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Eutrophication is recognized as the main water quality problem worldwide, mainly due to the prevalence of harmful cyanobacterial blooms. Submerged macrophytes can control cyanobacterial biomass by removing nutrients from the water column or producing allelopathic compounds. As a result, they are highlighted as a potential strategy for restoring eutrophic waters. However, studies in semi-arid tropical ecosystems have shown inconsistent results regarding the effects of submerged macrophytes on cyanobacterial communities and cyanotoxin production. The aim of this study was to assess the effect of submerged macrophytes on cyanobacterial community structure and microcystin production in a tropical semi-arid reservoir subject to intense periods of water level drawdown. Submerged macrophyte cover, surface water physical and chemical variables, cyanobacterial community biovolume and microcystin concentration were measured monthly between October 2014 and July 2015 at the entrance of the river (Zone I) and dam zones (Zone II) of a reservoir. Although both zones were dominated by the submerged macrophyte Egeria densa, there were significant differences in macrophyte cover: Zone I had greater submerged macrophyte cover and Zone II had lower submerged macrophyte cover. Higher total cyanobacterial biovolume, potential microcystin producer biovolume and microcystin concentrations were observed in the zone with the greater submerged macrophyte cover. Moreover, our results showed that nutrient concentrations (total phosphorous, total nitrogen and ammonium) and physical variables (water temperature and turbidity) were also associated with the zone with greater submerged macrophyte cover. This study highlights that the water level drawdown of the reservoir appears to have favored an increase in nutrient concentration, especially in the zones with dense vegetation, which may have contributed to the coexistence of the high cyanobacteria biomass, high submerged macrophyte coverage and high microcystin concentration. Thus, developing strategies for the management of submerged macrophyte cover during water level drawdown events is essential for improving water quality and reducing the risk of harmful cyanobacterial blooms at the ecosystem level in tropical semi-arid aquatic ecosystems.

Este trabalho avalia indicadores de produtividade científica do corpo docente da Universidade Estadual da Paraíba (UEPB), entre os anos de 2011-2015. Um total de 911 currículos Lattes foram avaliados quanto ao número de publicações de livros, capítulos de livros, artigos, fomento (bolsistas PQ), título acadêmico, participação em programas de pós-graduação (PPG) e a soma de orientações concluídas a discentes de graduação e pós-graduação. Contabilizou-se um total de 3.816 artigos, 383 livros e 1.257 capítulos de livros. 55,8% dos artigos foram publicados pelos docentes integrantes da pós-graduação. 14 docentes são detentores da bolsa produtividade CNPq. 290 docentes não tiveram nenhuma publicação científica no período analisado. Os pesquisadores das áreas das Ciências da Saúde e Ciências Biológicas apresentaram uma maior produção científica quanto à publicação de artigos em periódicos. As áreas de Ciências Humanas e Ciências Sociais Aplicadas tiveram a maioria de suas publicações associadas a livros e capítulos de livro em editoras nacionais. O maior número de publicações em revistas indexadas em bases internacionais está associado a docentes vinculados aos Departamentos de Biologia e de Enfermagem. Constata-se que a produção científica está concentrada em uma minoria de docentes, especialmente aqueles ligados a algum programa de pós-graduação, sobretudo os docentes pertencentes às áreas de Ciências Biológicas e Ciências da Saúde.

We provide the first record of Xiphophorus maculatus (Günther, 1866) in a river basin in the northeastern Brazil. Specimens were collected in the Jaguaribe River basin, João Pessoa, Paraíba state, Brazil. Two hundred eighty-one specimens, corresponding to 143 males and 138 females of X. maculatus, were collected at nine sites along the basin, from 2017 to 2019. Specimens total length ranged from 17.5 to 26.6 mm in males and from 11.7 to 32.7 mm in females. Introduction of non-native species greatly threatens the biological diversity worldwide. When introduced into a new habitat, X. maculatus usually decreases microcrustacean, macroinvertebrate and native fish populations.

Os padrões de distribuição e abundância das espécies são regidos por um conjunto de condições ambientais que delineiam as áreas apropriadas para o estabelecimento e manutenção das populações, funcionando como filtros ambientais. Levando isto em consideração, este trabalho teve como objetivo comparar as estruturas da comunidade fitoplanctônica (composição e abundância) entre um ambiente lótico e um lêntico, que são conectados em cascata, e compreender quais fatores ambientais melhor explicam a estruturação dessas comunidades. Para isto, foram feitas coletas trimestrais durante maio e novembro de 2021, no reservatório Epitácio Pessoa e em um trecho do rio Paraíba, ambos localizados no Estado da Paraíba. As amostras coletadas foram conservadas e levadas para identificação em laboratório, onde foram realizadas também as análises estatísticas através da abundância relativa das espécies, da diversidade de Shannon e de uma GLM, no programa RStudio. Os resultados mostraram que não houve diferença significativa na diversidade entre os dois ambientes (p>0,05). No entanto, a análise da abundância relativa revelou diferentes estruturas para os ambientes, onde, no reservatório, o grupo que se destacou foi o das cianobactérias, com 41,68%, apresentando relação negativa com a alcalinidade e os sólidos em suspensão. Enquanto no trecho do rio foram as clorofíceas que se destacaram, com 45,20% da abundância relativa, sendo positivamente relacionada à condutividade elétrica, pH, sólidos dissolvidos, sólidos suspensos totais, turbidez e temperatura da água e do ar, e negativamente relacionada com a alcalinidade, cloreto total e oxigênio. A prevalência de cianobactérias em um ambiente de abastecimento público deve servir como alerta aos gestores e pesquisadores, visto que a toxicidade desses organismos pode afetar as comunidades presentes nesse ecossistema e também a saúde e a economia das pessoas que utilizam desse recurso. Além disso, o aumento da frequência dos eventos de eutrofização, facilita o domínio de cianobactérias, gerando mais custos para restauração.

