benthic Phytomicro-organisms

Role of diatoms as indicators of pollution gradients

The impact of liquid wastes from a paper mill on the benthic diatoms in flowing waters has been studied for a period of two years. Water and algal samples were analysed at monthly intervals at three sites along the course of the river, along with raw effluents. The water before the confluence of effluents was well oxygenated with an alkaline pH. Organic matter, NH3 and nutrients were recorded at low concentrations. At the entry of effluents, the water showed considerable decline in dissolved oxygen content, increase in organic matter, hardness, Cl, HCO3 and total dissolved solids. Diatoms constituted 61% by numerical abundance and were reduced to 25% of total algae at the entry of effluents. Multiple regression analysis was employed to discover the relative importance of various physicochemical variables on the abundance and distribution of diatoms at various sampling stations. Mathematical equations were derived involving the physicochemical variables for better prediction of algal number.

A COMPOSITE RATING OF ALGAE TOLERATING ORGANIC POLLUTION(2)

From information on pollution-tolerant algae compiled from reports from 165 authors, the genera and species most often referred to as significant fall into a relatively stable series. Diatoms, pigmented flagellates, green, and blue-green algae are all well represented among the pollution-tolerant genera and species. The top 8 genera are Euglena, Oscillatoria, Chlamydomonas, Scenedesmus, Chlorella, Nitzschia, Navicula, and Stigeoclonium, and the top 5 species, Euglena viridis, Nitzschia palea, Oscillatoria limosa, Scenedesmus quadricauda, and Oscillatoria tennis. In some genera, e.g., Euglena, a single species is far more significant than all others as a pollution-tolerant form. In other genera, e.g., Oscillatoria, only a slight difference distinguishes the pollution tolerance of 2 or more species. Algal genus and species pollution indices arc presented for use in rating water samples with high organic pollution.