Environmental Engineering Reference
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also with parameters of water quality - organic load (BOD), oxygen concentration, conductivity, measured
ion concentrations and trophic level (NH 4 -N, PO 4 -P). Two particular indices - IPS and GDI - gave the best
environmental resolution in terms of correlation with water quality variables (see Table 3.6) and showing clear
differences between the separate river groups.
Although the diatom indicator system emerged as a useful tool to evaluate general water quality, some
indices were not able to differentiate between adverse effects of eutrophication (inorganic nutrients) and
organic material pollution. Abundance of key indicator species, however, such as A. minutissima (highly
sensitive towards organic pollution) and Amphorapediculus (eutrophic species, sensitive to organic pollution)
can be useful in evaluating the type of pollution involved.
Comparison to other bioindicator organisms
taneous comparisons of some or all of these to assess
the relative usefulness of particular groups of organ-
isms - with particular emphasis on diatoms and
macroinvertebrates. In the examples below (contin-
ued from the previous section), diatom communities
showed comparable changes to macroinvertebrates in
relation to water quality, but (with the exception of
the IPS index) were generally less sensitive.
Although routine monitoring of all but the deepest
rivers has been based, for many years, on macroinver-
tebrates (e.g. De Pauw and Hawkes, 1993), a range
of other bioindicator organisms is available. These
include diatoms, other algae, fishes, aquatic and ripar-
ian macrophytes. Various authors have made simul-
Case study 3.3 Comparisons of diatom indices with other bioindices
1. Use of different bioindicators for assessing water quality in Greek Rivers. Iliopoulou-Georgudaki et al.
(2003). This study was carried out on river sites with water quality ranging from very poor to very good
and used bioindices based on diatoms (see previously) plus four other groups of organisms. Sampling of
fish and macrophyte vegetation gave only limited environmental assessment, with macrophytes in particular
being incapable of a graded response to varying degrees and kinds of stress. Macroinvertebrates and diatoms
recorded the full range of pollution conditions, but indices based on macroinvertebrates were considered to
be the most sensitive - responding more readily than diatoms to transient changes to environmental state.
2. Selected rivers in England and Scotland. Ke l ly et al. (1995a) found that their diatom indices were significantly
correlated with two benthic macroinvertebrate indices - BMWP (Biological Monitoring Working Party scores)
and ASPT (Average Score Per Taxon), both used routinely for water quality monitoring in the United
Kingdom.
3. Metal pollution in a lowland river. Comparison of macroinvertebrates and diatoms as bioindicators by De
Jonge et al. (2008) showed that diatom communities most closely reflected changes in metal concentration,
with distinct taxa being associated with low (e.g. T. flocculosa), moderate (Ni. palea) and high (Eolimna
minima) zinc levels. In contrast to diatoms, macroinvertebrate communities most closely followed physical-
chemical variables and the effects of metal pollution. The combined use of both groups for biomonitoring
was considered to be more appropriate than separate use of either.
 
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