Aim The study analyzed the potential use of the phytoplankton functional groups as an environmental bioindicator in aquatic ecosystems of Brazilian semiarid region. Methods Using data collected over five years of a natural lagoon and two reservoirs, we evaluate the relationship between functional groups and environmental conditions through the multivariate approach. The Q index was applied to assess ecological status in these ecosystems. Results In Panati, the temporary and natural lagoon, the partial habitat desiccation and presence of macrophytes reflected in the less nutrients concentrations and phytoplankton composition, with high biomass of coccoids Chlorophyceae, diatoms and desmids (functional groups J, MP and N, respectively). Taperoá and Soledade reservoirs presented high cyanobacteria contribution, however the biomass and contribution of cyanobacteria in Taperoá (SN, S1) were lower than in Soledade. In this reservoir, cyanobacteria were more abundant, alternating in dominance (LO, M, LM, SN, S1). According to tendencies revealed by Redundancy Analysis (RDA), the main driving abiotic factors on the phytoplankton functional groups were pH, nutrients and light availability. As expected, phytoplankton composition directly influenced the Q index result, showing mostly bad to tolerable conditions in Soledade, medium to good in Taperoá and good to excellent in Panati. Conclusions The Q index was a good tool to assess the water quality and ecological status in aquatic ecosystems from the Brazilian semiarid region, reflecting the influence of natural control mechanisms on the harmful cyanobacteria blooms in temporary ecosystems. Resumo: Objetivo O estudo analisou o potencial uso dos grupos funcionais do fitoplâncton como bioindicador ambiental em ecossistemas aquáticos do semiárido brasileiro. Métodos Usando dados coletados de uma lagoa natural e dois reservatórios ao longo de cinco anos, avaliamos a relação entre grupos funcionais e condições ambientais por meio de uma abordagem multivariada. O índice Q foi aplicado para avaliar o estado ecológico desses ecossistemas. Resultados Em Panati, uma lagoa temporária e natural, a dessecação parcial do habitat e presença de macrófitas aquáticas refletiram nas menores concentrações de nutrientes e na composição do fitoplâncton, com alta biomassa de Chlorophyceae cocóides, diatomáceas e desmídias (grupos funcionais J, MP e N, respectivamente). Os reservatórios Taperoá e Soledade apresentaram alta contribuição de cianobactérias, no entanto a biomassa e a contribuição de cianobactérias em Taperoá (SN, S1) foram menores do que em Soledade. Nesse reservatório, as cianobactérias foram mais abundantes, alternando em dominância (LO, M, LM, SN, S1). De acordo com as tendências reveladas pela análise de redundância (RDA), os principais fatores abióticos atuantes sobre a estrutura dos grupos funcionais do fitoplâncton foram o pH, os nutrientes e a disponibilidade de luz. Como esperado, a composição do fitoplâncton influenciou diretamente o resultado do índice Q, mostrando condições ruins a toleráveis em Soledade, médias a boas em Taperoá e boas a excelentes em Panati. Conclusões O índice Q mostrou-se uma boa ferramenta para avaliar a qualidade da água e o estado ecológico de ecossistemas aquáticos do semiárido brasileiro, refletindo a influência de mecanismos naturais de controle sobre o florescimento de cianobactérias prejudiciais em ecossistemas temporários.

A new species of Parotocinclus is described from the Rio Mamanguape basin, in the State of Paraiba, north-eastern Brazil. The new species can be distinguished from all of its congeners, except for P. bahiensis, P. cesarpintoi, P. jumbo, P. nandae and P. spilosoma, by the presence of an abdomen covered by a few small and dispersed platelets (vs. an abdomen entirely covered by large plates in adult individuals or the absence of plates in that region). The new species differs from those mentioned above with respect to several features, such as an exposed pectoral girdle and supporting odontodes medially and laterally, the number of premaxillary and dentary teeth, odontodes covering only the lateral portion of the cleithrum and the absence of irregular golden lines on the head and body (colour in vivo). The new species was collected only in the upper and middle portions of the Rio Mamanguape basin, suggesting a geographic distribution restricted to the Caatinga biome.

Predictions of more frequent and intense toxic cyanobacterial blooms in the future arise due to the synergistic effects of eutrophication combined with climate change. Thus, the intensification of dry conditions in arid and semiarid areas promotes a reduction in the water level of aquatic ecosystems and favors the growth of cyanobacteria. Among these conditions, there is a lack of consensus on the role of nitrogen (N) or phosphorus (P) limitation, particularly when cyanobacterial communities are dominated by N-fixing taxa. The present study evaluated the effects of water volume reduction on cyanobacterial abundance and heterocyst production in semiarid tropical reservoirs during a period of prolonged drought. Physicochemical variables and the phytoplankton community were analyzed, and a structural equation model was built to identify the variables that explain the heterocystous cyanobacteria and heterocysts. The reduction in water volume increased the cyanobacterial biomass due to the increase in the biomass of heterocystous filamentous cyanobacteria associated with higher production of heterocysts. Heterocysts were correlated with an increase in the trophic status, low light availability and high salinity maintained under the lower volume conditions. In addition, contrary to expectations, heterocysts were not correlated with the N:P ratio, which suggests that in the tropics, N fixation does not necessarily occur when the N:P ratio is low, and N is limiting. These results indicate the potential for dominance of heterocystous filamentous cyanobacteria in future climate change scenarios, and therefore, we recommend that bloom mitigation strategies prioritize the reduction of N and P associated with the control of variables that favor heterocystous filamentous (i.e., light and salinity). We also recommend including cyanotoxin analysis in the relationship with lowering the water level to determine whether cell-bound toxin production and the associated risk to aquatic biota and humans are increased in the dry period.

The Floc and Sink technique promotes, through the application of coagulants and clays, the removal of phosphorus and algal biomass from the water column by flocculation and sedimentation. Although it is a promising technique for mitigating harmful cyanobacterial blooms, little is known about the impacts on other phytoplankton species as well as it is not known how species with mechanisms of resistance to sedimentation respond to the application of these products. In this study, a laboratory experiment was carried out with water from a eutrophic reservoir to assess the impact of applying aluminum-based coagulants, aluminum sulfate and polyaluminium chloride, and chitosan, alone and combined with lanthanum modified bentonite and natural bentonite on the phytoplankton community, in a functional approach based on morphology (Morphology-Based Functional Groups - MBFG, Kruk et al., 2010 and Reynolds et al., 2014), with an emphasis on the characteristics that provide resistance to sedimentation. We tested two hypotheses: phytoplankton species with adaptive mechanisms that provide buoyancy to cells are more resistant to the removal from the water column by coagulants and clays; and coagulants based on metals and modified clays are more efficient in sedimentation of microalgal cells compared to natural products, regardless of the presence of an adaptive mechanism of resistance to sedimentation. Our results showed that aluminum sulfate and polyaluminium chloride alone or combined with lanthanum modified bentonite and natural bentonite effectively sedimented the cells, regardless of the presence of buoyancy mechanisms. In contrast, the natural coagulant chitosan alone or combined with lanthanum modified bentonite and natural bentonite removed only those species that were small-celled or small colonial without specialized structures or with the presence of spines, arms and siliceous exoskeleton. In the case of species with aerotopes and flagella, the removal was not effective and still caused an increase in algal biomass due to the formation of suspended cell aggregates on the surface of the water column of the experimental units. Therefore, we concluded that the Floc and Sink technique has an impact on the phytoplankton community because it removes from the water column species that are not the target of coagulants and clays, but that are considered important sources of energy in freshwater trophic webs. This result differs according to the type of product used as well as it is related to the morphological adaptations that favor the buoyancy of cells in the water column. Species with aerotopes and flagella are more resistant to sedimentation and may make the use of products applied in the Floc and Sink technique unfeasible. Nevertheless, these results represent only an immediate effect of the technique on the phytoplankton community, thus requiring a longer time scale evaluation to determine the algae that can effectively recover water column. Therefore, we also emphasize that algae of nutritional value can recover over time and make the long-term application of the technique acceptable.

