Algae as Bioindicators - Freshwater Algae: Identification, Enumeration and Use as Bioindicators - page 117

Ta b l e 3 . 5 Organic Pollution: Most Tolerant Algal Genera and Species.

Pollution
Index No. Taxon Class Freshwater Habitat

Genus

1 Euglena Eu 5 Planktonic

2 Oscillatoria Cy 5 Planktonic or benthic

3 Chlamydomonas Ch 4 Planktonic

4 Scenedesmus Ch 4 Planktonic

5 Chlorella Ch 3 Planktonic

6 Nitzschia Ba 3 Benthic or planktonic

7 Navicula Ba 3 Benthic

8 Stigeoclonium Ch 2 Attached

9 Synedra Ba 2 Planktonic and epiphytic

species

10 Ankistrodesmus Ch 2 Planktonic

Species

1 Euglena viridis Eu 6 Ponds and shallow lakes

2 Nitzschia palea Ba 5 Lakes and rivers

3 Oscillatoria limosa Cy 4 Stagnant or standing waters

4 Scenedesmus quadricauda Ch 4 Lake phytoplankton

5 Oscillatoria tenuis Cy 4 Ponds and shallow pools

6 Stigeoclonium tenue Ch 3 Epiphyte, shallow waters

7 Synedra ulna Ba 3 Lake phytoplankton

8 Ankistrodesmus falcatus Ch 3 Lake phytoplankton

9 Pandorina morum Ch 3 Lake phytoplankton

10 Oscillatoria chlorina Cy 2 Stagnant or standing waters

Source : Palmer, 1969. Reproduced with permission of John Wiley and Sons Ltd.
Ten most tolerant algal genera and species listed in order of decreasing tolerance. Algal phyla -
Cyanophyta (Cy), Chlorophyta (Ch), Euglenophyta (Eu) and Bacillariophyta (Ba). Pollution index -
see text.

the average of all recorded species within the genus,
and is perhaps less useful than the species rating -
where single, readily identifiable taxa can be directly
related to pollution level.
The species organic pollution index developed by
Palmer uses the top 20 algae in the species list (top
10 shown in Table 3.5). Algal species are rated on a
scale 1 to 5 (intolerant to tolerant) and the index is
simply calculated by summing up the scores of all
relevant taxa present within the sample. In analysing
the water sample, all of the 20 species are recorded,
and an alga is considered to be 'present' if there are
50 or more individuals per litre.
Examples of environmental scores are given
in Table 3.6, with values of

high organic pollution and 10 signifying lack of

nutrient enrichment. Palmer's index was used by
Cattaneo et al . (1995) in their studies on a fluvial
lake of the St. Laurence River system (Canada),
with values from 15 to 24 at different sampling
sites indicating moderate to high levels of organic
pollution. Care should be taken in applying this
index, since many sites with high organic pollution
(e.g. soluble sewage organics) also have high
inorganic nutrients (phosphates, nitrates), and algae
characteristic of such sites are typically tolerant to
both.
In addition to the general application of Palmer's
index using a wide range of algal groups, the index
may also be more specifically applied to benthic

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