Assembleia de macroinvertebrados aquáticos em um ambiente lêntico cárstico tropical

Abstract

Knowledge about aquatic macroinvertebrates in lentic karst environments is still scarce, especially in the Neotropical region. Lagoa Misteriosa is one of these environments, presenting a unique characteristic for karstic lakes: two distinct annual periods, With Algal Bloom - CFA (low transparency) and Without Algal Bloom - SFA (high transparency). Thus, this study aimed to characterize the aquatic macroinvertebrate assemblage associated with macrophytes in the karstic doline Lagoa Misteriosa. Additionally, we investigated whether the periods influence the structure of aquatic macroinvertebrate assemblages. Sampling was carried out bimonthly from October 2021 to August 2022 (three samples in each period). The collected macrophytes were washed under running water to obtain aquatic macroinvertebrates, and the analyses were conducted using R software. A total of 9834 individuals were sampled, distributed across 42 taxa. Among these, mollusks represented about 51% of the individuals, with Hydrobiidae being the densest and the presence of an exotic mollusc species: Melanoides tuberculatus. Aquatic insects accounted for 29 taxa and seven orders, with the order Coleoptera being the most abundant, especially the Elmidae family. Regarding the CFA and SFA periods, there was a significant difference in the composition and density of aquatic macroinvertebrates, with 5,831 individuals sampled during the CFA period (59%), 39 taxa, a higher density of Microcylloepus. Meanwhile, 4003 individuals (41%) and 27 taxa were sampled during the SFA period, dominated by Hydrobiidae molluscs. Redundancy analysis demonstrated that dissolved oxygen and taxa Chironominae, Polycentropus, and Microcylloepus positively correlated with the CFA period, whereas TDS parameters, transparency, and Hydrobiidae taxa negatively correlated with the SFA period. We infer that low water transparency and increased sunlight might be affecting macrophyte density and consequently the structure of aquatic macroinvertebrate assemblages. With this study, we contribute to filling existing knowledge gaps about organisms present in tropical freshwater lentic karst ecosystems, which may be used for future conservation and protection procedures for these aquatic ecosystems.