Algae as Bioindicators - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 103

Ta b l e 3 . 1 Main Features of Biomarkers and Bioindicators in the Assessment of Environmental Change.

Major Features Biomarkers Bioindicators

Types of response Subcellular, cellular Individual community

Primary indicator of Exposure Effects

Sensitivity to stressors High Low

Relationship to cause High Low

Response variability High Low

Specificity to stressors Moderate-high Low-moderate

Timescale of response Short Long

Ecological relevance Low High

Analysis requirement Immediate, on site Any time after collection (fixed sample)

Source : Adapted from Adams, 2005.

Single species

organic pollutants (e.g. pesticides), inorganic pollu-
tants (e.g. heavy metals), acidity and salinity. In an
ideal world, these would be measured routinely in all
water bodies being monitored, but constraints of cost
and time have led to the widespread application of
biological monitoring.
The advantages of biological monitoring over sep-
arate physicochemical measurements to assess water
quality are that it:

In general, a good indicator species should have the
following characteristics:
A narrow ecological range

Rapid response to environmental change

Well-defined taxonomy

Reliable identification, using routine laboratory
equipment

Reflects overall water quality, integrating the
effects of different stress factors over time; physic-
ochemical measurements provide information on
one point in time.

Wide geographic distribution

Combinations of species

Gives a direct measure of the ecological impact
of environmental parameters on the aquatic organ-
isms.

In almost all ecological situations it is the combina-
tion of different indicator species or groups that is
used to characterise water quality. Analysis of all or
part of the algal community is the basis for multivari-
ate analysis (Section 3.4.3), application of bioindices
(Sections 3.2.2 and 3.4.4) and use of phytopigments
as diagnostic markers (Section 3.5.2)

Provides a rapid, reliable and relatively inexpen-
sive way to record environmental conditions across
a number of sites.

Biological monitoring has been particularly use-
ful, for example, in implementing the European
UnionDirectiverelatingtosurfacewaterquality(94C
222/06, 10 August 1994), where Member States were
obliged to establish freshwater monitoring networks
by the end of 1998.

3.1.3 Biological monitoring versus chemical
measurements

In terms of chemistry, water quality includes inor-
ganic nutrients (particularly phosphates and nitrates),