Impact of different land uses and covers on taxonomic and functional diversity and secondary production of benthic fauna in tropical reservoirs

Abstract

Land use and land cover (LULC) directly and indirectly affect the diversity, productivity, and structural dynamics of benthic fauna in aquatic ecosystems. The mechanisms of these effects, particularly in artificial reservoir systems, remain elusive. This study employed explanatory modeling to investigate the pathways through which LULC affects the physicochemical properties of water, the taxonomic and functional diversity, and the secondary production of macroinvertebrates benthic in reservoirs. We analyzed six reservoirs characterized by severe drought conditions in the Brazilian semiarid from 2014 to 2019. Exposed soil, open vegetation, and human occupation in the riparian zones of the reservoirs were the LULC classes with the most significant impact on total dissolved solids, dissolved inorganic nitrogen, salinity, and water volume. In contrast, an increase in forested areas was associated with a reduction in total phosphorus levels in the water. These human activities negatively affected taxonomic diversity while positively influencing secondary production by increasing the biomass of generalist and tolerant organisms. The negative relationship between forested areas and taxonomic diversity may be attributed to the extreme reduction in water volume caused by drought and the combined effects of multiple land uses surrounding the reservoirs. This exacerbated environmental stress and diminished the potential benefits of riparian vegetation on biodiversity. These findings highlight the importance of considering multiple factors related to land use, human activities, and climate to effectively conserve water quality and biodiversity in the reservoirs.