Diversity and Distribution of Benthic Macro Invertebrates in Ayiroor River, Kerala, South India

Macro benthic invertebrates fauna of Ayiroor River at Kerala, South India was conducted from February 2013 to January 2015. Ayiroor River is the smallest river in Southern Kerala lies between 8.75N latitude and 76.71E longitude and drains an area of 66 Sqr. Km. Sediment samples were collected from three different stations along the river. A total of 312 individuals representing 4 taxa (insecta, oligocheates, bivalves and gastropods) and three phyla (Arthropoda, Mollusca and Annelida) were collected from the three stations of the river during the study period. Of these Arthropoda contributed the largest share constituting 70 % of the total macro-benthic invertebrate fauna, followed by Mollusca, 22 % and Annelids 8 %. The textural analysis of the sediment showed that sand was the predominant fraction in all the stations followed by silt and clay. The presence of Chironomus larvae and Tubifex tubifex indicate the effect of pollution from anthropogenic sources, but not too much extent because of their low number in the study area. The water quality of the Ayiroor River was deteriorated by sewage effluents and agricultural activities, diminishing the abundance of benthic macro-invertebrates.