Acta Limnologica Brasiliensia

(681 Artigos indexados)

Effects of freezing on the carbon and nitrogen stable isotopic compositions of fish tissues - (2026)

Luciana Mulero Beloto, Thiago Simon Marques, Barbara Protocevich, Ronnie Von Mateus Ferreira, Plinio Barbosa de Camargo

Volume: 37 - Issue: 0

Resumo. Abstract Stable isotope analysis is a vital tool for elucidating nutrient flow within food chains. Studies utilizing this methodology must consider potential variables that could influence the δ13C and δ15N values of the species being examined. One such variable is the preservation of samples in a frozen state during field studies, particularly when immediate sample processing is not possible. Aim The objective of this study is to investigate the long-term effects of freeze-thaw at intervals of 1, 2, 7, 15, 30, 90 and 180 days on the δ13C, δ15N, and C:N ratios in biological samples from three fish species. Methods Tissues from three estuarine fish species (Cathorops spixii, Genidens barbus and Chloroscombrus chrysurus) were frozen and aliquots were subjected to thawing for sample collection aimed at isotopic determination. Results The discrepancies observed in this study were related to the δ13C and C:N ratios in the skin samples of C. spixii and G. barbus, as well as the muscle samples of C. chrysurus. These variations seem to be more closely linked to the potential volatility of the 12C isotope within the samples, resulting in δ13C enrichment and an increase in C:N values. Conclusions This suggests that these changes are not solely attributable to the freeze-thaw process, but may also be influenced by other factors like the lipid oxidation. Our findings suggest that this process significantly influences the δ13C and C:N ratios of skin and muscle tissues. Furthermore, we advocate for prompt processing of samples to minimize the impacts of freeze-thaw events.

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Extemporaneous environmental legislation: an analysis of the conflicts underlying Law 3824/1960 on coarse wood removal in Brazilian artificial reservoirs - (2026)

Lívia Helena Tonella, Oscar Barroso Vitorino Junior, Dilermando Pereira Lima Junior, Luiz Carlos Gomes, Fernando Mayer Pelicice, Angelo Antonio Agostinho

Volume: 32 - Issue: 0

Resumo. Abstract This article discusses the purpose and effects of Law 3824/1960, which makes mandatory the removal of vegetation and consequent cleaning of land sites subject to flooding by the construction of artificial reservoirs. The importance of this reflection is to avoid having a law that is considered effective, though if questioned, may prove contrary to the objectives for which it was created. Thus, this article aims to awaken decision makers to the possibility that this law is considered inapplicable to the current reality, according to the social, scientific, legal and environmental advances achieved in recent years. As a specific objective, based on the findings obtained, we aim to stimulate authorities to act in favor of the elaboration of a law that will meet these advances.

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Seasonal variation on diet of juvenile Elops saurus Linnaeus, 1766 (Ladyfish) in the Parnaiba River Delta - (2026)

Tatiane Araujo Santos, Thamires Souza Gonçalves, Patricia Silva do Nascimento, Cézar Augusto Freire Fernandes, Francisca Edna de Andrade Cunha

Volume: 32 - Issue: 0

Resumo. Abstract: Aim Identify seasonal variations in the diet of juvenile living in the estuary of the Parnaíba River Delta. Methods Food items were identified through analysis of stomach contents, and later submitted to analysis by regular methods for Frequency of Occurrence (FO), Frequency Numerical (FN), Gravimetric Frequency (FW) and Relative Importance Index (IRI). Results Juvenile diet of Elops saurus that inhabit the lagoons in the Parnaíba delta was composed in order decreasing of importance by Osteichthyes (Teleostei), Insecta and Crustacea in addition to Polychaeta and Nematoda. It was also observed a high frequency of occurrence of fragments of plastics in the diet. In the rainy season, 17 items were recorded in the diet, whereas in the dry season only 7 items were present. Relative Importance Index showed high presence of the Teleostei fish (69.93%) on diet of E. saurus during the rainy season, whereas during the dry period the insects of the families Corixidae (43.25%) and Dysticidae (39.16%). Conclusions With the study it was possible to identify that juvenile are piscivorous in the rainy season when there is a higher availability of prey in the environment and insectivores in the dry season when it reduces the supply of food, indicating feeding flexibility to environmental alterations.

