Composition, species richness and patterns of nycthemeral vertical distribution of planktonic cladocereans in a black water Amazonian lake

The aim of this study was to identify patterns of vertical distribution of planktonic cladocerean populations throughout the diel cycle, during the low and high water periods, and its ecological implications for a black water Amazonian lake. Tupé Lake is a black water lake located near the Brazilian city of Manaus. A channel links the lake with the Negro River and its flood pulse. This study was performed in a low-water period (November 2005) and in a high-water period (June 2006). Samples were taken on a 24-hour cycle, every 4 hours and at each meter of the water column, using a Schindler-Patalas trap equipped with a 55µm size mesh. A total of 16 species were registered during the low water period, wherein Bosminopsis deitersi, Moina minuta, and Ceriodaphnia cornuta were the most abundant species. B. deitersi migrated to the bottom during the afternoon, while M. minuta, Moina reticulata, and Holopedium amazonicum remained at the bottom for the entire diel cycle. During the high-water period, a total of 18 species were observed, and B. deitersi, C. cornuta, and Diaphanosoma polyspina were the most abundant species. During both sampling periods, no pattern was detected for C. cornuta. Generally, vertical patterns of distribution were less evident in the high water period, due to the mixing of the lake