Abstract: Aim The construction of reservoirs in the Brazilian semiarid region is a predominant practice aimed mainly at water supply. Introducing fish in these ecosystems has generated environmental and social consequences. We analyzed articles on the ichthyofauna found in reservoirs from this region over the past 50 years. Methods This qualitative-quantitative scientometric analysis considered the scientific impact of the articles, the origin of the species studied, the main topics covered, and women´s participation in the authorship. The articles were collected from the leading research databases: Google Scholar, SciELO (Scientific Electronic Library Online), and Web of Science. Results We found 60 scientific papers on the subject. Most had low impact and visibility, and the state that contributed the most was Rio Grande do Norte (RN). The three most studied reservoirs made up almost half of the articles found (28). Research has only advanced considerably in the last decade, and the most discussed topics are related to the cultivation of commercial fish species, emphasizing pisciculture, reproductive biology, and fish nutrition. Conclusions Despite the significant number of women participating, their visibility in the scientific community remains limited, which affects the community as a whole. Besides, it is crucial to continue promoting research on fish taxonomy, phylogenetics, and functional ecology in the reservoirs of the Brazilian semiarid region.

Abstract: Aim In this study, we present the results of a project which used Landsat Collection 2 Surface Reflectance data and European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) data to develop a machine learning model to estimate Secchi depth in Lake Yojoa, Honduras. Methods Satellite remote sensing data obtained within a 7-day window of an in situ measurement were matched with in situ Secchi depth measurements and were partitioned into train-test-validate data sets for model development. Results The machine learning model had good (R2= 0.57) agreement and reasonable uncertainty (MAE = 0.58 m) between remotely estimated and in situ observed Secchi depth. Application of the machine learning model increased the monitoring record of Lake Yojoa from 6 years of measured data to a 23-year record. Conclusions This model demonstrates the utility of coordinating in situ sampling schedules of short-term research projects with satellite imagery acquisition schedules in order to increase the temporal coverage of remote sensing derived estimates of water quality in understudied lakes.

Abstract: Aim To understand the distribution of functional feeding groups (FFGs) of aquatic and semiaquatic insects associated with macrophytes in a lentic system, we tested whether the abundance of FFGs varied across sampling periods and analyzed the variation of environmental variables related to FFG composition. Methods We evaluated the distribution of FFGs in four samplings conducted in March, May, July, and September of 2022, during different seasons of the year. The sampling locations were three sites in the Ponte Lake, located in the Porto Alegre Botanical Garden, southern Brazil. Relative abundances (%) were calculated for each family and for each FFG per sampling period. In this study, each seasonal sampling was considered a sample, and the three lake points were treated as subsamples. Data analysis was performed using Principal Component Analysis (PCA), Permutational Multivariate Analysis of Variance, and the Chi-square test (χ2). Results The two-axis PCA explained 90.47% of the variation. The variables that most contributed to the formation of the first axis were temperature, pH, and dissolved oxygen, with a positive relationship, while turbidity contributed most to the second axis, with a negative relationship. The χ2 test confirmed differences in FFG abundances among the sampling periods. We collected 4.872 specimens, representing 24 families distributed across five orders. Collector-gatherers were the most abundant in the study (N = 3.126), with higher abundance in autumn (N = 899), followed by predators (N = 1.385), more abundant in summer (N = 582), and collector-filterers (N = 359), also more abundant in summer (N = 158). Conclusions These findings contribute to a better understanding of how environmental factors drive the diversity of functional feeding groups in lentic systems and highlight the ecological role of macrophytes as complex mesohabitats that are essential for the structuring of aquatic insect communities.