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Advances and limitations of using satellites to monitor cyanobacterial harmful algal blooms - (2026)

Igor Ogashawara

Volume: 31 - Issue: 0

Resumo. Abstract The use of satellites for monitoring forests is common and well-known practice. However, the operational remote monitoring of water quality from space is still under development. In the United States of America (USA), the use of this type of data is just now being applied to operationally monitor cyanobacterial harmful algal blooms (CHABs). This powerful tool can be used to generate temporal and spatial assessments of CHABs, however the validation of the retrieved information is still a challenge - especially in tropical and equatorial countries. This commentary discusses the advantages and challenges of current initiatives that use Earth Observation data for managing CHABs such as “Lake Erie’s HAB Bulletin” and “Project CYAN” - both in the USA. Additionally, it was also discussed the application of remote sensing techniques to monitor CHABs in Brazilian inland waters.

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Advancing impact evaluation in applied limnology - (2026)

Luiz Guilherme dos Santos Ribas, André Andrian Padial, Luis Mauricio Bini

Volume: 31 - Issue: 0

Resumo. Abstract Accurate impact evaluations of different interventions are paramount in environmental sciences. In this context, the main challenge is to identify causal relationships to understand how different interventions affect the systems of interest. For this task, the counterfactual thinking can be used to estimate the impacts of interventions on the real scale of the problem using observational data. By definition, counterfactuals are states contrary to facts. In the context of interventions, they are the states of the units of analysis in the absence of intervention. This approach allows one to estimate the impact more accurately by comparing the differences between factual and counterfactual states. In this essay, we present some basic elements of the counterfactual thinking and discuss how it, based on experiences in other areas (e.g., medicine and economics), may be useful for the research of complex problems in aquatic ecology.

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Allelopathic effects of the aquatic macrophyte Ceratophyllum demersum L. on phytoplankton species: contrasting effects between cyanobacteria and chlorophytes - (2026)

Cihelio Alves Amorim, Rafael Henrique de Moura-Falcão, Celina Rebeca Valença, Vitor Ricardo de Souza, Ariadne do Nascimento Moura

Volume: 31 - Issue: 0

Resumo. Abstract Aim To assess the allelopathic effects of the submerged macrophyte Ceratophyllum demersum on four strains of phytoplankton species: two cyanobacteria (Microcystis aeruginosa - microcystin producing and M. panniformis - non-microcystin producing), and two chlorophytes (Ankistrodesmus falcatus and Raphidocelis subcapitata). Methods A coexistence experiment between C. demersum and the four strains was carried out for six days, with eight treatments and three replicates. The strains were cultivated in ASM1 culture medium, under controlled laboratory conditions. Two treatments were assigned for each strain, one with 6 g.L-1 of the macrophyte, and the control without the plant. Biomasses and growth rates of the strains were evaluated every two days, which were compared through the T-test and two-way ANOVA, respectively. Results The results varied among the strains, with toxic M. aeruginosa being intensely inhibited by C. demersum, with a decrease of 99.5% in its biomass (p<0.001), while non-toxic M. panniformis was less affected by the allelochemicals, with a reduction of 86.2% (p<0.001). Ankistrodesmus falcatus delayed its growth when in coexistence with the macrophyte, decreasing its biomass in 50.4% (p<0.01), while R. subcapitata was not altered (p>0.05). In coexistence with C. demersum, M. aeruginosa exhibited the lowest growth rates (-0.65 d-1), followed by M. panniformis (-0.15 d-1), A. falcatus (0.19 d-1), and R. subcapitata (0.34 d-1), with significant differences between all strains (p<0.001). Microcystis aeruginosa presented higher inhibition rates than M. panniformis (p<0.001), as well as, A. falcatus was more inhibited than R. subcapitata (p<0.05). Conclusions The presence of microcystins could influence the allelopathic responses of C. demersum, that may release more allelochemicals in coexistence with toxic strains of M. aeruginosa. Accordingly, C. demersum can be used in biomanipulation strategies to control toxic and non-toxic cyanobacterial blooms, without damaging other phytoplankton species, like chlorophytes.

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Big things come in small packages: why limnologists should care about small ponds - (2026)

Melissa L. Mullins, Robert D. Doyle

Volume: 31 - Issue: 0

Resumo. Abstract There is a substantial, and increasing, body of evidence that small ponds are critically important in diverse landscapes around the world by providing habitat, processing carbon, and mediating hydrological and nutrient fluxes to other larger surface waters (rivers, lakes, coastal). They are also among the most abundant surface water bodies in many areas. In an urbanizing planet, ecosystem services provided by ponds may become even more important. However, they have been historically neglected by limnologists and including them in global analyses can still be problematic. We propose that more limnologists should include small ponds in research programs; and we argue that these are also ideal systems for teaching the next generation of limnologists as well as for engaging the public.

