Freshwater Algae: Identification and Use as Bioindicators

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132 3 ALGAE AS BIOINDICATORSBiofilm studies by Rimet et al. (2005), showed thatsome indices (e.g. CEE, TDI – high sensitivity) respondedmore rapidly than others (GDI, ILM, SLA –intermediate sensitivity) to environmental change.All indices showed significant change (integrationinterval) within 40–60 days of biofilm transfer.Standardization of approachThe above studies indicate that benthic diatoms providethe basis for a standard approach to river monitoring,able to be used as an alternative (or addition) tomacroinvertebrate sampling. Individual commonlyuseddiatom indices appear to correlate significantlywith macroinvertebrate data, and also with each other(see above). Studies by Kelly et al.(1995) have alsoshown that benthic diatom indices do not changesignificantly either with season or with major flowevents (both of which can influence invertebrate populations)– suggesting that diatom indices are robustand that consistent results can be obtained throughoutthe year.Standard procedures are important in ensuringcomparability of results. These include standardizationof sampling procedures (Kelly et al., 1998),adoption of analyst quality controls (see below), accessto common data bases and use of comparablediatom indices.Access to common databases Access to webbaseddata sites such as the European DiatomDatabase Initiative (EDDI) promotes a standard approachto identification, data acquisition and manipulation.Although this site has particularly applicationfor palaeolimnology (Section 3.2.2), other databasesspecifically on benthic diatoms (Gosselain et al.,2005) may be more applicable to river studies.Comparable diatom indices Although a singlediatom index (coupled with the identification of keydiatom indicator taxa) would be adequate for environmentalmonitoring, the trend is for diatom countsto be fed into a database for determination of multipleindices. The general availability of the OMNIDIAdatabase software (Lecointe et al., 1993), incorporatingindices summarized in Table 3.14, is particularlyuseful in this respect.The indices contained in the OMNIDIA softwareare based on European diatom communities andclearly apply most directly to European rivers. Applicationof this software in other parts of the world requiresthe incorporation of local (endemic) species, asemphasized by Taylor et al. (2007) in their studies onSouth African rivers. It is also important to check thatcosmopolitan species have similar ecological preferencesin different parts of the world. Dela-Cruz et al.(2006), for example, assessed the suitability of ‘northernhemisphere’ ecological tolerance/preference datafor periphytic diatoms in south-eastern Australianrivers before using bioindicator indices.Quality assuranceAlthough techniques for standardized sampling of diatoms(Section 2.10.1), and different types of indices(Section 3.4.5) are well defined, the final environmentalassessment ultimately depends on the analyst’sability to accurately record species compositionfrom the environmental samples. Quality assessmentof analyst performance is important, since regulatoryagencies must be confident that data produced by theirstaff are relevant and accurate. In Europe, for example,the requirement of water companies to install nutrientremoval facilities in certain large sewage treatmentworks (Urban Wastewater Treatment Directive– European Community, 1991) is determined by assessmentof water quality and is highly expensive.The use of benthic diatoms in the implementation ofthis directive (Kelly, 2002) must be reliable.In the case of chemical analyses of water quality(including soluble nitrates and phosphates) thesituation is relatively simple, since chemical parametersare relatively few, with comparisons that areunivariate and amenable to conventional parametricstatistics. In contrast to this, biological monitoring ismore complex – based on field samples containingmany species, all of which may contribute to the assessment.These species counts may be assessed aspresence/absence or in terms of relative abundance. Presence/absence. Invertebrate analyses in theUnited Kingdom are carried out on this basis,with water quality being determined in relation tothe presence/absence of key benthic invertebratedata (Mason, 1996). Reliability of assessment by
