Qualitative habitat evaluation index and some selected macroinvertebrate taxa metrics as a diagnostic tool for assessing pollution loads in a municipal river in north central Nigeria
Pollution load in a municipal river in north central Nigeria was assessed using qualitative habitat evaluation index and some selected macroinvertebrate taxa metrics. The study was conducted for a period of twelve (12) months, spanning from March, 2017 to February, 2018, in four sampling stations. Station 1 was the reference site located in a relatively unperturbed area close to the river source. Macroinvertebrates were sampled using the kick sampling method of a D-frame net. Percentages of Ephemeroptera, Plecoptera and Trichoptera (EPT) and Chironomidae+Oligochaeta were calculated to ascertain the ecological state of the river. The Qualitative Habitat Evaluation Index (QHEI) values portray a moderately impaired site. Station 1 QHEI was 76.15% which was the highest value recorded while station 4 was the worst hit among the sampled stations with 42.69%. Percentage EPT calculated showed that station 1 had the highest composition of the group with 13.12% while station 4 % EPT was 0.147. Further lending credence to the heavily perturbed state of station 4 is the percentage Chironomidae + Oligochaeta with 7.34% composition, which is much lower than that of station 1 the relatively unperturbed station. The study was able to elucidate the level of pollution loads in each of the stations sampled and it was noticed that pollution load was increased downstream from station 1 to station 4. A more detailed study on the use of biotic indices to assess the ecological status of rivers in the North central region of Nigeria were the River Chanchaga is located is recommended to further ascertain the level of disturbance the rivers are undergoing. This can be best done using macroinvertebrates predictive protocols and traits based monitoring approach.
Keywords: Ecological Integrity, Pollution loads, QHEI, EPT, River Chanchaga, Nigeria