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Biomass and abiotic variables change in phytotelmic environment in the tank-bromeliad Nidularium longiflorum Ule in tropical forest - (2026)

Karina Margaret Silva das Neves, Armando Reis Tavares, llka Schincariol Vercellino, Carla Ferragut

Volume: 31 - Issue: 0

Resumo. Abstract Aim Phytotelm plays an important role in plant growth and ecosystem functioning, but this natural aquatic microcosm is poorly known. We evaluated the seasonal (dry and rainy seasons) and spatial variations (forest trail and stream sites) of the phytotelm in Nidularium longiflorum, bromeliad that occurs in the Atlantic Forest. Methods Abiotic and biotic variables were measured in tank-bromeliad phytotelms. The biomass was analyzed by ash-free dry mass and chlorophyll-a concentration. Results Abiotic variables measured in the phytotelmic environment of bromeliads varied between sampling sites and seasons. Temperature, electrical conductivity and total nitrogen values were significantly different between seasons and sites. Chlorophyll-a and ash-free dry mass (organic matter) in phytotelm were significantly different between sampling sites. Eleven genera of algae in the phytotelm were identified. PCA axis 1 ordination evidenced the seasonal variation of environmental conditions. Conclusions Our findings suggest that environmental and micro-environmental conditions do not favor the development of algal community in the phytotelm. Biomass and abiotic variables in phytotelm of Nidularium longiflorum change seasonally, however biomass accumulation was strongly influenced by site characteristics.

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Habitat, limnological signatures and spatial modeling: a zoning proposal for the Curuá-Una hydroelectric reservoir, Pará, Brazil - (2026)

Juciley de Almeida Santos, Keid Nolan Silva Sousa, Paulo Roberto Brasil Santos, Joelson Leal de Lima, Rivolo de Jesus Bacelar

Volume: 31 - Issue: 0

Resumo. Abstract Aim The objective of this work is to characterize, spatially model and to perform the zoning of the aquatic environment in the Curuá-Una HPP reservoir, in the state of Pará, in the Brazilian Amazon. Methods The data were collected from 77 sampling points distributed over 20 transects in the Curuá-Una reservoir, in November 2016. The data were obtained through descriptive templates of the landscape, and assessment of limnological, bathymetry and georeferencing variables. To describe and model spatial patterns for the limnological Proxies, geostatistical analysis was used with semivariogram fitting, and interpolation using Ordinary Kriging to generate the maps. To determine the degree of association of the landscape Proxies, Correspondence Analysis (CA) was chosen, and to relate the landscape Proxies with the limnological Proxies, Canonical Correspondence Analysis (CCA) was carried out. Results The results of the analysis of the limnological Proxies showed that the variables presented normal distribution according to the Shapiro-Wilk test (5%) except for transparency and temperature. Most of the variables obtained well-defined, level and good geostatistical analysis. There was a prevalence of gaussian and spherical adjustment models. Different zones in the distribution of the limnological variables in the longitudinal axis of the reservoir were observed. The CA showed a short local gradient in the variables, which effectively characterizes the interface of landscape and human. In Figure 5, the first two axes of the CCA showed 61.17% of the data variability. The limnological signatures showed 42.3% of variability, with high correlation between the landscape Proxies and the environmental Proxies in both axes. Conclusions This type of approach should be useful in managing Brazilian river basins, especially in the Amazon, a focus for the construction of numerous hydroelectric dams, as it can indicate the limnological and environmental state and provide a clearer view of these environments.

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Longitudinal dimensions of land-use impacts in riverine ecosystems - (2026)

Rafael Feijó-Lima, Eugenia Zandonà, Bruna Suelen da Silva, Flavia Tromboni, Timothy Peter Moulton, Steven Arnold Thomas

Volume: 31 - Issue: 0

Resumo. Abstract: Aim Rivers are linked longitudinally via the flow of water and the spatial dimensions of the changes in local riparian vegetation are still poorly understood. Recent modifications to the Native Vegetation Protection Law allow reduction of lateral buffer strips and amnesty for riparian vegetation removal, which might increase the fragmentation of native riparian vegetation, especially for Atlantic Rainforest streams. Methods We present two case studies conducted in a stream draining a fragmented landscape in the Atlantic Rainforest. The stream flows through two abrupt transitions (forest-pasture-forest) and we investigated how far the upstream effects of a given riparian condition could be detected in the downstream reach for a suite of variables. Results We show that the effects of land cover propagate downstream for both algal and macroinvertebrate communities. For some variables of interest, these effects might extend up to a km downstream from the transition. Conclusions There is a need to understand how the distribution of riparian forest remnants contribute to maintaining watershed-scale resilience to impacts.

