Study of Nestedness Index using Diatoms from selected fresh water bodies of Goa

Abstract

Nestedness has been recognized as a characteristic pattern of community organization. Present study was carried out by selecting four fresh water bodies from the state of Goa, to understand whether freshwater diatom communities exhibit nested structure; to know the possible drivers of species nestedness and also to find out the habitat showing best nested pattern. Physicochemical parameters of water bodies like turbidity, temperature, total chlorophyll, BOD, nitrates and phosphates were analyzed. The presence - absence matrices for diatoms were built using nestedness software The study revealed that Syngenta, Lotus and Curtorim Lakes, are most hospitable sites while Khandola Pond having idiosyncratic species lies at the bottom position in supporting the growth of diatoms. Pinnularia graciloids, P. gibba, Navicula halophila, N. mutica, N. radiosa, N. rhynococephala and Synedra ulna, had common niche requirements. Selected water bodies were organically as well as anthropogenically polluted. Presence of Navicula halophila and N. mutica indicated organic pollution in all four water bodies. Presence of Synedra ulna indicated anthropogenic pollution in Syngenta, Lotus and Curtorim lakes while N. rhynococephala indicated anthropogenic pollution in Khandola Pond. Idiosyncratic species like Gomphonema subtiles, G. parabolum, Pinnularia graciloids, Eunotia tumida, Melosira islandica and Navicula microcephala were also observed in the study sites. Physico- chemical parameters tested during study proved to be the possible drivers of nestedness. Principal component analysis identified total chlorophyll, BOD, turbidity, temperature, nitrates, and phosphates as the key factors that controlled structure of diatom communities In all 21species of diatoms belonging to 12 genera were recorded during 24 month study. The matrix fill was 79% at Syngenta Lake, 66.6% at Khandola Pond, 78.7% at Lotus Lake and 71.2% at Curtorim Lake with respective system temperatures of 12.730, 2.120, 4.730and 12.860. Analysis revealed that the diatom assemblages of selected water bodies are highly nested.