Effect of organic and inorganic turbidity on the zooplankton community structure of a shallow waterbody in central Mexico (Lake Xochimilco, Mexico)

Abstract

Aim: Lake Xochimilco is shallow (< 2m) water-body in Mexico City consisting of several interconnected canals. It is now eutrophic, with high levels of turbidity as a result of suspended sediment and phytoplankton blooms. We selected two sites, the Rowing channel with organicturbidity due to cyanobacterial blooms and the Main channel with inorganic turbidity from re-suspended clay. The aim of this work was to present data on zooplankton dynamics in two channels of the lake overone year (June, 2013 to May, 2014). Methodology: We collected zooplankton by filtering 80L of water from two sites in each of the canals, as well as measuring temperature, pH, conductivity, dissolved oxygen, nitrate-N and phosphate-Ps, Chlorophyll-a, and Secchi disk transparency at each of the sites. Results: The zooplankton community was dominated by rotifers; cladocerans and copepods were few. The common rotifer genera in thelake were Keratella, Brachionus, Polyarthra, Trichocerca, Filinia, Asplanchna chydorid cladocerans like Chydorus sphaericus, Pleuroxus varidentatus, Alona sp. and copepods Acantho cyclops americanus and Microcyclops rubellus. The canonical correspondence analysis (CCA) in the Rowing channel station, showed that the first two ordination axes explained 46% of the variance of the species data in CCA. The first and second axes were well correlated with the environmental data. The Monte Carlo permutation test was significant on the firstaxis. Interpretation: Our study showed that the presence of organic turbidity as observed in the rowing channel had a greater adverse effect than the inorganic turbidity on zooplankton density and diversity.