Evaluating the conservation of aquatic ecosystems, especially those which serve to supply, has been carried out using a variety of tools. However, the perception of water quality by the local community which lives in direct contact with water resources has not been considered with enough importance. This study analysed the relationship between the conservation status of reservoirs as perceived by the local community and their conservation status according to physical, chemical, and biological indicators. To do so, we calculated the Trophic State Index (TSI) of the reservoirs, the diversity and richness of benthic macroinvertebrate and we analysed the human influence in the riparian zone. Thus, we created the Community Conservation Perception Index (CCPI) to quantitatively associate the perception of the local community with environmental quality indicators (TSI, diversity, richness and anthropogenic influences in the riparian zone). We found that interviewee perception of reservoir conservation (using the CCPI) was related to trophic state, richness and diversity of benthic macroinvertebrate, and the presence of residences and agriculture in the riparian zone. It is necessary to consider the environmental perception of the local community as a relevant factor in management programmes and the conservation of ecosystems, even if artificial, as is the case with reservoirs. These communities can significantly contribute to maintaining the environmental quality through their performance in participatory management in projects such as: participating in the investigation of pollution in reservoirs, collecting parameters related to water quality, and community action in designing conservation strategies.

Construction of water diversions in drylands is boosted by increasing demands for freshwater often due to prolonged droughts. Even though these mega-enterprises result in benefits to society, it also poses a threat to freshwater biodiversity. In Northeastern Brazil, for instance, the São Francisco River Integration Project already supplies water for millions of people, but over time it will also favor the introductions of multiple aquatic species in the river basins of the Northeastern Caatinga and Coastal Drainages ecoregion. These introductions can cause unprecedented impacts in the native ichthyofauna, such as homogenization of freshwater faunas, transmission of pathogens and loss of native species. This study compares the composition and relative frequency of fish species from Poções reservoir using data obtained by gillnetting and trawling before and after the São Francisco diversion in the dry and rainy seasons, and reports the first detection of Moenkhausia costae introduction in the Paraíba do Norte basin, through the São Francisco River channel. Our results show some evidences that M. costae may become dominant and invasive in Poções reservoir. The introduction of M. costae adds a new component of disruption for these freshwaters and may pose a serious threat to the endemic ichthyofauna in lentic and lotic systems from the Paraíba do Norte basin. Resumo: Obras para transposição de rios em regiões secas do mundo têm sido impulsionadas pelo aumento da demanda por água doce, muitas vezes associadas às secas prolongadas que são intrínsecas a essas regiões. Embora tais megaempreendimentos possam trazer benefícios para a sociedade, também representam uma ameaça para a biodiversidade aquática. No Nordeste do Brasil, por exemplo, o Projeto de Integração do Rio São Francisco já fornece água para milhões de pessoas, mas com o tempo também contribuirá com a introdução de várias espécies aquáticas nas bacias hidrográficas da ecorregião Nordeste da Caatinga e Drenagem Costeira. Essas introduções podem causar impactos sem precedentes, tais como homogeneização da ictiofauna nativa, transmissão de patógenos e perda de espécies nativas. Este estudo compara a composição e frequência relativa de espécies de peixes do açude Poções usando dados coletados com redes de espera e de arrasto antes e depois da transposição do rio São Francisco, nos períodos seco e chuvoso, e relata o primeiro caso de introdução de Moenkhausia costae na Bacia do Rio Paraíba do Norte, através do canal do rio São Francisco. Nossos resultados mostram que M. costae poderá se tornar dominante e invasora no açude Poções. A introdução de M. costae adiciona um novo componente de perturbação para esse açude e pode representar uma séria ameaça à ictiofauna endêmica de sistemas lênticos e lóticos da bacia do rio Paraíba do Norte.

Melanoides tuberculata é uma espécie exótica de molusco já disseminada na maioria dos ambientes aquáticos do Brasil. O objetivo desse trabalho foi analisar se há relação das medidas alométricas e da biomassa de M. tuberculata com a gradiente de eutrofização em reservatórios. O estudo foi realizado em três reservatórios localizados na bacia do rio Paraíba, Nordeste do Brasil. O índice de estado trófico (IET) de Carlson, modificado por Toledo, foi aplicado para classificação trófica. Os resultados mostram a formação de três grupos entre os locais de amostragem com base no IET. Nos sites com maiores valores de IET foram encontrados os maiores tamanhos do molusco. Enquanto nos sites com níveis médios de eutrofização, os indivíduos tiveram comprimento intermediário. No grupo com a menor média de eutrofização, foram encontramos os menores comprimentos de M. tuberculata. A biomassa variou entre os grupos. As medidas alométricas estiveram relacionadas ao gradiente de eutrofização, especialmente quando se considerou, separadamente, as concentrações de fósforo e clorofila. Os resultados obtidos mostram que relações entre medidas alométricas de M. tuberculata e variações nas concentrações de fósforo e clorofila apresentam grande potencial para a avaliação da qualidade ambiental de reservatórios no semiárido do Brasil.

Parotocinclus haroldoi is separated from most of its congeners by having an abdomen covered by relatively large plates (vs. naked abdomen or with small plates). This species occurs in Parnaíba River basin with two other congeners, P. cabessadecuia and P. cearensis. Parotocinclus haroldoi is distinguished from P. cabessadecuia for having developed adipose fin (vs. rudimentary or absent adipose fin) and P. cearensis, for having abdomen covered by entirely plates (vs. almost naked abdomen with small sparse plates). Parotocinclus haroldoi is known from the Parnaíba river basin in the state of Piauí, Maranhão-Piauí.

Phosphorus (P) is the main nutrient responsible for the harmful effects caused by the enrichment of aquatic systems, and submerged macrophytes play an important role in this process, since they can both remove and release this nutrient in environmental compartments. The present study aimed to evaluate the influence of submerged macrophytes on P in the water, sediment, and water-sediment interface in a eutrophic reservoir in a semiarid region and to evaluate the relationship between the concentration of this nutrient in macrophyte tissue and that available in the different compartments. Were performed ten collection campaigns, in three reservoir locations: at the entrance of the Paraíba River; in the intermediate area between the river entrance and the dam and at the dam. We observed a difference in the P concentration inside and outside macrophyte banks, and this difference was determined by the abundance and intensity of macrophyte growth and decomposition. In sites with extensive vegetation banks and where decomposition was more intense, macrophytes released P to the water-sediment interface and sediment compartments. By contrast, in sites with smaller vegetation banks and where macrophytes did not show reduced abundance, P was removed from these compartments. The entry of new water originating from river water transfer was an important modifying factor of the physical and chemical characteristics and macrophyte abundance. The zone where the river enters the reservoir was the area most affected by the water transfer. The macrophyte decomposition in this zone resulted in the highest P concentration in the water-sediment interface and sediment compartments, which demonstrates the importance of macrophytes in the fertilization of water bodies and, consequently, in the eutrophication process. In turn, in the dam zone, where the macrophyte banks were more stable and without large variations in abundance, P was removed from the compartments. A relationship between P in macrophyte tissue and that available in the environment was observed, particularly at the water-sediment interface, indicating that this compartment was the main P source for these plants, which demonstrated that these plants store higher amounts of P in nutrient-rich sediment and water, functioning as an indicator of the nutritional status of a reservoir.

