Dynamics of zooplankton community (except protozoa) in the Parque Norte lake, Medellín (Antioquia, Colombia)

Abstract

With the purpose to evaluate the structure, density, and temporal variation of the zooplankton community of the lake Parque Norte, Medellín (Antioquia, Colombia), and also, to study the climatic, physical, chemical, and biological variables associated with it, zooplankton organisms were sampled weekly in one station in the center of the lake from May 1999 and to February 2000. Environmental variables were measured monthly. The zooplankton community was composed mainly by three species, the calanoid copepod Arctodiaptomus dorsalis, the rotifer Brachionus plicatilis, and the cladoceran branchiopod Moina macrophtalma. During most of the studied period, the community was numerically dominated by A. dorsalis. Dominance values were low while eveness values were high, probably due to the codominance of morphotypes of A. dorsalis. Temporal variation of the numerical structure of the community showed low variability explained by the low variability of the richness, eveness, and dominance coeficients. Temporal dynamics of the different stages of the community indicated by the coeficient of variation, was high. While temporary coeficient of variation of both size classes of M. macrophtlama, copepodites I to V and ovigerous females of B. plicatilis were the highest; males, not ovigerous females of A. dorsalis, and not ovigerous females of B. plicatilis showed the lowest changes during the sampling period. This last phenomen can be explained by a high association among the organisms of the community that is due to the low competition among them because they occupied different ecological niches. Variation in density of zooplankton community depends on the rise of the population of Botryococcus braunii, the dominant algae.