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Mollusks associated with the Avicennia schaueriana (Magnoliophyta: Acanthaceae) roots of a hypersaline estuary in northeastern Brazil - (2026)

Ana Priscila Amancio Muniz, Rafaela Cristina de Souza Duarte, Ellori Laíse Silva Mota, Jessica de Oliveira Lima, Thelma Lúcia Pereira Dias

Volume: 31 - Issue: 0

Resumo. Abstract Aim Avicennia schaeuriana is one of the six species that composes the mangrove forests of Brazil and form mangrove fringes along waterways. The mangrove-roots of the A. schaeuriana act as one of the microhabitats used by the invertebrate biodiversity of the estuarine ecosystem. The present note aimed to inventory the malacofauna associated with roots of Avicennia schaueriana of the hypersaline and inverse estuary, highlighting variations in abundance and diversity along a salinity gradient and different seasonal periods. Methods Three sampling stations were delineated along the course of the estuary. At each station 3 transects of 10 meters were placed, and for each of them 3 sample points were selected, and at each point 3 samples of roots of A. schaueriana were obtained. A total of 108 samples were stored in plastic bags containing 4% formaldehyde and subsequently passed through a screening process, with identification of the associated specimens with the lowest possible taxonomic level. Results A total of 171 specimens was recorded, belonging to 10 species, 7 families, and 9 genera of the Bivalvia and Gastropoda classes. The abundance of the specimens differed between the seasonal periods analyzed. Conclusions The highest species richness and abundance of organisms in the rainy period allows inferences about the importance of the estuarine water cycle in regulating the biodiversity of these environments. Thus, the importance of the maintenance and protection of the mangrove forests composed of A. schaueriana, as well as the need for more in-depth studies becomes evident.

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Monitoring simplification in plankton communities using different ecological approaches - (2026)

Carla Albuquerque de Souza, Karine Borges Machado, João Carlos Nabout, Daphne Heloisa de Freitas Muniz, Eduardo Cyrino Oliveira-Filho, Cleber Nunes Kraus, Rômulo José da Costa Ribeiro, Ludgero Cardoso Galli Vieira

Volume: 31 - Issue: 0

Resumo. Abstract Aim This study aimed to answer: (i) can phytoplankton communities be used as surrogate of zooplankton communities?; (ii) can we use ecological approaches like functional groups (FG) or morphofunctional classification (MBFG) as surrogate for phytoplankton species?; (iii) can we use substitute groups (cladocera, copepod, rotifer or testate amoebae) as surrogate for zooplankton species?; (iv) are the environmental variables’ ordination standards concordant with the ordering patterns of phytoplankton and zooplankton species?; and (v) for both communities, is the spatial pattern of ordination maintained using density data or presence/absence of individuals or lower taxonomic resolutions? Methods The study was conducted in 25 water bodies that supply central-pivot irrigation in the Federal District - Brazil (Rio Preto Basin), in October 2012. We evaluated some physical and chemical variables as well as phytoplankton and zooplankton samples. To evaluate correlation among biological groups, numerical and higher taxonomic resolutions, we performed some Mantel and Procrustes analyses. Results Evaluating the use of substitute groups, comparisons between phytoplankton and zooplankton, FG and MBFG classifications and almost all the comparisons between zooplankton groups suggested concordant patterns. However, the values of r were low, all below 0.70. Biological analyses with phytoplankton and zooplankton can be performed using presence/absence of individuals without significant loss of information, except for MBFG classification and copepods. Data may also be used at genus or family level for copepods and testate amoebae and only data at genus level for cladocerans and rotifers. Different results were found concerning taxonomic resolution for phytoplankton considering that, while being significant, the r value was less than 0.70. Conclusions For environmental monitoring purposes, it is important to sample both phytoplankton and zooplankton communities because one is not surrogate of the other one, in the same way as phytoplankton density and their functional and morphofunctional approaches. On the other hand, to simplify the environmental monitoring, it is possible to adopt presence/absence species data instead of abundance data for both zooplankton and phytoplankton communities, except for copepods and morphofunctional approach. It is also possible to adopt genera level for zooplankton community and family level for copepods and testate amoebae.

