Planktonic community in sequential fishponds

Abstract

In this study, the effect of the sequentially distributed fishponds in the composition of planktonic community was investigated. Samplings were performed at the water inlet of six fishponds in two periods of the year: rainy and dry seasons. Chlorophyta algae were the most abundant in the phytoplanktonic community, followed by Chrysophyta, Cyanobacteria, Euglenophyta and Cryptophyta/Dinophyta. Concerning the zooplankton, 58 and 48 taxons were registered, during the dry and rainy periods, respectively. Rotifers displayed the greatest number of taxons and was followed by cladocerans and copepods. In the rainy period, zooplankton abundance was greater in fishponds 3 and 4, in which 1,241 and 2,291 ind./L were found, respectively. During the dry period, fishponds 5 and 6 displayed greater number of organisms, with 2,574 and 3,486 ind./L, respectively. The most abundant rotifers in the rainy period were Bdelloida and Conochilus sp., followed by the cladocerans Bosmina hagmanni and Diaphanosoma birgei and by the copepod Thermocyclops decipiens. Moreover, among rotifers and copepods, Polyarthra sp., Trichocerca bidens and Argyrodiaptomus furcatus were distinctive in the dry period. A significant difference (P < 0.05) was observed between the total number of zooplanktonic individuals registered in the rainy period and that occurred in the dry one.