Algae as Bioindicators - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 102

ENVIRONMENTAL
MONITORING

BIOINDICATOR
SPECIES

BIOMARKERS

Competition
success

Growth

Reproduction

weeks-years

Bioenergetics

Physiological

days-weeks

Figure 3.1 Hierarchical responses
of algae to environmental change,
such as alterations in water qual-
ity. The time-response changes relate
to sub-organismal (left), individ-
ual (middle) and population (right)
aspects of the algal community. Envi-
ronmental monitoring of the algal
response can be carried out at the
biomarker or bioindicator species
level. Adapted from Adams, 2005.

Biochemical

Biomolecular

seconds-days

ENVIRONMENTAL
CHANGE

irradiation, exposure to heavy metals), osmotic shock
(increased salinity), stimulation of nitrate and nitrite
reductase (increased aquatic nitrate concentration)
and stimulation of phosphate transporters/reduction
in alkaline phosphatase secretion (increased aquatic
inorganic phosphate concentration).
The timescale of perturbations in the algal commu-
nity that results from environmental change (stress)
can be expressed as a flow diagram (Fig. 3.1),
with monitoring of algal response being carried
out either at the biomarker or at the bioindica-
tor species level. Although the rapid response of
biomarkers potentially provides an early warning
system for monitoring environmental change (e.g.
in water quality), the use of bioindicators has a
number of advantages (Table 3.1) including high eco-
logical relevance and the ability to analyse environ-
mental samples (chemically fixed) at any time after
collection.

3.1.2 Characteristics of bioindicators

The potential for freshwater organisms to reflect
changes in environmental conditions was first noted
by Kolenati (1848) and Cohn (1853), who observed
that biota in polluted waters were different from
those in non-polluted situations (quoted in Liebmann,
1962).
Since that time much detailed information has
accumulated about the restrictions of different organ-
isms (e.g. benthic macroinvertebrates, planktonic
algae, fishes, macrophytes) to particular types of
aquaticenvironment,andtheirpotentialtoactasenvi-
ronmental monitors or bioindicators. Knowledge of
freshwater algae that respond rapidly and predictably
to environmental change has been particularly useful,
with the identification of particular indicator species
or combinations of species being widely used in
assessing water quality.