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Nutritional value changes in response to temperature, microalgae mono and mixed cultures - (2026)

Frederico Pacheco Militão, Valéria de Oliveira Fernandes, Kathiani Victor Bastos, Aline Paternostro Martins, Pio Colepicolo, Levi Pompermayer Machado

Volume: 31 - Issue: 0

Resumo. Abstract Aim The response of mixed cultures and monocultures of Pseudopediastrum boryanum (Turpin) E. Hegewald and Scenedesmus obliquus (Turpin) Kützing was assessed in the laboratory at three different temperatures: 20, 30 and 40 °C. The change in biomass and biochemical composition of these cultures was evaluated. Methods Microalgae were placed in a batch culture over 21-days in ASM1 medium. Cell density was directly counted every two days using a Fuchs-Rosenthal hemocytometer. Chlorophyll ‘a’ and total carotenoids were extracted twice. Protein, carbohydrate, total lipid and fatty acid contents were determined at the end of the experiment. Results Cultures grown in 40 °C exhibited no growth. However, there was increased cell density (13.6 x 106 cell.mL-1) and biomass (55 g.L-1) in the S. obliquus monoculture at 30 °C. High protein concentrations (672.6 mg.g-1) were observed in monocultures P. boryanum and S. obliquus at 20 °C treatments. There were high carbohydrate concentrations (6.17 mg.g-1) in P. boryanum unialgal at 30 °C. There was no significant difference in total lipid content between S. obliquus (95.5 mg.g-1), P. boryanum (96.3 mg.g-1) and the mixed culture at 20 °C (105.3 mg.g-1). FAMEs varied significantly regarding the number of unsaturated components, which predominantly consisted of fatty acids with two or more unsaturated bonds. Conclusions The biomass of the treatments analyzed was rich in proteins and essential fatty acids (such as linolenic acid), yet low in carbohydrate content, suggesting its potential use as a food supplement. Our results indicate that mixed culture of P. boryanum and S. obliquus was inefficient in cultivating biomass or biochemical compounds as compared to the unialgal cultivations. However, algae grown together showed better stability in their biochemical composition in response to changes in temperature, an important factor for microalgae production in open ponds and in food safety measures. These results suggest the consortia among different species of microalgae should be tested to determine better methodologies for the production of biomass and metabolites with greater stability towards environmental factors.

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Post-fire consequences for leaf breakdown in a tropical stream - (2026)

Renan de Souza Rezende, Cristiano Queiroz de Albuquerque, Andrezza Sayuri Victoriano Hirota, Paulo Fernandes Roges Souza Silva, Ricardo Keichi Umetsu, Helena Soares Ramos Cabette, Paulino Bambi, Natália Guedes, Cássia Alves Lima-Rezende, José Francisco Gonçalves-Júnior

Volume: 31 - Issue: 0

Resumo. Abstract Aim Wildfire is a natural pulsed disturbance in landscapes of the Savannah Biome. This study evaluates short-term post-fire effects on leaf litter breakdown, the invertebrate community and fungal biomass of litter from three different vegetal species in a tropical stream. Methods Senescent leaves of Inga laurina, Protium spruceanum and Rircheria grandis (2 ± 0.1 g dry mass) were individually placed in litter bags (30 × 30 cm: 10 mm coarse mesh and 0.5 mm fine mesh) and submerged in the study stream before and after fire. Replicate bags (n = 4; individually for each species, sampling time, fire event and mesh size) were then retrieved after 20 and 40 days and washed to separate the invertebrates before fire event and again immediately after fire. Disks were cut from leaves to determine ash-free dry mass, while the remaining material was oven-dried to determine dry mass. Results The pre-fire mean decomposition coefficient (k = -0.012 day-1) was intermediate compared to that reported for other savannah streams, but post-fire it was lower (k = -0.007 day-1), due to decreased allochthonous litter input and increased autochthones production. Intermediate k values for all qualities of litter post-fire may indicate that fire is equalizing litter quality in the stream ecosystem. The abundance of scrapers was found to be more important than fungal biomass or shredder abundance, probably due to their functioning in leaf fragmentation while consuming periphyton growing on leaf litter. Conclusions Theses results indicate that fire can modify the relationships within decomposer communities in tropical stream ecosystems.

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Spatial and temporal trends in freshwater fish research: the case of three neotropical river basins from Goiás State, Central Brazil - (2026)

