Choice of benthic macroinvertebrate-based metrics for assessing water
quality in the littoral zone under anthropogenic disturbance in southern
Lake Kivu (Central Africa)
Abstract
Benthic macroinvertebrates are widely used to assess the ecological
quality of fresh waters. This is because they are in direct contact with
the aquatic environment and respond differently to pollutants and
changes in the watershed, which are difficult to assess by toxicological
or chemical monitoring alone. this study used benthic macroinvertebrate
parameters to assess the quality of the nearshore waters of lake Kivu.
Twenty-six metrics covering various aspects of the community were tested
using whisker plots to compare their sensitivity in discriminating
between reference and disturbed stations. Nine parameters (% EPT taxa,
% Diptera taxa, % Chironomid taxa, % Insect taxa; % no Insects taxa,
ratio EPT/Chironomid taxa, % moderate tolerant taxa, % very moderate
tolerant taxa, Family Biotic Index) were found to be sensitive and were
able to discriminate between reference and disturbed stations. All
sensitive metrics, with the exception of the percentage of EPT taxa,
were positively and/or negatively correlated with the physico-chemical
parameters affected by the changes in the littoral zone. The combined
values of the three calculated biotic indices (ASPT, BMWP and FBI)
showed that the biological water quality varies from moderate to good in
the reference stations and from average to poor in the disturbed
stations. It is concluded that metrics based on benthic
macroinvertebrates are effective for assessing water quality in the
littoral zone of Lake Kivu in the context of the lack of historical
water quality databases and specific tools for toxicological assessment.
It is suggested to compare the performance of this approach with others
currently used in bio-indication.