Freshwater Algae: Identification and Use as Bioindicators

3.1 BIOINDICATORS AND WATER QUALITY 101Table 3.1ChangeMain Features of Biomarkers and Bioindicators in the Assessment of EnvironmentalMajor Features Biomarkers BioindicatorsTypes of response Subcellular, cellular Individual-communityPrimary indicator of Exposure EffectsSensitivity to stressors High LowRelationship to cause High LowResponse variability High LowSpecificity to stressors Moderate-high Low-moderateTimescale of response Short LongEcological relevance Low HighAnalysis requirement Immediate, on site Any time after collection (fixed sample)Adapted from Adams, 2005.to environmental change has been particularly useful,with the identification of particular indicator speciesor combinations of species being widely used in assessingwater quality.Single speciesIn general, a good indicator species should have thefollowing characteristics: a narrow ecological range rapid response to environmental change well defined taxonomy reliable identification, using routine laboratoryequipment wide geographic distribution.Combinations of speciesIn almost all ecological situations it is the combinationof different indicator species or groups that isused to characterize water quality. Analysis of all orpart of the algal community is the basis for multivariateanalysis (Section 3.4.3), application of bioindices(Sections 3.2.2 and 3.4.4) and use of phytopigmentsas diagnostic markers (Section 3.5.2)3.1.3 Biological monitoring versus chemicalmeasurementsIn terms of chemistry, water quality includes inorganicnutrients (particularly phosphates and nitrates),organic pollutants (e.g. pesticides), inorganic pollutants(e.g. heavy metals), acidity and salinity. In anideal world, these would be measured routinely in allwater bodies being monitored, but constraints of costand time have led to the widespread application ofbiological monitoring.The advantages of biological monitoring over separatephysicochemical measurements to assess waterquality are that it: reflects overall water quality, integrating the effectsof different stress factors over time; physicochemicalmeasurements provide information on one pointin time. gives a direct measure of the ecological impactof environmental parameters on the aquaticorganisms. provides a rapid, reliable and relatively inexpensiveway to record environmental conditions across anumber of sites.Biological monitoring has been particularly useful,for example, in implementing the European