Tropical forests are characterized by high tree biomass that forms a dense canopy, thereby reducing the amount of light that reaches forest streams. Forest streams are likely to receive lar...

The functional diversity of phytoplankton communities was studied in two tropical estuaries subjected to anthropogenic pressure, despite one being environmentally protected. We applied functional diversity indices, analysed the dominant morphology traits and explored morphology-based functional groups. The less disturbed estuary showed slightly higher diversity and functional redundancy, during a wet season (on average 1.3 higher). Functional groups including nuisance species were more abundant in the heavily disturbed estuary. During a dry season, results for both systems were similar. Overall, abundance and functional diversity were higher in the upstream areas, associated with the river runoff containing freshwater species and essential nutrients for algae development. In both systems, diatoms were dominant (>75% of the community), however, the group included small and larger individuals, and freshwater to cosmopolitan species. This dominance and the change in traits were associated with sufficient nutrient supply, low light conditions, ressuspension and salinity changes, also associated with river runoff. Overall, the different functional diversity approaches enabled us to improve our understanding of the changes occurring in both systems.

Cyanobacteria harmful algal blooms (CyanoHABs) have become increasingly frequent and intense in public supply reservoirs as a result of eutrophication and global climate change. The semi-arid region of Brazil has a well documented history of CyanoHABs but the underlying factors that control the excessive proliferation of these organisms and the production of their bioactive secondary metabolites are not comprehensively understood. This study aimed to identify the environmental factors that explain the spatial and temporal variations in the abundance of cyanobacteria and the concentration of cyanotoxins (microcystins, saxitoxins, and cylindrospermopsin) in semi-arid reservoirs. The following hypotheses were tested: (a) the largest biovolumes of potential toxin producing cyanobacteria occur when cyanotoxin concentrations are highest; and (b) the environmental factors that explain variations in biovolume of cyanobacteria also explain changes in cyanotoxins concentrations. Samples were taken from four reservoirs located in the Northeast region of Brazil, over a three-month period (October 2016 and February and June 2017). Of the 24 species of cyanobacteria identified, 13 were potentially toxin-producing. Physicochemical variables such as water volume of the reservoir, water transparency, soluble reactive phosphorus, and total phosphorus explained the abundance of cyanobacteria and the levels of cyanotoxins. These results corroborate the hypothesis that similar physicochemical conditions influence the abundance and diversity of cyanobacteria and cyanotoxins. Cyanobacterial blooms composed of more than one potential toxin producing species were observed in the studied reservoirs, where potential microcystin-producing species were the most common. Microcystins and saxitoxins were detected in all the reservoirs studied, while cylindrospermopsin and the cyanobacterium Cylindrospermopsis raciborskii were simultaneously recorded in only one reservoir (Camalaú Reservoir). Cylindrospermopsin was only detected in a reservoir for the first time in the State of Paraíba. Canonical redundancy analysis showed that the cyanotoxins were related to potential toxin producing species. These results corroborate the proposed hypothesis that there is a correlation between cyanotoxins and the biomass of potential producers. Also, there were situations where cyanotoxins were detected without the presence of potential producers. These results demonstrate the need for reassessment of potential toxin producing species of cyanobacteria in semi-arid reservoirs. This may lead to the identification and characterization of novel producers of these bioactive secondary metabolites.

As atividades antrópicas são uma das principais causas da poluição dos ambientes aquáticos, pois favorece o fenômeno da eutrofização. Esse processo é caracterizado pelo crescimento elevado do fitoplâncton, considerado como bioindicador da qualidade ambiental desses ambientes. Este trabalho objetiva investigar a qualidade ambiental em um trecho urbano do rio Jaguaribe por meio da comunidade fitoplanctônica e das características químicas da água. As amostragens ocorreram durante o período chuvoso (Abril/2018) e seco (Julho/2018), em cinco pontos distribuídos ao longo do trecho urbanizado do rio. O fitoplâncton foi coletado através de uma rede coletora de plâncton. Adicionalmente, foram analisados os compostos nitrogenados e fosfatados da água. As maiores concentrações dos compostos nitrogenados e fosfatados ocorreram no período chuvoso, assim como a maior riqueza de espécies, resultado provavelmente influenciado pelo maior aporte de nutrientes decorrente da entrada de material alóctone no rio. As análises químicas revelaram, uma baixa qualidade das águas do rio Jaguaribe quando comparados com os padrões estabelecidos pelo CONAMA, o que foi corroborado pela presença de várias espécies de clorofíceas, cianofíceas e diatomáceas comuns em ambientes sob elevado nível de poluição. Dessa forma, faz-se necessário realizar um monitoramento periódico da qualidade da água devido à grande importância econômica, social e ecológica que o rio Jaguaribe possui para toda a região.

Geoengineering techniques have been used to control phosphorus and cyanobacteria in lakes promising greater and quicker chemical and ecological recovery. Techniques that use coagulants and clays to remove particulates and dissolved phosphorus from the water column have received great. In this study, bench-scale "flock & sink" assays were carried out to evaluate the efficiency of the coagulants aluminium sulphate (SUL), polyaluminium chloride (PAC) and chitosan (CHI), alone and combined with natural bentonite clays (BEN) and lanthanum-modified bentonite (LMB), to remove of phosphorus from a eutrophic reservoir in a semi-arid region of Brazil. In addition, the study seeks to assess the effects on the cyanobacteria density and the intra- and extracellular concentrations of cyanotoxins after the application of these geoengineering materials. The SUL and PAC coagulants effectively reduced the total phosphorus (TP), reactive soluble phosphorus (SRP), turbidity, chlorophyll-a, cyanobacteria density and intracellular microcystin, whereas CHI showed a low removal efficiency. Lanthanum-modified bentonite proved to be more effective than BEN; however, the application of the coagulants only was sufficient to successfully remove phosphorus and cyanobacteria from the water column. In addition, the efficiency of the "flock & sink" technique in cell removal varied among the cyanobacteria species. Small colonial species such as Aphanocapsa delicatissima, Merismopedia glauca and Merismopedia tenuissima were removed regardless of the treatment used, including those with CHI and BEN. As for the filamentous cyanobacteria, Cylindrospermopsis raciborskii, Geitlerinema amphibium, Planktothrix agardhii and Pseudanabaena catenata, removal was achieved only using PAC, SUL and LMB alone or when combined. The intracellular concentrations of saxitoxin and cylindrospermopsin and the extracellular fraction of these cyanotoxins and of microcystin were not influenced by the application of coagulants and clays. This indicates that cell lysis did not occur with the addition of the geoengineering materials. These results demonstrate that the "flock & sink" technique could be used for restoration of eutrophic waters.

