Abstract
A recent sediment core was collected from a heavily polluted irrigation pond, “Niinomi-ike”. Vertical distribution of species composition of diatom assemblages was examined to evaluate their succession in relation to phosphorus concentration in the sediments. It was found that the species composition of planktonic and periphytic assemblages in the lower part of the core was replaced by different species in accordance with the increase in total-phosphorus concentration in the sediment. Thus in the planktonic assemblages, Cyclotella comta, C. stelligera, Melosira ambigua and M. distans were replaced by C. meneghiniana, C. pseudostelligera and M. granulate. In the periphytic assemblages, Achnanthes minutissima was also replaced by Navicula frugalis and Nitzschia palea. Additionally, there is the decrease in frustules of acidophilous taxa. The succession process observed in the planktonic assemblages was characterised by the replacement of the related species in the same genus. Based on the succession of diatom assemblages, it was concluded that this pond has changed from a eutrophic one to a hypereutrophic one, and the saprobity in the periphytic environment has changed from a oligo or β-mesosaprobic status to an α-mesosaprobic one.
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Schedule a callMore From: Japanese Journal of Limnology (Rikusuigaku Zasshi)
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