Rodrigo Assis Carvalho, Francisco Leonardo Tejerina-Garro

Volume: 31 - Issue: 0

Resumo. Abstract Aim In this paper, we conducted a scientometric analysis on published studies related to freshwater fish species at Goiás State to evaluate: i) their spatial and temporal trends; ii) areas of knowledge; iii) scientific journals where these papers were published and their comprehensiveness; iv) the role of institutions and financial support on fish research. Methods Using Google Scholar and Lattes platform, we searched for scientific papers related to freshwater fish, and we extracted the following information of each paper: title, author and co-authors’ name, number of authors, year, authors and co-authors’ affiliation, journal, field/area of the research, and financial support. Results We found 322 scientific papers related to Goiás State with a slightly growth in the number of publications over time. Most of these papers are related to Ecology, Systematic/Taxonomy and Fish Biology, and the participation of local institutions in these studies was mainly concentrated in Paraná River basin. Although most of funding were granted by agencies or institutions located outside Goiás State, the results showed that fish papers achieved a broad audience with publications in national and international journals with impact factor. Conclusions Our study revealed that: 1) freshwater fish research at Goiás State has a slow increase trend; 2) there are gaps in Education, Conservation and Fisheries knowledge areas; 3) local institutions’ contribution is spatially concentrated; 4) studies achieved a broad audience with many scientific papers published in journals with impact factor; 5) financial support was granted in most part by agencies or institutions located outside Goiás State. These findings suggest that despite achievements in freshwater fish research in this region, local investments in infrastructure, materials and human resources are still necessary to improve the production of studies.

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The Ecology and Conservation of Wild Rice, Zizania palustris L., in North America - (2026)

David Dean Biesboer

Volume: 31 - Issue: 0

Resumo. Abstract Wild rice is an enigmatic plant species in the upper northern Midwestern U.S. Wild rice (Zizania palustris L.) is widespread in the region. However, it is both a wild species and a semi-domesticated crop. It is enigmatic because it is grown and harvested by machine in large paddies by commercial farmers but wild populations are considered to be important spiritually to native Americans in the United States. Native Americans and the public harvest wild rice by hand and sell and trade it on a local basis. This has caused a political controversy between people who consider wild rice to be a crop belonging only to native Indian bands and those who consider that it belongs to citizens of the U.S. Conservation of populations of wild rice has become politically difficult because of these contrasting views. This paper discusses this controversy and addresses the difficulty of conserving this economically widespread plant that is under ecological pressure in modern times.

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The role of sediments in the carbon and pollutant cycles in aquatic ecosystems - (2026)

Simone Jaqueline Cardoso, Gabrielle Rabelo Quadra, Nathália da Silva Resende, Fábio Roland

Volume: 31 - Issue: 0

Resumo. Abstract Aim Anthropogenic modifications in the landscape are accelerating biogeochemical cycles and causing unbalances in terrestrial and aquatic ecosystems with still unknow impacts on biotic and abiotic processes. Therefore, there has been increasing scientific interest in the links between human activities and ecosystems functions. Methods Here we review the role of aquatic sediments in the carbon and pollutant cycle. Results We briefly explore the historical context, origin, and composition of the sediments, as well as the factors that influence the processes of carbon and contaminants cycling and the role of sediments in the greenhouse gases emissions in aquatic ecosystems. Conclusions Aquatic sediments can help to understand the terrestrial and aquatic ecosystem changes, once they are good sentinels, reflecting key biogeochemical processes over time.

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The structuring role of macrophytes on plankton community composition and bacterial metabolism in a large subtropical shallow lake - (2026)

Ng Haig They, David da Motta Marques

Volume: 31 - Issue: 0

Resumo. Abstract Aim We aimed at investigating changes in major groups of plankton (bacterioplankton, phytoplankton and zooplankton) and bacterioplankton metabolism along a transect covering a littoral, macrophyte dominated zone to a pelagic, phytoplankton dominated zone in the large subtropical shallow lake Mangueira, Rio Grande do Sul State, Brazil. Methods The 3.2 km littoral-pelagic transect (7 points) was sampled in October 2007 in the southern section of the lake. Major taxonomic groups of phytoplankton and zooplankton were counted and identified by optic microscopy. The bacterioplankton was identified by FISH (Fluorescent in situ Hybridization), and bacterial abundance, biovolume and biomass were quantified by epifluorescence microscopy. Primary and bacterial productions were measured by incorporation of radioactive bicarbonate and leucine, respectively. Bacterial respiration was measured by experiments of oxygen consumption, and an extensive data set of limnological variables were measured through standard methods. Results Sharp changes in chemical/physical variables, as well as in bacterial density, biovolume, biomass and bacterial growth efficiency occurred on average at 30% of macrophyte coverage, with most of them increasing towards pelagic zones. The composition of major groups of zooplankton, phytoplankton, bacterial morphotypes and phylotypes indicated that different planktonic assemblies live apart in these two zones. Conclusions Our results demonstrate that macrophytes are a structuring driver of the plankton community and bacterial metabolism in this large subtropical shallow lake.