Fatty acids are the main components of lipids and are necessary for the production and permeability of cell membranes, playing an essential role in the physiological responses of organisms. The biochemical composition of zooplankton might be used as bio-indicators of the trophic status of aquatic ecosystems. Aiming to fill the gap of knowledge in tropical estuaries, the main aim of this study was to test if the fatty acid profiles can reveal spatial and temporal shifts in the diet of copepods and therefore can be used as indicators of the trophic status of estuarine systems. We investigated the fatty acids composition of copepod species and their possible food sources along the salinity gradient of two tropical estuaries (Paraiba do Norte and Mamanguape estuaries, northeastern Brazil), during the rainy and dry seasons. We found clear seasonal differences regarding fatty acids composition and concentration in copepods, with maximal concentrations and diversity of total fatty acids during the rainy season. The copepods species were mainly carnivorous in the dry season and omnivorous in the rainy season and, in both estuaries, the diet of most copepods was dependent on food availability. The fatty acid profiles suggest that, in general, feeding patterns of zooplankton change spatially and temporally, reflecting the shifts in their food sources abundance (i.e., dominance among diatoms and flagellates, terrestrial detritus and small animals). We observed a residual proportion of terrestrial detritus and green algae in the diets and these items were only present in the dry season. Furthermore, the food sources in the Paraiba do Norte estuary, a system with high levels of anthropogenic disturbance, showed lower feeding quality, with lower essential fatty acids concentrations. Our study showed that fatty acid profiles can be used as ecological indicator to assess seasonal and spatial shifts in the trophic ecology of copepods in tropical estuaries and to distinguish systems with different levels of human impact in a fast and accurate way.

The aims of study were to 1) evaluate the productivity–diversity relationships (PDR) in reservoir phytoplankton communities in the semi-arid of northeastern Brazil on the local and regional scales; 2) determine the association between regional dissimilarity in species composition and regional mean productivity; 3) test the potential of productivity as well as physical and chemical factors of the water as descriptors of phytoplankton diversity using generalized linear models. Nutrient availability (total nitrogen and total phosphorus) and phytoplankton biomass were used as measures of productivity, whereas species richness as measure of diversity. Unimodal PDR was found when total phosphorus and biomass were considered as measure of productivity. Regional dissimilarity diminished with regional mean productivity. This finding may be attributed to the effect of eutrophication on diminishing the differences in the composition of species between compartments within each reservoir, leading to a loss of diversity in these ecosystems. Moreover, the analysis of the models demonstrated evidence that PDR may be influenced by environmental factors, such as electrical conductivity, total dissolved solids and pH in reservoirs located in semiarid regions of northeastern Brazil.

O presente estudo objetivou analisar a dinâmica de grupos funcionais do fitoplâncton e a variação do grau de trofia em reservatório do semiárido brasileiro durante estiagem prolongada. O estudo foi realizado no reservatório de Cordeiro, no município do Congo, Paraíba, com amostragens no período de junho a dezembro de 2015, com frequência trimestral, no ponto próximo ao barramento do reservatório. As espécies do fitoplâncton foram identificadas e quantificadas para obtenção da densidade, posteriormente as espécies foram classificadas de acordo com suas estratégias e grupos funcionais. O estado trófico foi determinado à partir do Índice do estado trófico para ambientes tropicais. O período de estudo foi caracterizado pela redução dos níveis de água acumulados no reservatório. A transparência do Secchi foi baixa, cujos valores foram inferiores a 1m. As concentrações de fósforo total durante o período de estudo foram elevadas (acima de 200 μg/L). As concentrações de clorofila a, tiveram valores mínimos de 8,17μg/L em julho de 2015, e máximos de 93,67 μg/L em outubro de 2015, com oscilações durante todo o período de estudo. O ambiente foi classificado como mesotrófico no mês de junho e eutrófico nos meses de outubro e dezembro. Foram identificadas dez espécies descritoras, agrupadas em quatro estratégias de vida (CS, C, R, e S) e 08 grupos funcionais (D, F, H1, N, P, X1 e Z). Os grupos funcionais refletiram as mudanças ambientais, sendo notória a presença de grupos típicos de lagos rasos meso-eutróficos. As espécies potencialmente tóxicas encontradas no estudo podem representar riscos à saúde das pessoas que utilizam essa água para consumo.

Atypical drought events have increasingly occurred in Brazil over the last years due to global climate changes. However, their consequences on aquatic biota in reservoirs are poorly known. We tested the hypothesis that macroinvertebrate communities are negatively affected by atypical drought events, given the sensitivity of many taxa to environmental changes. We predicted that: (a) there would be changes in limnological and sediment parameters between a regular year and an atypical year, (b) abundance and richness of the genera of Chironomidae and of exotic species would be higher due to the enhanced ability of these organisms to adapt to changes in the physical environment, and (c) community structure metrics (i. richness; ii. % richness; iii. abundance; iv. % abundance) would be affected by disturbance indices (i. Buffer Disturbance Index-BDI; ii. Local Disturbance Index-LDI; iii. Integrated Disturbance Index-IDI) in both years. The study was carried out in the reservoir of the Nova Ponte Hydroelectric Power Plant, state of Minas Gerais, comparing two sampling periods: a regular climatological year (2010) and an atypical drought year (2014). A total of 40 sampling sites were defined along the shore of the reservoir, and types of land use in the surrounding area of each site were measured, as well as physical habitat conditions, sediments, and benthic macroinvertebrate communities. Sampling was performed at these sites in the end of the rainy season in both years. The intensity of anthropogenic modifications was assessed at local scale and in the areas (buffers) surrounding the sampling sites using quantitative disturbance indices. There were striking differences in limnological parameters and sediment characteristics between sampling periods. Taxonomic richness was significantly lower in the drought year. As opposed to our predictions, richness and abundance of Chironomidae and exotic species did not increase with the atypical drought event. Besides, most community structure metrics showed a significant relationship with disturbance indices only during the regular climatological year, thus indicating that the large-scale effects of water stress may override the conditions of local habitats and the surrounding landscape. Therefore, in addition to a correct political-environmental management of water resources at local-scale, which includes maintaining the water quality and the riparian and landscape integrity, addressing large-scale climate issues is required for the maintenance of the ecological integrity of tropical reservoirs.

