Lakes and Watercourses
Lakes and Watercourses
Lakes and Watercourses
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APPENDIX 2<br />
Calculation of index <strong>and</strong> other<br />
parameters for assessing<br />
benthic fauna<br />
(1) Shannon-Wiener’s diversity index (Shannon, 1948) is calculated as:<br />
s<br />
n i<br />
n i<br />
H’= – Σ — log 2 —<br />
i=1 N N<br />
where N = the total number of individuals, <strong>and</strong> n i = the number of<br />
individuals of the ”i”th species.<br />
(2) The ASPT index (average score per taxon) (Armitage et al., 1983) is<br />
calculated by identifying organisms found in the sample at family (taxon)<br />
level (class for Oligochaeta). Each family is given a point score representing<br />
its tolerance to pollution (see below). The scores are added up <strong>and</strong><br />
the total divided by the total number of families recorded<br />
The following families score 10:<br />
Siphlonuridae, Heptageniidae, Leptophlebiidae, Ephemerellidae,<br />
Potamanthidae, Ephemeridae,Taeniopterygidae, Leuctridae, Capniidae,<br />
Perlodidae, Perlidae, Chloroperlidae, Aphelocheiridae, Phyrganeidae,<br />
Molannidae, Beraeidae, Odontoceridae, Leptoceridae, Goeridae,<br />
Lepidostomatidae, Brachycentridae, Sericostomatidae.<br />
The following families score 8:<br />
Astacidae, Lestidae, Agriidae, Gomphidae, Cordulegasteridae, Aeshnidae,<br />
Corduliidae, Libellulidae, Psychomyiidae, Philopotamidae.<br />
The following families score 7:<br />
Caenidae, Nemouridae, Rhyacophilidae, Polycentropodidae,<br />
Limnephilidae.<br />
The following families score 6:<br />
Neritidae, Viviparidae, Ancylidae, Hydroptilidae, Unionidae, Corophiiidae,<br />
Gammaridae, Platycnemididae, Coenagriidae.<br />
The following families score 5:<br />
Mesoveliidae, Hydrometridae, Gerridae, Nepidae, Naucoridae,<br />
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