Abstract Aim Beta diversity is expected to increase due to environmental heterogeneity and spatial extent. However, it remains unknown whether the response of beta diversity to these variables is consistent among different taxonomic groups. I investigated whether the beta diversity of lacustrine phytoplankton, zooplankton, and macroinvertebrate communities within nine ecoregions in the United States of America correlates with environmental heterogeneity and spatial extent. Methods I used simple linear regression analyses to examine how the beta diversity of different communities was related to environmental heterogeneity and spatial extent. Results Phytoplankton and macroinvertebrate community's beta diversity was positively related to environmental heterogeneity, while zooplankton and macroinvertebrates' beta diversity was significantly related to the spatial extent (within ecoregions). Conclusions My results align with theoretical expectations that beta diversity increases due to environmental heterogeneity and spatial extent. These results contribute to a better understanding of processes structuring the composition of different aquatic communities in the United States.

Abstract: Aim This study aimed to analyze the influence of small cities on the diversity of the zooplankton community along the Almada River, Bahia. Methods The samples were collected at points upstream (Clean Waters - CW) and downstream (Active Decomposition - DA) of the urban area of three cities: Almadina, Coaraci and Itajuípe, between the years 2020 and 2023. Results Among the physical and chemical variables, only dissolved oxygen and water temperature varied significantly between CW and DA. 90 taxa were identified, of which: 60 from Rotifera, 17 from Cladocera and 13 from Copepoda. It was possible to verify the presence of dominant taxa, characteristic of eutrophic environments, in points downstream of urban areas, namely: Lecane bulla bulla, Bdelloidea, Testudinella patina and Platyias quadricornis. The community attributes with significant variation between CW and DA were: abundance, evenness and the Shannon diversity index. The Jaccard dissimilarity between the CW and DA zones was high, indicating a low rate of species sharing between the CW and DA zones. In the BIOENV analysis, the variables of dissolved oxygen and electrical conductivity associated with variation in community structure were chosen. Conclusions pollution from urbanized regions in the Almada River reduces the evenness and diversity index of shannon, and increases the abundance of the zooplankton community.

Abstract: Aim The goal of this study was to investigate the effect of habitat heterogeneity on diversity on a local and regional scale. We tested two hypotheses: (i) the habitat diversity, given by quantity of microhabitat by macrophytes richness, increases the alpha diversity of organisms that live in those environments; (ii) the habitat heterogeneity, given by compositional difference of microhabitat, increases the beta diversity of organisms that live in those environments. Methods Samples contained cladocerans and macrophytes were collected in six wetlands from the Brazil Central during dry and rainy seasons, in Brazilian National Park (BNP) and Formosa Instruction Field (FIF). Results In local scale (wetlands) the number of macrophyte morphospecies shows the positive effect on alpha diversity of cladoceran; the compositional difference of the microhabitat positively affected the beta diversity in three wetlands studied. In regional scale, the number of macrophyte morphospecies showed the positive effect on alpha diversity; the beta diversity was higher in the BNP than in the FIF. Conclusions Our findings suggest that the species richness and dissimilarity of aquatic macrophytes increased to alpha and beta diversity of cladocerans on the local and regional scales. Thus, cladocerans richness was correlated with the number of microhabitats and the variability between microhabitats in wetlands.

Abstract: Aim In this study, we investigated the response of microcrustaceans composition, diversity and abundance (Cladocera and Copepoda) to the lake’s origin (natural and man-made) and trophic state (mesotrophic and eutrophic, with natural eutrophication and artificial eutrophication). We tested the following hypotheses: (I) the increase in the abundance of certain microcrustacean species may indicate a rise in the trophic level; (II) the richness and abundance vary amongst lakes and are higher in the lake with natural eutrophication; and (III) the microcrustaceans abundance is associate with high primary productivity, being higher in the eutrophic environment with artificial eutrophication. Methods The study was conducted in a segment of the Paranapanema River basin, in southeastern Brazil, focusing on five lakes spanning an eight-kilometer stretch, to understand the different organisms' responses to distinct conditions of aquatic environments. Sampling was carried out bimonthly over the course of a year. Results A principal component analysis (PCA) separated three types of lakes: eutrophic (natural and man-made) to mesotrophic. Additionally, 25 taxa were found. SIMPER analysis filtered six species with more than 70% dissimilarity contribution. Five species exhibited differences amongst the lakes, one species correlated with natural variables as depth. The redundancy analysis associated the Bosminopsis deitersi abundance with man-made eutrophic lakes and with the variables electrical conductivity, phosphorus, nitrogen, chlorophyll-a, and hardness. High abundances of B. deitersi indicated artificial eutrophication especially in man-made lakes, while natural lakes with natural eutrophication were not favorable environments for the increase of B. deitersi abundance. Conclusions This study highlights the neotropical oxbow lakes, emphasizing the significance of physicochemical characterization, detailed temporal sampling, and lake classification by origin and trophic level.