For mitigation of environmental problems generated by bad water resource management, the first step is to develop methods for effective diagnosis. The potential bioindicator, mainly in the benthic community, in the evaluation of water quality is the structure of the community, associated with magnitude of environmental impact. The aim of the present study was to evaluate the effectiveness of abundance biomass curves (ABC) as tools to estimate ecological quality in reservoirs in the Brazilian semi-arid region. Two reservoirs, Epitácio Pessoa and Argemiro de Figueiredo were selected. These reservoirs are located in the watershed of the Paraíba River, in Northeast Brazil. Sampling was done at 40 sites in the littoral region of each reservoir, during the periods of higher and lower water volume in the reservoirs. ABC for semi-arid region reservoirs showed disparate results for biological and environmental indicators, because they had a better relationship with momentary variables (physical and chemical parameters). This may be related to the high occurrence of exotic species, principally Corbicula largillierti, which has a high biomass, in association with a severe drought period. ABC must thus be used with parsimony and combined with other indicators, for an accurate and coherent characterization. Resumo Para mitigação de problemas ambientais gerados pela má gestão de recursos hídricos, o primeiro passo é o desenvolvimento metodologias de diagnósticos eficientes. O potencial bioindicador, principalmente da comunidade bentônica, na avaliação da qualidade da água deve-se aos aspectos estruturais dessa comunidade, associado com a magnitude de impactos ambientais. O objetivo do presente estudo foi avaliar a eficiência das curvas de biomassa e abundância (ABC) como ferramentas para estimar a qualidade ecológica em reservatórios na região do semi-árido brasileiro. Dois reservatórios, Epitácio Pessoa e Argemiro de Figueiredo foram selecionados. Estes reservatórios estão localizados na bacia do rio Paraíba, no nordeste do Brasil. As coletas foram realizadas em 40 locais na região litorânea de cada reservatório, durante os períodos de maior e menor volume de hídrico. As curvas ABC, quando plotadas em reservatórios do semiárido, apresentaram resultados diferentes aos indicadores biológicos e ambientais, tendo uma relação melhor com as variáveis momentâneas (parâmetros físicos e químicos). Isso pode estar relacionado à alta ocorrência de espécies exóticas, principalmente Corbicula largillierti, o que reflete uma elevada biomassa, combinada com um período severo de seca. O método ABC devem ser utilizadas com parcimônia e associada a outros indicadores, para uma caraterização coerente e precisa.

Macroinvertebrate communities have been widely used as a tool for assessing the environmental quality of freshwater ecosystems, whereas zooplankton communities have been to some extent neglected. However, the importance of using different indicators to achieve a more comprehensive framework of assessment regarding water quality has been recognized. This study compared estimates of species richness (number of species) and the Shannon–Wiener index for data on macroinvertebrate and zooplankton communities in tropical reservoirs and related them to their trophic state. The trop+hic classification was obtained by applying the Carlson index (1977) modified by Toledo et al. (1983), and the index of the Brazilian Society of the Environmental Technology Agency. The comparative response of the different indicators was analyzed using a series of bivariate correlations (Draftsman’s plot). The results illustrate that diversity measures, namely species richness, responded differently when related to the trophic classification of reservoirs, depending on the community considered. The species richness of zooplankton was positively related to hypereutrophic conditions, due to the higher number of rotifer species, including tolerant generalist species and at the same time, as a result of the exclusion of species from other groups, whereas for macroinvertebrates, species richness was negatively related to hypereutrophic conditions. Melanoides tuberculatus , which exhibits a high tolerance and competitive ability under such conditions, was the dominant species in macroinvertebrate communities, which excluded endemic species and reduced local richness and diversity. The same indicators applied to the zooplankton and macroinvertebrate communities might therefore provide contradictory responses regarding ecological quality assessment in tropical reservoirs, which suggest that zooplankton should be taken into account among the biological quality elements considered in the ecological quality assessment, management, and restoration of water bodies.

The scale of impact that the São Francisco River transposition project will have on the drainage basins ichthyofauna is still unclear, however, changes in the fish community diversity and abundance is probable. Surveys and registries of the fish fauna within key systems of the catchment basins are priority actions for the conservation of the aquatic diversity. This study conducted a taxonomic survey of the Epitácio Pessoa (Boqueirão municipality) and Argemiro de Figueiredo (Itatuba municipality), reservoirs ichthyofauna, both belonging to the Paraíba do Norte River basin, important socioeconomic and environmental systems for the transposition project. Monthly sampling was carried out between October/2014 to September/2015 in the upstream and downstream zones of the reservoirs. The specimens were collected using dip nets, drag nets, and sieves, and placed on ice in the field. Later in the laboratory, they were transferred to 10% formaldehyde and then preserved in 70% alcohol. A total of 2,328 specimens were collected representing five orders, 14 families, and 31 species in both systems. At the upstream zones 2057 specimens were collected representing 17 species, and at the downstream zones 271 specimens were collected representing 24 species. Of the 31 species recorded, 13 species are endemic to watersheds that drain rivers from the Brazilian semi-arid region, and seven species (Apareiodon davisi, Characidium bimaculatum, Hypostomus pusarum, Parotocinclus jumbo, P. spilosoma, Pimelodella enochi, and Prochilodus brevis) are endemic to the Mid-Northeastern Caatinga Ecoregion (MNCE). Among the latter, Parotocinclus spilosoma and Pimelodella enochi are endemic to the Paraíba do Norte River. Apareiodon davisi is classified as Endangered according to the current published Brazil’s official list of endangered species of fish and aquatic invertebrates. This pre-transposition ichthyofaunistic survey will serve as a basis for future post-transposition analyzes, considering this action will change the scope of the ecosystems diversity.

The aim of this study was to develop a statistical model to assess the environmental quality of reservoirs located in semi-arid region using metrics of anthropogenic disturbance, water quality variables, and benthic macroinvertebrate communities as indicators. The proposed model was applied to 60 sites located in three reservoirs in the Paraíba river basin, Brazilian semi-arid region. Collections were made in December 2011. In each site, we collected one sample of benthic macroinvertebrates and one water sample for the determination of physical and chemical parameters. Characterization of the landscape was made through application of 10 physical habitat protocols on each site for the collected information on disturbance and subsequent calculation of disturbance metrics. The results showed the formation of two groups: group 1, consisting of 16 minimally altered sites, and group 2, with 44 severely altered sites. The proposed statistical model was sensitive enough to detect changes. In the minimally altered group, the Chironomids Aedokritus and Fissimentum were dominant, indicating a higher environmental quality, while Coelotanypus and Chironomus were abundant in severely altered sites with lower environmental quality. The conservation and management of reservoirs in semi-arid regions should be intensified in view of the need to maintain the environmental quality of these ecosystems.

