Unravelling the influence of cattle stocking rate on the macroinvertebrate community of freshwater wetlands subjected to hydrological modifications in three hydroclimatic periods

BERÓN, MARÍA CECILIA; MONTALTO, LUCIANA; AQUINO, DIEGO SEBASTIÁN; QUINTANA, RUBÉN D.; FLORES, MARINA; LABAS, MARISOL; MESA, LETICIA

ENVIRONMENTAL RESEARCH

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2024 vol. 251

0013-9351

The Paran´a River Delta in South America, a large wetlands macromosaic, faces threats from climate change,human activities like livestock intensification, and hydrological modifications driven by the construction ofwater management infrastructure to prevent flooding in productive lands. Macroinvertebrates, essential forwetland health, are affected by cattle-induced changes in water quality, nutrient enrichment, and trampling,posing challenges to the ecosystem’s ecological balance and long-term survival of these organisms. In this study,we analyzed the impact of two categories of cattle stocking rates (low and high) on the taxonomic and functionalstructure of the aquatic macroinvertebrate community in freshwater marshes. In addition, we compare the influenceof cattle stocking rate on macroinvertebrates in natural and modified freshwater marshes, and, finally,the effect of cattle stocking rate in three contrasting hydrometeorological periods: a drier, a humid, and anextreme drought period. Samplings were conducted in 16 freshwater habitats of the Lower Paran´a River Delta,examining variables such as temperature, pH, dissolved oxygen, coliforms, and nutrient concentrations. Macroinvertebrateswere collected and functional and taxonomic metrics were estimated. Statistical analyses,including ANOVA and Kruskal-Wallis tests, were conducted to evaluate the effects of cattle stocking rates, hydrologicalmodifications, and hydrometeorological periods on macroinvertebrate metrics and environmentalvariables. RDA, PERMANOVA, and SIMPER analyses explored the relationships between assemblage compositionand environmental factors. High stocking rate altered the community structure, modifying its composition anddecreasing the density, taxonomic and functional richness. Moreover, hydrological alterations exacerbated thesenegative impacts of cattle overstocking in macroinvertebrates. Under severe drought conditions, only tolerantspecies can survive cattle overstocking conditions. Our findings provide relevant insight into the ecological risksassociated with cattle overstocking in natural and modified freshwater marshes and underscore the need tocontrol cattle stocking rates in extreme drought to avoid loss of ecological functions.