Seasonal variation of macroinvertebrate density and impact of anthropogenic activities in an Ephemeral stream, Baghjan in the Lakhimpur district of Assam

Abstract

This study is based on assessment of different factors affecting distribution of certain macro invertebrate species as well as health of one forested ephemeral stream, Baghjan situated in the Lakhimpur district of Assam. A total of 23 macro invertebrate species belonging to 13 families, 5 orders of class Insecta of phylum Arthropoda have been recorded from the stream with monthly fluctuation. Post monsoon showed comparatively more numbers of macro invertebrates than monsoon. Effects of different physicochemical parameters are also considered. Estimation of different physico-chemical parameters such as dissolved oxygen, free carbondioxide,total acidity,total alkalinity,chloride,pH,conductivity was done.Correlation was performed among  macroinvertebrate density and physicochemical parameters. Dissolved oxygen, total alkalinity,pH were found to be positively correlated with macro invertebrate density, but free carbondioxide,total acidity,conductivity,stream depth and stream width were found to be negatively correlated with macro invertebrate density. Different anthropogenic activities are considered to have significant effect on the macro invertebrate assemblage. The main anthropogenic disturbances in the studied stream such as sand and gravel mining, illegal felling of trees, live stock grazing, construction of rail road, open defecation, laundry activities, disposal of domestic waste materials etc. in the studied stream were recorded.