An investigation on the water quality and aquatic insect community of an oxbow lake (Phulbari anua) of south Assam, NorthEast India was carried out d uring February to April, 2010.
Aquatic insect community of the oxbow lake was represented by 9 species belonging to 9 families and 4 orders during the study period.
Order Ephemeroptera and Hemiptera were found to be dominant.
Record of 5 species and 5 families from the order Hemiptera showed that this is the largest orderin terms of aquatic insect diversity of the lake.
Computation of dominance status of different species of aquatic insects of the lake based on Engelmann’s Scale revealed that Anisops lundbladiana and
Cloeon sp. were eudominant in the system.
The Shannon Weiner’s Diversity Index (H’) and Shannon evenness values (J’) were found to range from 0.30.69 and 0.53 0.97, respectively indicating
perturbation of the system.
Again in terms of physicochemical properties of water the lake is in a
satisfactory condition where all the parameters arewell within the range of IS 10500.
The DO values were found to range from 6.8 to14.8 mgl1.
Free CO2 fluctuated from 1 to 4.98 mgl1 and nitrate in water ranged from 0.4 to 2.1 mgl1.
Margalef’s water quality index values of most of the samplings also indicated clean water condition of the lake.
Correlation coefficient analyses of the environmental variables, aquatic insect diversity and density of the lake revealed that aquatic insect diversity of the lake is mainly governed by dissolved oxygen, nitrate, and free carbon dioxide.