Vol. 9 No. (2): 166 - 179 (2018): Diversity and Community structure of Macroinvertebrates in Anthropogenically stressed water body in Delta state, Nigeria.

The macroinvertebrate community of Agbara- Otor River system at Agbara-Otor,
Omavovwe and Afiesere in Delta state were studied, to evaluate the ecological impact of
dredging on their community structure from March to May, 2017. Kick sampling
method was adopted for macroinvertebrate sample collection. Two litres of water
sample was also collected for the evaluation of the environmental variables. The range
of results for air temperature(31.0-37.5°C), water temperature(27.3-32.3°C),
transparency (0.03-0.81m), total solids (0.35-0.7mg/L), conductivity (27.03-51.6
µm/Scm), pH (7.8-9.7), alkalinity(13.0-33.3mg/CaCO3), acidity (25.0-72.5), dissolved
oxygen (3.1-5.7mg/L), biochemical oxygen demand (1.53-5.7mg/L), nitrates (0.005-
0.006mg/L) and phosphates (1.13-1.67mg/L) were obtained. A general low taxa (7)
comprising of 403 individuals with15 families were recorded. Coleoptera (41.2%) was
the dominant family, followed by Odonata (16.1%), Ephemeroptera (10.7%),
Hemiptera (10.4%), Trichoptera (9.93%), Decapoda (8.68%) and the least, Diptera
(2.98%). The highest diversity indices range for Shannon-weiner of 1.6-1.7 was
obtained indicating very poor water quality and unstable system. The first axes of the
three principal components in all stations extracted over 90% of the macro
invertebrates- environmental variables influence implicating nutrients, organic load
and sediments. Therefore, this study identified dredging as a serious threat to this water
quality and its macroinvertebrates. Targeted ways of dredging must be adapted to
reduce ecological impacts and allow for re-establishment and protection of
macroinvertebrates and improved water quality.