Freshwater Algae: Identification and Use as Bioindicators

3.2 LAKES 115Table 3.5 Organic Pollution: Most Tolerant Algal Genera and Species (Palmer, 1969)No. Taxon ClassPollutionIndexFreshwater HabitatGenus1 Euglena Eu 5 Planktonic2 Oscillatoria Cy 5 Planktonic or benthic3 Chlamydomonas Ch 4 Planktonic4 Scenedesmus Ch 4 Planktonic5 Chlorella Ch 3 Planktonic6 Nitzschia Ba 3 Benthic or planktonic7 Navicula Ba 3 Benthic8 Stigeoclonium Ch 2 Attached9 Synedra Ba 2 Planktonic and epiphyticspecies10 Ankistrodesmus Ch 2 PlanktonicSpecies1 Euglena viridis Eu 6 Ponds and shallow lakes2 Nitzschia palea Ba 5 Lakes and rivers3 Oscillatoria limosa Cy 4 Stagnant or standing waters4 Scenedesmus quadricauda Ch 4 Lake phytoplankton5 Oscillatoria tenuis Cy 4 Ponds and shallow pools6 Stigeoclonium tenue Ch 3 Epiphyte, shallow waters7 Synedra ulna Ba 3 Lake phytoplankton8 Ankistrodesmus falcatus Ch 3 Lake phytoplankton9 Pandorina morum Ch 3 Lake phytoplankton10 Oscillatoria chlorina Cy 2 Stagnant or standing watersTen most tolerant algal genera and species. listed (Palmer, 1969) in order of decreasing tolerance. Algalphyla: Cyanophyta (Cy), Chlorophyta (Ch), Euglenophyta (Eu) and Bacillariophyta (Ba).Pollution index – see text.pollution was originally pioneered by Kolkwitz andMarsson (1908).Palmer (1969) carried out an extensive literaturesurvey to assess the tolerance of algal species to organicpollution, and to incorporate the data into anorganic pollution index for rating water quality. Algalgenera and species were listed separately in orderof their pollution tolerance (Table 3.5), and includeda wide range of taxa (euglenoids, blue-greens, greenalgae and diatoms) as well as planktonic and benthicforms. The assessment of genera was determined asthe average of all recorded species within the genus,and is perhaps less useful than the species rating –where single, readily identifiable taxa can be directlyrelated to pollution level.The species organic pollution index developed byPalmer uses the top 20 algae in the species list (top10 shown in Table 3.5). Algal species are rated on ascale 1 to 5 (intolerant to tolerant) and the index issimply calculated by summing up the scores of allrelevant taxa present within the sample. In analysingthe water sample, all of the 20 species are recorded,and an alga is considered to be ‘present’ if there are50 or more individuals per litre.Examples of environmental scores are given in Table3.6, with values of >20 consistent with high organicpollution and