Freshwater Algae: Identification and Use as Bioindicators

3.4 RIVERS 125Table 3.10 Benthic Diatom Community Analysis of Finnish Rivers (Soininen et al., 2004) Showing Some of theMajor Community GroupsGroup Ecoregion Stream Water Quality Characteristic TaxaA Eastern Finland Polyhumic, acid Eunotia rhomboideaEunotia exiguaB Eastern Finland, woodland Oligotrophic, neutral Fragilaria construens,Gomphonema exilissimumGomphonema gragileAchnanthes linearisAulacoseira italica*Rhizosolenia longiseta*C South Finland, small foreststreamsSlightly acid, low conductivity,humicD South Finland ConnectlakesE Mid-boreal Mesotrophic, neutral, humic Achnanthes bioretiiAulacoseira subarcticaF North boreal Oligotrophic, clear water, neutral Caloneis tenuisGomphonema clavatumH Arctic-alpine Achnanthes kryophilaEunotia arcusJ South Finland, many smalllakes and pondsPolluted: eutrophic, high organiccontentK South Finland Polluted: eutrophic – treatedsewage, diffuse agriculturalloading*Planktonic diatoms. Groups A–K selected from 13 ecoregions.Aulacoseira ambigua*Cyclotella meneghiniana*Motile biraphid species – e.g.Surirella brebissoniiNitzschia pusillaactually meant by a natural original community. Thisis evident in the studies of Eloranta and Soininen(2002) on Finnish rivers, for example, where diatomspecies composition of undisturbed benthic communitiesvaried with river substrate, turbidity and localhydrology (Table 3.11).In an objective assessment of human impact onnatural communities, Tison et al. (2005) analysed836 diatom samples from sites throughout the Frenchhydrosystem using an unsupervised neural network,the self-organizing map. Eleven different communitieswere identified, five corresponding to naturalTable 3.11 Diatom Adaptations to Local Environmental Conditions in Finnish Rivers(Eloranta and Soininen, 2002)EnvironmentSubstrateHard substratesSoft substratesTurbidityClear watersClay-turbid watersHydrologyLake and pond inflowsTypical DiatomsAttached epilithic and epiphytic taxaPinnularia, Navicula and NitzschiaAchnanthesSurirrella ovalis, Melosira varians and Navicula spp.Aulacoseira spp., Cyclotella spp. and Diatoma tenuis