Hypersaline floodplains (sabkhas or saltflats) consist of the supratidal plains with low input of clastic sediments, high evaporation rates, and crustal salts. These environments are prone to periodical floodings and evaporite deposition, common in coastal areas with flat topography of arid regions, developing in response to two environmental conditions: deflation of surface sediments, or accumulation of sediments in a lake, or by a combination of both processes. This research developed a geochemical and textural characterization in soil samples collected in the estuarine floodplain (367.7 km2) of the Apodi-Mossoró River (Northeastern coast of Brazil), analyzing the results using multivariate statistics. The cluster and PCA analyses applied to the set of sampled sites enabled to identify two zones typical of the estuarine plain, as well as the major groups of parameters related, being one with the greater direct influence of tides (lower estuary) and another, upstream. This is a result of the a gradual accumulation in the soil (mainly the sodium), after the flood period in the spring tides, followed by a rapid water evaporation caused by high temperatures (>30°C) and constant winds.

This study assessed the functional diversity (FD) of copepod communities along the environmental gradient of two tropical estuaries with different intensities of human impact - the environmentally protected "Mamanguape" and the urbanised "Paraiba". Different trait-based approaches were used: functional groups identification and description, and FD indices estimation. The results showed similar functional groups and functional indices between the two estuaries with some variability attributed to seasonality. Copepods in each estuary seemed to perform similar functions. Overall, biomass was more evenly distributed among groups, and mean total biomass and FD indices were slightly higher in the Mamanguape. Nevertheless, both estuaries presented comparable FD, indicating that environmental filters may be the main driver of species coexistence within systems. Results also pointed towards anthropogenic disturbance, despite the protection status of the Mamanguape.

The hydrological periods drive the structure and organization of aquatic communities in semiarid regions. We hypothesize that a decrease of the precipitation during the dry period will favor the development of the periphytic algal community, leading to higher richness and density in this period. To test this hypothesis, we investigated the changes in the periphytic algal community structure in three shallow and eutrophic ecosystems of the Brazilian semiarid. The sampling was performed between 2007 and 2010 at two-mensal intervals. The sampling of periphytic algal was performed in aquatic macrophytes and rocks. The abiotic variables were analyzed simultaneously. Dominance in diatoms, cyanobacteria and chlorophytes, respectively, was observed in two periods. In the dry period, waters were alkaline and had high concentrations of nitrate and total phosphorus associated with the highest densities of Bacillariophyceae. In the rainy period the water was warmer, oxygenated and high concentrations of ammonia and soluble reactive phosphorus with diatoms remained dominant but with reduced density, while cyanobacteria and chlorophytes increased. Overall, periphytic algal community composition no responded to changes in the hydrological periods. However, the hydrological periods altered the dynamics of periphytic algal community, supported by the alternation of the most representative classes (diatoms and cyanobacteria) between the hydrologic periods. Our data suggest that the morphometric and chemical and physical characteristics of lentic aquatic ecosystems studied were more important in the dynamics of periphytic algal community than the hydrological periods and types of substrates. Resumo Os períodos hidrológicos impulsionam a estrutura e organização das comunidades aquáticas em regiões semiáridas. Nós hipotetizamos que uma diminuição da precipitação durante o período seco irá favorecer o desenvolvimento da comunidade de algas perifíticas, levando a uma maior riqueza e densidade nesse período. Para testar esta hipótese, nós investigamos as mudanças na estrutura da comunidade de algas perifíticas em três ecossistemas rasos e eutróficos do semiárido brasileiro. As amostragens foram realizadas entre 2007 e 2010 em intervalos de bimensais. A amostragem das algas perifíticas foi realizada em macrófitas aquáticas e rochas. As variáveis abióticas foram analisadas simultaneamente. A dominância de diatomáceas, cianobactérias e clorófitas, respectivamente, foi observada em todos os períodos. No período seco, as águas foram alcalinas com altas concentrações de nitrato e fósforo total associado às maiores densidades de Bacillariophyceae. Durante o período chuvoso as águas apresentaram-se mais quentes, oxigenadas e com altas concentrações de amônia e fósforo reativo solúvel. As diatomáceas permaneceram dominantes, mas com densidade reduzida, enquanto as cianobactérias e clorofíceas aumentaram. No geral, a composição da comunidade de algas perifíticas não respondeu as mudanças nos períodos hidrológicos. No entanto, os períodos hidrológicos alteraram a dinâmica da comunidade de algas perifíticas, apoiados pela alternância das classes mais representativas (diatomáceas e cianobactérias) entre os períodos hidrológicos. Nossos dados sugerem que as características morfométricas, químicas e físicas dos ecossistemas aquáticos lênticos estudados foram mais importantes na dinâmica da comunidade de algas perifíticas do que os períodos hidrológicos e tipos de substratos.

The introduction of exotic mollusk species has resulted in loss of biodiversity in semi-arid neotropical aquatic ecosystems. This study aims to relate the presence and density of Corbicula largillierti species to human disturbance, providing data for the conservation and management of aquatic ecosystems. Specimens were collected at Epitácio Pessoa reservoir in December 2011 and June 2012, presenting densities of 20.96 and 62.89 individuals per square meter, respectively. Anthropic disturbance metrics were calculated considering the presence, type and intensity of disturbance in littoral, riparian and flood zones. The occurrence of C. largillierti was mainly associated to the variables total phosphorus (261.05 ± 342.22 µg/L) and total nitrogen (440.79 ± 103.77 µg/L), near to tributaries. The occurrence of exotic mollusk species is evidence of the need for freshwater ecosystem conservation and management, particularly in reservoirs used for water supply. A introdução de espécies exóticas de moluscos resulta em perda de biodiversidade em ecossistemas aquáticos semiáridos neotropicais. Este estudo tem o objetivo de relacionar a presença e densidade da espécie Corbicula largillierti ao distúrbio humano, fornecendo dados para a conservação e manejo de ecossistemas aquáticos. Os espécimes foram coletados no reservatório Epitácio Pessoa em dezembro de 2011 e junho de 2012, com densidades de 20,96 e 62,89 indivíduos por metro quadrado, respectivamente. Métricas de perturbação antrópica foram calculadas considerando a presença, tipo e intensidade de perturbação nas zonas litorânea, ribeirinha e de inundação. A ocorrência de C. largillerti esteve associada ès variáveis fósforo total (261,05 ± 342,22 μg/L) e nitrogênio total (440,79 ± 103,77 μg/L), em locais próximos aos afluentes. A ocorrência de espécies exóticas de moluscos evidencia a necessidade de conservação e manejo de ecossistemas de água doce, principalmente em reservatórios utilizados para abastecimento de água.