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Tunnel vision in current chemicals management cannot deal with the unknown risk of synthetic chemicals in aquatic systems - (2026)

Anna Sobek, Emma Undeman

Volume: 31 - Issue: 0

Resumo. Abstract Chemicals management is focused around the hazard, exposure and risk assessment of single chemicals. This is a slow process which cannot keep pace with chemical innovation and development of use. Environmental monitoring focuses on few, and well-known, chemicals. As a consequence, the majority of all chemicals emitted to the aquatic environment remain unstudied, and so does their risk. We conclude that to understand how chemical pollution affects aquatic ecosystems, requires reformation of current chemicals management, moving away from the single chemical approach. It requires increased transparency regarding chemical content in materials, products and articles, and importantly, a management system that covers different aspects of the many unknowns related to chemical pollution of aquatic systems. This implies for instance, environmental monitoring that screens for a wide range of chemicals and effects, and that is able to detect more unexpected effects of chemical pollution than what is possible today.

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Wastewater infrastructure and the ecology and management of freshwater systems - (2026)

Krista Arminty Capps

Volume: 31 - Issue: 0

Resumo. Abstract Globally, freshwater resources are influenced by inputs of energy, nutrients, and pollutants from human wastewater. Local resource managers and policy-makers are tasked to address ecological and human-health concerns associated with aging and obsolete water infrastructure using limited financial resources. Nevertheless, there is limited information available describing how waste streams vary in their pollutant load or their subsequent effects on ecosystem structure and function in streams and rivers. Consequently, as wastewater systems degrade, local resource managers and policy makers are forced to develop watershed management strategies to deal with increasing effluent discharge without an understanding of how their decisions will influence local ecological processes or the structural and functional integrity of downstream habitats. Here, I discuss some of the ecological implications of obsolete or absent wastewater treatment, and describe how mismatches between the governance of wastewater management and watershed ecology may exacerbate environmental problems.

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A decade of invasion: distribution patterns and temperature influence on Kellicottia bostoniensis (Rousselet, 1908), in the Upper Uruguay River Basin - (2025)

Michelle das Neves Lopes, Lorena Pinheiro-Silva, Lucas Garbo Miguel, Claudia Costa Bonecker, Grasiela Fagundes Cardoso, Alex Pires de Oliveira Nuñer, Nei Kavaguichi Leite, Maurício Mello Petrucio

Volume: 37 - Issue: 0

Resumo. Abstract: Aim This study reports the spread dynamics of the non-native species Kellicottia bostoniensis across all reservoirs in the Upper Uruguay River Basin, a decade after its initial recorded occurrence. Additionally, it assesses the role of temperature in shaping its distribution within this subtropical system. Methods Spatial and temporal variations in K. bostoniensis density and environmental parameters were analyzed over a 12-month period. Generalized Linear Models (GLMs) were applied to evaluate the relationship between environmental parameters and species density, providing insights into the key drivers of its distribution. Results The connectivity among reservoirs within the cascade system of the Upper Uruguay River has facilitated the continued spread of the non-native species K. bostoniensis. The detection of this species in all reservoirs a decade after its first recorded occurrence suggests its successful establishment and widespread distribution within the system. The observed high densities were likely influenced by the consistently low temperatures characteristic of subtropical regions, particularly those associated with the Serra Geral Mountains, with a more pronounced effect during colder months. Conclusions The widespread distribution of K. bostoniensis across the Upper Uruguay River Basin underscores its potential for further expansion into similar environments, driven by a combination of environmental and anthropogenic influences. The species’ ability to disperse and establish in diverse habitats highlights the critical need for continuous monitoring and management strategies to mitigate its spread and prevent additional ecological invasions.

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A record of pughead deformity in Satanoperca jurupari (Heckel, 1840) (Teleostei: Cichlidae) in the Lower Rio Tocantins Basin - (2025)

Lais Lobato Jacob, Felipe Arian de Andrade Araújo, Renan Leão Reis, Júlia Gabrielle Carvalho Nascimento, Alberto Akama

Volume: 37 - Issue: 0

Resumo. Abstract: The pughead condition is a cranial deformity characterized by a shortened upper jaw relative to the lower jaw. In this study, we report the occurrence of this deformity in a single specimen of the Demon Eartheater, Satanoperca jurupari, collected in the Lower Rio Tocantins Basin. The most affected anatomical regions include the upper jaw, suspensorium, and anterior portion of the neurocranium. Although pollution from agrochemicals used in palm monoculture near the collection site is a plausible contributing factor, no direct evidence currently confirms this as the cause. This report represents the first documented case of the pughead condition in Satanoperca and the first record of this deformity in a species from rivers of the Brazilian Shield.