individual analysts can be measured as a ‘qualityaudit,’ where the number of taxa ‘missed’ byan (inexperienced) analyst can be compared to thesample assessment by an experienced auditor. Relative abundance. A more complicated situationis presented by diatom-based monitoring, wherethe relative abundance of taxa, rather than theirpresence or absence, is being recorded. In this situation,comparison of analyses by different analystscan be carried out on the basis of ‘similarity measures’.The higher the value of the ‘measure’ thegreater the similarity, rising to a point at whichthe two sets of data can be considered derived fromthe same population.3.5 ESTUARIES 133Kelly (2001) has used the ‘Bray–Curtis similaritymeasure’ to assess analyst performance, with levels of>60% indicating good agreement between primaryanalyst and auditor. Evaluation of about 60 comparisonsshowed that reliability of assessment variedwith species diversity, and that samples with largenumbers of species had lower levels of similaritycompared to those with low numbers. The use of suchan audit measure, providing an objective measure ofanalyst performance, has clear application within regulatoryorganizations such as Water Authorities.3.5 EstuariesEstuaries are aquatic zones that interface betweenfreshwater rivers and saline seas. As such, they tendto be dominated by saltwater conditions, but also havemajor freshwater inputs. Algae have been widely usedas bioindicators of environmental change (Bortone,2005) in these highly complex aquatic systems.3.5.1 Ecosystem complexityEstuaries are highly complex ecosystems in relationto habitats, hydrology, effects of weather, constituentorganisms and human activity.HabitatsEstuaries can be divided into two main regions – acentral river drainage channel (or channels) and aFigure 3.8 View across the Mersey Estuary (UnitedKingdom) at low tide, showing the extensive mudflatswith main river channel in the distance. Freshwaterdrainage into the mudflats (foreground), with saltwaterflooding at high tides, leads to complex localizedvariations in salinity and nutrient concentrations. Someepipelic diatoms (present in surface biofilms) have widetolerances to variations in water quality while others haveclear environmental preferences (see text).surrounding expanse of mudflats (Fig. 3.8). Majorpopulations of phytoplankton are present within thedrainage channel, and an extensive biofilm of euglenoids,diatoms and filamentous blue-greens canoccur across the surface of the mudflats (Underwoodand Kromkamp, 1999). In addition minor drainagechannels also discharge freshwater into the mudflats/mainchannel (Fig. 3.8) and freshwater/salinewetlands are also frequently associated with the mainestuarine system.In many estuaries, water from the catchment areaalso has a major influence on the local marine environment,flowing as a freshwater plume into thesurrounding ocean.HydrologyPatterns of water circulation are complex. Watermovements within the main channel depend on input
Page 1 and 2: 3Algae as BioindicatorsBiological i
Page 3 and 4: 3.1 BIOINDICATORS AND WATER QUALITY
Page 5 and 6: Table 3.3 Lake Trophic Status: Phyt
Page 8 and 9: 106 3 ALGAE AS BIOINDICATORSDirecti
Page 11 and 12: 3.2 LAKES 109sites (Fig. 3.3 A, B,
Page 13 and 14: 3.2 LAKES 111Phytoplankton net prod
Page 15 and 16: 3.2 LAKES 113and hypertrophic (Pedi
Page 17 and 18: 3.2 LAKES 115Table 3.5 Organic Poll
Page 19 and 20: 3.2 LAKES 117Table 3.7 Bioindicator
Page 21 and 22: 3.3 WETLANDS 119therefore directly
Page 23 and 24: 3.4 RIVERS 1213.4 RiversUntil recen
Page 25 and 26: 3.4 RIVERS 123Gomphonema parvulum t
Page 27 and 28: 3.4 RIVERS 125Table 3.10 Benthic Di
Page 29 and 30: 3.4 RIVERS 127Palmer’s Index (Pal
Page 31 and 32: 3.4 RIVERS 129any irregular conclus
Page 33: 3.4 RIVERS 131Case study 3.3Compari
Page 37 and 38: 3.5 ESTUARIES 135potential role of

Freshwater Algae: Identification and Use as Bioindicators

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