Abstract

VELASQUEZ-DUQUE, Yesica; VILLABONA-GONZALEZ, Silvia Lucía  and  PALACIO-BETANCUR, Hilda. Influence of logjams in the structure of zooplankton in a tropical dam. Rev. acad. colomb. cienc. exact. fis. nat. [online]. 2021, vol.45, n.174, pp.217-228.  Epub Sep 18, 2021. ISSN 0370-3908.  https://doi.org/10.18257/raccefyn.1269.

Log jams are accumulations of wood in riverbeds and floodplains of rivers with variable sizes whose composition depends on the characteristics of the riparian forest. We evaluated the influence of a log jam formed in the riverine zone of the Amaní reservoir on the spatial and temporal structure of the zooplankton during the dry and rainy seasons in 2016 and its relationship with the phytoplankton and the physical and chemical conditions. We took samples of plankton and physical and chemical variables in sites located before, in the beginning, the middle, the end, and after the log jam. A total of 64 taxa of the three major groups of zooplankton were recorded (rotifers, cladocerans, and copepods). The spatial and temporal differences in zooplankton densities were significant and related to the transparency and availability of some nutrients. The highest values of the zooplankton diversity were found in the middle, at the end, and after the log jam probably because it increased habitat heterogeneity, food availability, and refuge. The community presented temporary changes in the dominance of taxa possibly as a result of water level fluctuations in the reservoir level during the three seasons analyzed. The best conditions for zooplankton development were found in the middle, in the end, and after the log jam probably because it decreased the disturbance pressures and increased heterogeneity, food availability, and refuge. The community presented temporal changes in the dominance of taxa possibly as a result of water level fluctuations in the reservoir.

Keywords : Log jam; Alfa diversity; Beta diversity; Rotifers; Microcrustaceans; Reservoir.

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