Vol. 9 No. (2): 65 - 82 (2018): Benthic Macro Invertebrates as Potential Indicator of Water Quality in Ajiwa Reservoir Katsina State North Western Nigeria

Benthic macro invertebrate’s ability to indicate various types of anthropogenic
stressors is widely recognized as an integral component of freshwater biomonitoring. In
case of pollution, biodiversity of the aquatic community can be affected and the species
composition changes from natural species to tolerant species. Study on the benthic
macro invertebrates as potential indicator of water quality in Ajiwa reservoir, Katsina
State was carried out from November, 2015 to October, 2016, in terms of physical and
chemical parameters and biotic indices. For this purpose, macro benthic invertebrates
and water samples were taken from five sampling location once monthly. Benthic macro
invertebrate samples were collected with the aid of Ekman grab and was transferred
into labelled plastic storage bottle and preserved with 70% ethanol prior to sorting and
identification with the aid of standard keys. Physicochemical parameter were
determined using standard methods, procedures and instruments. The results of
identification and counting of the abundance of benthic macro invertebrate was used to
determine some biotic indices (Biological Monitoring Working Party-BMWP and
Average Score Per Taxon -ASPT) and diversity indices (Margalef, Simpson and Shannon
and Weaver Diversity indices). Fifteen physicochemical parameters were determined.
Some of their mean value were; Water Temperature (27.15±2.42 ), pH, (7.85±2.01),
Free CO2 (3.47±0.78mg/L), Turbidity (98.0±2.28NTU), TDS (85.68±2.71mg/L),
Electrical Conductivity (158.55±3.04μS/cm), Total Hardness (72.16±2.37mg/L), DO
(6.10±0.13mg/L), BOD (3.41±2.31mg/L), Calcium (64.34±1.35mg/L), Total alkalinity
(96.27±3.09mg/L), COD (4.11±1.10mg/L), Magnesium (5.36±2.46mg/L), Phosphate
(1.42±0.96mg/L) and Nitrate (2.07±1.13mg/L). Thirty five (35) different taxa
belonging to twenty four (24) families from a total of 4550 individuals’ organisms were
recorded. The relative percentage composition of the major taxonomic groups to the
overall macro benthic population at the different stations revealed that the study area
was inhabited by the following order Oligochaete (40.28%), Molluscs (24.08%), Diptera
(19.29%), Odonata (5.78%), Coleoptera (3.94%), Nematodes (3.38%) and Hemiptera (3.24%). BMWP had 57 scores; indicating moderately polluted water body in station 1
and 5 with abundance of pollution tolerant taxa such Chironomidae, Lymnaeidae,
Tubificidae and Planorbidae which revealed the impact of anthropogenic activities at some sampling locations of the reservoir. It is therefore recommended that
uncontrolled discharge of agrochemicals within the vicinity of the reservoir through
irrigation and other anthropogenic activities such as cattle rearing, bush burning etc.
should be controlled in order to curtail degradation of the aquatic biota over a period of
time.