Many species of bromeliads create an aquatic microcosm among their leaves. Besides their native aquatic fauna, these microcosms can be used by larvae of invasive mosquitoes like Aedes aegypti. We compared the mortality among A. aegypti larvae placed inside tanks of Aechmea fasciata bromeliads with larvae placed inside artificial microcosms and with microcosms with low pH (5.4), which simulate the acidic conditions found inside bromeliad tanks. A. aegypti larvae suffered a significantly higher mortality inside bromeliad tanks compared to larvae in control microcosms, but the mortality inside bromeliads did not differ statistically from that found in artificial microcosms simulating bromeliad acidic conditions. We concluded that bromeliad tanks tend to be a less suitable environment for the development of A. aegypti larvae than artificial containers due to the acidification generated by bromeliad physiology.

The aim of this study was to evaluate some parameters of water quality of semiarid reservoirs under different uses and occupation of the catchment’s soil. For this, the reservoirs Acauã and Boqueirão, belonging to the Paraíba do Norte river watershed and Middle and Upper course sub catchments, respectively, were studied. For this, water samples were collected in August, September and October 2016. From these samples, total and dissolved phosphorus, nitrate, nitrite, ammonia, chlorophyll, dissolved and suspended solids were analyzed. In addition, images of the Landsat 8 satellite were acquired for the calculation of the Normalized Difference Vegetation Index (NDVI), and for the supervised classification of the use and occupation of the sub catchments. Thus, it was observed that, in general, the Acauã reservoir presented values of phosphorus and nitrogen and solids larger than the Boqueirão reservoir, due to the greater urban area, even though it had a smaller total area of the basin. Both reservoirs presented low vegetation rates and high areas of sparse vegetation and exposed soil, increasing the propensity to soil erosion and the transport of nutrients from the basin to the reservoirs, making water quality worse or impossible.

O zooplâncton do reservatório de Mundaú, Pernambuco, nordeste do Brasil foi estudado quanto a variabilidade temporal (entre os horários e períodos seco chuvoso) e espacial (nas regiões pelágica e litorânea em diferentes profundidades) correlacionando-as com as variáveis ambientais e com o fitoplâncton. Vinte e três táxons infragenéricos e cinco subgenéricos de zooplâncton foram encontrados. De forma geral, Rotifera foi o grupo dominante em todo o estudo. O fitoplâncton foi dominado pelas cianobactérias. No período seco, as variáveis físicas certamente controlaram o desenvolvimento do zooplâncton, favorecendo o estabelecimento de elevadas densidades algais. No período chuvoso, a correlação do zooplâncton com os níveis de nutrientes do sistema na região pelágica provavelmente conduziu a uma competição de recursos entre o fitoplâncton e o zooplâncton, controlando as densidades algais. Zooplankton from Mundaú reservoir, State of Pernambuco, northeast Brazil was studied concerning temporal (hours and seasonal period) and spatial (pelagic and coastal regions in different depths) variabilities, correlating them to the environmental variables and the phytoplankton. Twenty-three infrageneric and five subgeneric zooplankton taxa were observed. On the whole, Rotifera was the dominant group during this study, especially influenced by the oxygen concentrations. Phytoplankton was dominated by Cyanobacteria. On the dry period, physical variables certainly controlled the zooplankton's development, allowing elevated algal densities. On the rainy period, zooplankton correlation with the system's nutrients levels on pelagic region probably conduced to a resources competition between phytoplankton and zooplankton, controlling algal densities.

ObjectiveThe objective of this study is to evaluate whether the distribution of structural attributes of rotifers in reservoirs in the semiarid region is more strongly influenced by abiotic or biotic environmental factors (density of cyanobacteria).MethodSampling occurred in two reservoirs in the Paraíba Basin, northeastern Brazil (Poções and Camalaú) during April and June 2012. Eight sampling points were distributed at two stations in each reservoir: the region near the entrance of the main tributary and region of the dam and collections were made in the limnetic and littoral zone in every season. To assess the abiotic influence and density of cyanobacteria in the distribution of the structural attributes of rotifers, environmental variables bivariate correlation was conducted in series.ResultsIn Poções reservoir, the distribution of rotifer biomass was negatively related to the density of cyanobacteria; among the environmental variables, chlorophyll-a and total nitrogen were negatively related to all of the tested structural attributes, while the concentrations of total phosphorus were strongly related to the abundance of rotifers. In the Camalaú reservoir, the biomass was a structural attribute with a stronger correlation to the density of cyanobacteria; between the environmental variables and Egeria densa, nitrate was negatively related to all of the attributes tested, while transparency was moderately related to the abundance, biomass and richness as well as Chara sp. with abundance.ConclusionsAssemblages of rotifers are more clearly related to environmental conditions, especially those indicative of trophic conditions, despite the density of cyanobacteria having been a factor that was positively related to the structural characteristics of rotifers and thus indicative of such structural assemblies. This can be used for analysis of local environmental condition factors. ObjetivoO objetivo deste trabalho é avaliar se a distribuição dos atributos estruturais de rotíferos em reservatórios no semiárido é mais fortemente influenciada por determinantes ambientais abióticos ou bióticos (densidade de cianobactérias).MétodoAs amostragens ocorreram em dois reservatórios na Bacia do Rio Paraíba, nordeste do Brasil (Poções e Camalaú) durante abril e junho de 2012. Oito pontos de amostragem foram distribuídos em duas estações em cada reservatório: região próxima a entrada do principal tributário e região de barragem e em cada estação foram realizadas coletas na zona litorânea e limnética. Para avaliação da influência das variáveis ambientais abióticas e da densidade de cianobactérias na distribuição dos atributos estruturais de rotíferos foi realizada análise de série bivariada de correlação.ResultadosNo reservatório Poções, a distribuição da biomassa de rotíferos esteve negativamente relacionada com a densidade de cianobactérias e entre as variáveis ambientais a clorofila-a e nitrogênio total foram negativamente relacionadas com todos os atributos estruturais testados enquanto que as concentrações de fósforo total estiveram fortemente relacionadas com a abundância dos rotíferos. No reservatório Camalaú, a biomassa foi o atributo estrutural com maior fator de correlação com a densidade de cianobactérias e dentre as variáveis ambientais, Egeria densa e nitrato foram relacionadas negativamente com todos os atributos testados, enquanto que a transparência esteve moderadamente relacionada com a abundância, biomassa e riqueza, assim como Chara sp. esteve com a abundância.ConclusõesAs assembleias de rotíferos é mais claramente relacionada a condições ambientais, especialmente as indicativas de condições tróficas, apesar da densidade de cianobactéria ter sido um fator que esteve positivamente relacionado com os atributos estruturais dos rotíferos e desta forma os indicativos estruturais dessas assembleias podem ser utilizados até mesmo como fatores de análise das condições ambientais locais.