Historical Zooplankton Composition Indicates Eutrophication Stages in a Neotropical Aquatic System: The Case of Lake Amatitlan, Central America

This paper presents a study of freshwater zooplankton biodiversity, deemed as a reliable indicator of water quality. The Guatemalan Lake Amatitlan, currently used as a water source, has shown signs of progressive eutrophication, with perceptible variations of the local zooplankton diversity. Biotic and abiotic parameters were determined at four sites of Lake Amatitlan (Este Centro, Oeste Centro, Bahia Playa de Oro, and Michatoya) in 2016 and 2017. The local composition, the species richness and abundance of zooplankton, and the system environmental parameters were analyzed during both years surveyed. Biological data suggesting eutrophication of this tropical system were obtained, including a high rotifer abundance (11 species: the rotifers Brachionus havanaensis (109 ind L-1) and Keratella americana (304 ind L-1) were the most abundant species in this lake). The presumably endemic diaptomid copepod species, Mastigodiaptomus amatitlanensis, was absent in our samples, but we report the unprecedented occurrence of two Asian cyclopoid copepods (i.e., Thermocyclops crassus and Mesocyclops thermocyclopoides) for Lake Amatitlan and Guatemala. The presence of larger zooplankters like adults and immature copepods (i.e., Arctodiaptomus dorsalis) and cladocerans (Ceriodaphnia sp.) at site "Este Centro" indicates a relatively healthy zooplankton community and represents a focal point for managing the conservation of this lake.