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A systematic review of the water quality in the Doce River Basin: following the Fundão dam collapse - (2025)

Bianca Loureiro do Valle, Lorena Torres Oporto, Diego Guimarães Pujoni, José Fernandes Bezerra-Neto

Volume: 37 - Issue: 0

Resumo. Abstract: Aim The Doce River Basin has a high ecological and socioeconomic relevance. This basin faces considerable challenges, especially after the Fundão dam collapse in 2015, which contaminated the river system with iron ore tailings, impacting the river's biota and the communities that depend on it. This study aimed to identify thematic patterns, knowledge gaps, and temporal trends in scientific production based on a systematic review and scientometric analysis of water quality studies. Methods This study searched for articles focusing on the basin using the Web of Science and Scopus databases, following the PRISMA criteria for systematic reviews. Articles published up to December 2024 were included, using terms related to water quality and the Doce River Basin and its main tributaries. In addition, temporal trend analysis and thematic categorization of the studies were conducted. Results A total of 88 studies were identified, 76 of which were published after the disaster, with an emphasis on metal and metalloid concentrations, followed by physicochemical indicators such as pH and conductivity. In contrast, nutrients, emerging contaminants, and bioindicators were significantly less addressed. There are critical gaps in the assessment of chronic impacts such as changes in land use and effluent discharge, which could potentially hinder the assessment of the effects of dam failure. In addition, most tributaries remain poorly studied. Conclusions Scientific production increased substantially after the disaster but remained concentrated on specific themes and regions. Expanding the geographic and thematic scope, as well as integrating biological indicators and chronic contaminants, is essential to support conservation policies and the integrated management of water resources in the basin.

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Aquatic macrophytes in Amazon: review, knowledge and gaps - (2025)

Antônio Augusto de Souza Costa, Nayara Louback Franco, Raimundo Luiz Morais de Sousa, Ana Luísa Biondi Fares, Flávia Alessandra Silva Nonato, Rayssa Silva Carmo, Marcelle Fernanda Oliveira Barbosa, Thaisa Sala Michelan

Volume: 37 - Issue: 0

Resumo. Abstract: Aim The Amazon region presents peculiarities in its hydrology and vegetation, which are essential for climate balance. For this reason, the Amazon requires better sampling of its biodiversity, thus increasing knowledge of the organisms present in this area. In this study, through a systematic review, we evaluated to assess the advances in ecological theories research and we verified the stages of macrophyte biodiversity research in the Amazon. Methods We used databases available on Web of Science and Scopus. The keywords used for the search were: amazon, macrophytes, and aquatic plant. The designated research period was between 1970 and 2022. The processed data were grouped into specific types according to the object of study. Results Our results showed that the majority of studies addressed the influence of aquatic macrophytes on aquatic organisms (e.g., fish, insects, plankton, and manatees), as well as their influence on the abiotic characteristics of aquatic environments in the Amazon forest. Studies mostly focused on the relationship between macrophytes and other organisms or environmental variables. Conclusions We identified research gaps in ecological and biological invasion studies with macrophytes in the Amazon and highlight the importance of international cooperation and scientific production for ecosystem conservation.

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Asymmetric dispersal in freshwater species distribution models varies depending on the spatial pattern of fish species - (2025)

Micael Rosa Parreira, João Carlos Nabout

Volume: 37 - Issue: 0

Resumo. Abstract: Aim We estimated the relative contribution of environmental and dispersal predictors in distribution models of freshwater species with different distribution ranges (29 fish species). Specifically, we tested whether model performances vary depending on the fish species' range and distribution across sub-basins and whether the relationship with those predictors is stronger depending on the type of variables (environmental or asymmetrical dispersal) used for modeling. Methods The study area used for modeling was the Tocantins-Araguaia River basin, encompassing the entire hydrographic network. We applied six niche modeling methods to project the geographic distributions of 29 fish species within the Tocantins-Araguaia River basin, using environmental and asymmetrical dispersal predictors. Results Generally, the models built using dispersal predictors generated more accurate predictions than those using environmental variables. However, although we found no significant difference in the accuracy among models built using different variables, their accuracy metrics were correlated with the species range and distribution across sub-basins. Also, more restricted species (i.e., lower range and distribution limited to one sub-basin) showed a greater difference in model accuracy between models built using dispersal and environmental predictors, with more accurate models being generated for restricted species when modelled using dispersal-related predictors only. Conclusions the use of asymmetric dispersal predictors in SDM, besides generating accurate models, avoids/reduces model overpredictions to geographically close and climatically suitable areas, especially for restricted species, by predicting the species’ distribution based on their dispersal routes through the actual directional gradient of the basin’s hydrographic network.

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