Freshwater Algae: Identification and Use as Bioindicators

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100 3 ALGAE AS BIOINDICATORSBIOMARKERSENVIRONMENTALMONITORINGBIOINDICATORSPECIESCompetitionsuccessReproductionGrowthweeks-yearsPhysiologicalBioenergeticsdays-weeksFigure 3.1 Hierarchical responsesof algae to environmental change,such as alterations in water quality.The time-response changes relateto sub-organismal (left), individual(middle) and population (right)aspects of the algal community. Environmentalmonitoring of the algalresponse can be carried out atthe biomarker or bioindicator specieslevel. Adapted from Adams (2005).BiochemicalBiomolecularENVIRONMENTALCHANGEseconds-daysand stimulation of phosphate transporters/reductionin alkaline phosphatase secretion (increased aquaticinorganic phosphate concentration).The time scale of perturbations in the algal communitythat results from environmental change (stress)can be expressed as a flow diagram (Fig. 3.1), withmonitoring of algal response being carried out eitherat the biomarker or bioindicator species level. Althoughthe rapid response of biomarkers potentiallyprovides an early warning system for monitoring environmentalchange (e.g. in water quality), the use ofbioindicators has a number of advantages (Table 3.1)including high ecological relevance and the ability toanalyse environmental samples (chemically-fixed) atany time after collection.3.1.2 Characteristics of bioindicatorsThe potential for freshwater organisms to reflectchanges in environmental conditions was first notedby Kolenati (1848) and Cohn (1853), who observedthat biota in polluted waters were different fromthose in non-polluted situations (quoted in Liebmann,1962).Since that time much detailed information hasaccumulated about the restrictions of different organisms(e.g. benthic macroinvertebrates, planktonicalgae, fishes, macrophytes) to particular types ofaquatic environment, and their potential to act as environmentalmonitors or bioindicators. Knowledge offreshwater algae that respond rapidly and predictably
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
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Freshwater Algae: Identification and Use as Bioindicators

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