Y. Cao et al., ANALYZING BENTHIC MACROINVERTEBRATE COMMUNITY CHANGES ALONG A POLLUTION GRADIENT - A FRAMEWORK FOR THE DEVELOPMENT OF BIOTIC INDEXES, Water research, 31(4), 1997, pp. 884-892
The present study used a new model to analyse macroinvertebrate commun
ity changes along an organic pollution gradient in the River Trent sys
tem, U.K. The model divides community changes into four types, three o
f which are further differentiated into two sub-types. These type and
sub-type variations are of different ecological significance. The resu
lts showed that as water quality deteriorated, species loss, the avera
ge abundance of sample-specific species and the average maximum ratio
of in-common species abundance increased substantially, while the numb
ers of persisting species were reduced rapidly. However, polluted site
s were also found to gain some tolerant species, particularly at sligh
tly polluted sites. The abilities of several commonly used biotic indi
ces to summarise these changes were compared. The design of the Chandl
er score system appeared to be more effective than the other systems e
xamined. The Chandler-ASPT was modified by multiplying by log S (speci
es richness/the number of key taxa) to improve its sensitivity over th
e lower range of water quality while retaining its effectiveness over
the upper range of water quality. The modified index was tested using
a published data set. (C) 1997 Elsevier Science Ltd.