Influence of Cattle Activity in Floodplains on the Zooplankton Community During a Period of Water Retraction

Freshwater ecosystems are of great importance but increasingly threatened by human land uses such as intensive livestock production. We investigated the influence of cattle grazing in floodplains on the zooplankton community during a period of water retraction. We hypothesized that cattle activity in surrounding shallow lakes acts as an environmental filter for zooplankton, with its effect depending on the hydrological conditions. Accordingly, we analyzed changes in the taxonomic and functional diversity metrics in three lakes characterized by different grazing management (no-cattle; short grazing period with high stocking rates; and long grazing period with low stocking rates) over a nine-month period into three periods of water retraction (flood, early low water, and late low water). Functional diversity indexes (FRic, FEve, FDis) were influenced by grazing management and the periods of water retraction, without interactive effects, while taxonomic indices (H’, J’, D’) did not show significant relationships with any of these variables. The FRic and FDis indices decreased in lakes subjected to cattle activity, whereas FEve and FDis increased during lower water periods. Functional and taxonomic composition exhibited different patterns among lakes according to grazing management and the periods of water retraction. Overall, a similar composition was found during the flood period but it diverged in the subsequent periods of water retraction. Besides, cattle activity reduced the functional and taxonomic composition in the late low water phase. Our findings suggest that cattle activity acts as an environmental filter for zooplankton altering the functional diversity and composition through the progress of water retraction.