Environmental Engineering Reference
In-Depth Information
3
Algae as Bioindicators
Biological indicators (bioindicators) may be defined
as particular species or communities, which, by their
presence, provide information on the surrounding
physical and/or chemical environment at a particular
site. In addition to the diagnostic presence of indi-
cator species, cell size may also be used to monitor
environmental conditions in lakes (Fig. 3.7) and wet-
lands (Section 3.3).
In this topic, bioindicator algae are considered par-
ticularly in relation to aquatic chemistry or 'water
quality'. The basis of individual species as bioindi-
cators lies in their preference for (or tolerance of)
particular habitats, plus their ability to grow and out-
compete other algae under particular conditions of
water quality. Ecological preferences and bioindica-
tor potential of particular algal phyla are discussed in
Chapter 1. This chapter considers water quality mon-
itoring and algal bioindicators from an environmental
perspective, dealing initially with general aspects of
algae as bioindicators and then specifically with algae
in the four main freshwater systems - lakes, wetlands,
rivers and estuaries.
blue-green alga Microcystis is indicative of pre-
existing high-nutrient (eutrophic) status.
Short-term information, environmental change.
In a separate lake situation, detection of a change in
subsequentyearsfromlowtohighblue-greendom-
inance (with increased algal biomass) may indi-
cate a change to eutrophic status. This may be
an adverse transition (possibly caused by human
activity) that requires changes in management
practice and lake restoration.
In the context of change, bioindicators can thus
serve as early-warning markers that reflect the
'health' status of an aquatic system.
3.1.1 Biomarkers and bioindicators
In the above example, environmental change (to
a eutrophic state) is caused by an environmental
stress factor - in this case the influx of inorganic
nutrients into a previously low-nutrient system. The
resulting loss or dominance of particular bioindica-
tor species is preceeded by biochemical and phys-
iological changes in the algal community referred
to as 'biomarkers'. These may be defined (Adams,
2005) as short-term indicators of exposure to envi-
ronmental stress, usually expressed at suborganis-
mal levels - including biomolecular, biochemical and
physiological responses. Examples of algal biomark-
ers include DNA damage (caused by high UV
3.1
Bioindicators and water quality
Freshwater algae provide two main types of informa-
tion about water quality:
Long-term information, the status quo .Inthe
case of a temperate lake, for example, detec-
tion of an intense summer bloom of the colonial
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