Ecological attributes of aquatic invertebrates in two water turbidity scenarios in a lake of the Pantanal, Brazil

Abstract

The objective of this work was to determine the taxonomic structure and Functional Feeding Groups (FFGs) of benthic invertebrates and their roles in two different water turbidity scenarios in a floodplain lake in the Pantanal wetland (Sinhá Mariana Lake, Barão de Melgaço, state of Mato Grosso). We studied the benthic invertebrate fauna at 18 sampling sites in periods of high turbidity (HT) and low turbidity (LT) during high water (HW) and low water (LW). We hypothesize that the structure of Chironomidae assemblages (species and functional feeding groups) varies between sites in Sinhá Mariana Lake, and the density and diversity attributes of species in this family and their functional feeding groups are reduced under increased turbidity. Depth, water temperature, turbidity, pH, pCO₂, water color, and organic matter content of the sediment were analyzed in each sampling site. Chironomidae presented higher density and diversity in periods of high water (HW) in sites with low turbidity water (LT). The dominance increased in periods of low water (LW). The main FFGs were represented by collector-gatherers, while the smallest groups corresponded to shredder-herbivores (50% and 9% of the total abundance, respectively). Collector-gatherers (Aedokritus sp., Chironomus strenzkei, Goeldichironomus petiolicola, G. maculatus, Beardius phytophilus), predators (Ablabesmyia gr. annulata, Labrundinia sp. and Cryptochironomus brasiliensis) and shredder-herbivores (Asheum sp., Polypedilum sp., Polypedilum gr. fallax) predominated in high water (HW) periods. A change in the community structure from the HW to LW was evidenced, characterized by the substitution of collector-gatherers for collector-filterers. Notodiaptomus deitersi (Crustacea) was dominant in LW (dominance index = 10.9) and Aedokritus sp. (Insecta) in HW (dominance index = 5.4). Water turbidity and the hydrological cycle are important factors determining spatial and temporal patterns in communities, particularly changes in FFGs. Changes in turbidity in different sites and periods alter the structure of trophic communities and lead to questions about the main drivers of communities in Pantanal wetlands as areas of high ecological relevance for maintaining biodiversity.