TITLE:
Impact of Dewatering on the Spatio-Temporal Distribution of Benthic Macroinvertebrate Communities in the Okpara River, Benin
AUTHORS:
Sylvain Tayéwo Biaou, Fadéby Modeste Gouissi, Armelle Sabine Yélignan Hounkpatin, Zoulkanerou Orou Piami, Wakili Bolatito Yessoufou, Souradjou Orou Goura, Nonvignon Martial Fassinou
KEYWORDS:
Dewatering, Benthic Macroinvertebrates, Impact, Physico-Chemical Parameters, Okpara Rivers, Nord-Benin
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.12 No.2,
February
7,
2024
ABSTRACT: Surface watercourses are areas of very high ecological and heritage value.
Macroinvertebrates are bioindicators of the health of aquatic ecosystems. The aim of this study was to assess the effects of dewatering
and re-watering cycles on benthic macroinvertebrate (BMI) communities. Two
data collections were carried out at two stations
(Okpara 1 and Okpara 2) on the Okpara river before and after dewatering. Thus, 8
samples of benthic macroinvertebrates and
12 physico-chemical parameters (T°C, pH, Transparency, Depth, Conductivity, Dissolved Oxygen that were measured in situ, and BOD5,
COD, NH4+, NO3-, NO2- and PO43-) were assayed in the laboratory. Canonical Correspondence
Analysis (CCA) was used to match physico-chemical data to MIB families. Shannon
and Piélou diversity indices were used to determine the effects of dewatering on
MIBs. The increase in temperature values of pH, BOD5, COD, NH4+, NO3-, NO2- and PO43-, after re-watering indicates the effect of dewatering
on the quality of Okpara aquatic ecosystems. The benthic macrofauna collected consisted
of 62.42% insects, 0.65% crustaceans, 6.48% molluscs, 0.72% worms and 0.14% arachnids.
Whereas after re-watering, 21.67% insects, 0% crustaceans, 0.22% molluscs, 7.56%
worms and 0.29% arachnids were recorded. Insects, crustaceans and molluscs were
more abundant before dewatering than after. This was revealed by low abundances
and taxonomic richness, as well as low Shannon index values of samples collected
after re-watering.