Abstract: Aim Considering the prediction capacity of the phytoplankton community, this study analyzed the environmental factors that influenced the Reynolds Functional Groups (RFG) in hydrological period (dry, rising, flood and ebb) and the type of environment (river and lake), in the Pantanal wetland (Brazil). We expect environmental variability to reflect in the predictive ability of phytoplankton to describe habitat types and flood-pulse periods, where the seasonality (high and low water) are the main drivers of phytoplankton distribution, biomass and functional groups. Methods We collected environmental variables and phytoplankton quarterly in 2018 from 18 points in the flood, rising, dry and ebb. Results recorded 425 taxa distributed into 13 taxonomic groups and 20 RFGs, of which nine groups (D, F, J, G, K, MP, N, S1, and P), represented by green algae, cyanobacteria, and diatoms, had the highest predictive value, characterizing lentic environments as rich in nutrients and light, and the Paraguay River as having a lower availability of these resources for phytoplankton. The variation in biomass was related to the phases of the flood pulse, being higher in low waters in floodplain lakes and smaller in high waters in the river. Conclusions Thus, the predictability of the phytoplankton community structure was directly associated with the environment types in the Pantanal wetland and with the homogenization or isolation of the systems promoted by the flood pulse that acted as drivers of phytoplankton distribution, biomass and functional groups.

Abstract The non-annual rivulid Melanorivulus decoratus is an endemic fish from the São Francisco River basin that was previously recorded only in small tributaries along river’s middle stretch in northwestern Bahia. The present record marks the first appearance of M. decoratus in the lower-middle São Francisco, approximately 450 km northeast of the closest previously documented site, providing an updated map of the species’ distribution. Currently classified as Least Concern (LC), this new occurrence record expands knowledge of the species’ range and conservation status.

Abstract Eutrophication control techniques primarily target the reduction of cyanobacterial biomass. However, it is crucial to consider the effects of these techniques on non-target planktonic organisms, as their dynamics and community structure are still not well understood. Aim The objective of this study was to perform a systematic review of the literature to observe the effects of chemical and physical eutrophication control techniques on planktonic organisms in eutrophic environments. It also aimed to evaluate bibliometric production and determine knowledge gaps. Methods The review was carried out based on the PRISMA methodology. The articles were searched in the databases of Scopus and Web of Science. The articles were screened so that only those within our objective remained. The systematic review was carried out with a final sample of 136 articles. Results The most frequently mentioned techniques were “Floc & Sink”, “Floc & Lock”, and algaecide application, (chemicals methods); aeration, dredging, and ultrasound (physical methods). There was an increase in the number of publications from 1974 until July 2020, especially on cyanobacteria. The identified gaps were studies on the zooplankton population and plankton community succession, and long-term experiments. All the chemical techniques remove cyanobacteria biomass or biovolume. Aeration, dredging, and ultrasound, which had conflicting results without conclusive findings. The few studies about the plankton community show positive effects on phytoplankton diversity after the “Floc & Sink” technique and an increase in richness after “Floc & Lock” and aeration. All the techniques negatively affect zooplankton, reducing biomass, survival, or abundance. Conclusions There are many studies on the effect of eutrophication control techniques on cyanobacteria, and they provide good removal of their biomass. However, there is a large gap regarding other phytoplankton taxonomic groups and zooplankton, making it difficult to draw definitive conclusions about the overall impacts of these techniques.