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1. Under increasing nutrient loading, shallow lakes may shift from a state of clear water dominated by submerged macrophytes to a turbid state dominated by phytoplankton or a shaded state dominated by floating macrophytes. How such regime shifts mediate the relationship between taxonomic and functional diversities (FD) and lake multifunctionality is poorly understood.2. We employed a detailed database describing a shallow lake over a 12-year period during which the lake has displayed all the three states (clear, turbid and shaded) to investigate how species richness, FD of fish and zooplankton, ecosystem multifunctionality and five individual ecosystem functions (nitrogen and phosphorus concentrations, standing fish biomass, algae production and light availability) differ among states. We also evaluated how the relationship between biodiversity (species richness and FD) and multifunctionality is affected by regime shifts.3. We showed that species richness and the FD of fish and zooplankton were highest during the clear state. The clear state also maintained the highest values of multifunctionality as well as standing fish biomass production, algae biomass and light availability, whereas the turbid and shaded states had higher nutrient concentrations. Functional diversity was the best predictor of multifunctionality. The relationship between FD and multifunctionality was strongly positive

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Zooplankton body size is fundamentally affecting productivity, ecosystem respiration, nutrient cycling, and energy transfer and may be controlled by food availability but also water physical and chemical characteristics. However, the differences in control of water physical and chemical characteristics and food availability on zooplankton body size have rarely been investigated in subtropical systems. We tested the hypotheses that: (i) the type of environment, food availability, and water physical and chemical characteristics would influence body size distribution in the Upper Paraná River floodplain and nearby subsystems and (ii) in environments with higher food availability, small‐sized organisms would predominate showing higher abundance, whereas the opposite would occur in environments with lower food availability. To test these hypotheses, we performed partial redundancy and redundancy analyses (RDA). Our results showed that food availability, Secchi depth, and suspended inorganic matter influenced the body size structure of rotifers and cladocerans. Additionally, we observed that greater food availability was related to greater abundance of organisms, which were dominated by small‐sized zooplankton (size classes C2 and C1 in rotifers, and class C2′ in cladocerans). It was possible to associate different zooplankton body size spectra with phytoplankton biovolume and planktonic ciliate abundance. We suggest that large‐bodied cladocerans could have a competitive advantage over rotifers and small‐sized cladocerans when resources are scarce, because the large‐sized group could explore a wider range of resource types.

Anthropogenic translocations are the main vectors of intercontinental invasions. Molecular tools have been important in the study of biological invasions, helping to identify the source of non‐native species mainly when these species are rapidly colonizing the new territories. The aims of this study were: (i) to characterize genetic sequences of the Daphnia lumholtzi population in Brazil (Upper Paraná River floodplain) for the first time; (ii) to compare these sequences with available sequences at GenBank; and (iii) to contribute new sequences of gene 12S from D. lumholtzi. Specimens were collected from a lake of the Paraná River for gene comparison (COI and 12S sequences). Genetic sequences from populations outside Brazil were obtained from GenBank. D. lumholtzi specimens sequenced in this study are genetically close to populations from the United States and Mexico and considerably distant from Australian populations. Our data confirm that populations present in the Paraná River floodplain probably came from the United States, where they arrived through introduction of African fish. The genetic similarity between our specimens and populations from Mexico and the morphological discrepancy between them reinforces the importance of molecular analysis for accurate identification of a species and its origin.

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Studies considering the functional traits of organisms, populations, and communities functional indices increase the understanding of many factors on ecosystem functioning. Here, we analyze the predation effect (by fi sh) on zooplankton functional diversity and the effects of biomass and density of periphytic algae on zooplankton feeding type trait and body size. We expect that intense predation by fi sh on zooplankton leads to higher values of zooplankton functional diversity and that food resource will be positively related to the abundance of zooplankton trait and body size.For that, microcosms were established (T1-fi sh-absence, and T2-fi sh-presence, both with periphytic algae as food). We observed that fi sh presence decreased zooplankton functional diversity through modifi cations in the availability of nutrients and algae, through the middle-out effect. We also observed that body size had a negative relationship with the food resource, reaffi rming that high food availability in subtropical lakes is linked to small-bodied zooplankton. The raptorial copepods covariate positively with the periphytic algae, which was an alternative food resource and, in this case, the main form of carbon input into the system. In this study, omnivorous fi sh reduced zooplankton functional traits, which can alter the energy stock and energy fl ow in aquatic ecosystems.

Testudinella is a taxon of Rotifera broadly distributed in Brazil. In a recent collection in marginal lakes connected to the Paranapanema River (São Paulo, Brazil), we found specimens of Testudinella mucronata and T. patina with concavities on their lorica. The objective of this study was to describe the concavities observed in individuals of both species and discuss their possible causes. Plankton samples were collected at two sampling stations, in the pelagic (PZ) and littoral (LZ) zones of the Panema and Coqueiral lakes; both of these lakes are ultra-oligotrophic and not polluted. For T. mucronata, 4% of individuals with concavities were found in the PZ of Coqueiral lake and 50% in the LZ of Panema lake. In T. patina, the proportion of specimens with concavities corresponded to 34% in the LZ of Panema lake and 17% in PZ of Coqueiral lake. In this study, we discussed that low water temperatures, predation events and/or recent hatching are factors that may justify the concavities in the lorica of specimens of our work.