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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.

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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.

The Curraleiro, also called Pé-Duro, is the only naturalized bovine breed of Northeastern Brazil. The breed originated via admixture of different Iberian breeds that were introduced during the sixteenth century and the subsequent natural adaptations to the semi-arid environment. The introduction of zebu bovine breeds during the twentieth century led to the replacement of the Curraleiro, which is now on the brink of extinction. With the aim of supporting the establishment of a conservation programme, the present study focused on assessing the management of the existing Curraleiro populations. Data on 2 366 head of cattle were obtained by interviewing 22 owners of Curraleiro herds. The number of animals in the herds varied from 4 to 384. The average herd size was 131.4 (standard deviation = 120.3). All animals were bred under extensive conditions, without any supplementary feed, and in 50 percent of all cases without any specialized technical assistance. Data indicated that breeders maintain the cattle not for economic reasons, but because of tradition. The Curraleiro was characterized by the breeders as being resistant to water stress and parasites. The animals can be bred without feed supplements on all kinds of native-grass pastures. These characteristics, in addition to its low production costs, could make the Curraleiro attractive, especially for low-income families. RésuméLe bétail Curraleiro, aussi appelé Pé-Duro, représente la seule race bovine naturalisée du Nord-est du Brésil. La race s'est formée suite au croisement de différentes races ibériques introduites au cours du seizième siècle et par l'adaptation naturelle à l'environnement semiaride. Les races zébuines introduites pendant le vingtième siècle ont remplacé la race Curraleiro qui se trouve actuellement au bord de l'extinction. Afin de soutenir l'établissement d'un programme de conservation, cette étude s'est concentrée sur la caractérisation de la conduite des élevages de race Curraleiro encore existants. Les données de 2 366 animaux ont été obtenues en enquêtant 22 propriétaires de troupeaux Curraleiro. Le nombre d'animaux par exploitation a varié de 4 à 384. La taille moyenne des troupeaux était de 131,4 avec un écart type de 120,3. Tous les animaux ont été élevés dans des conditions extensives, sans aucun complément alimentaire, et dans le 50 pour cent des cas sans aucune assistance technique spécialisée. Les données indiquent que les éleveurs maintiennent la race non pas pour des raisons économiques mais par tradition. Les éleveurs ont souligné que la race Curraleiro est résistante au manque d'eau et aux parasites. Les animaux peuvent être élevés, sans aucune supplémentation alimentaire, sur la base de n'importe quel pâturage natif. Ces caractéristiques, liées aux faibles coûts de production, pourraient rendre la race Curraleiro attirante, en particulier pour les familles à faibles revenus. Mots-clés: Bos taurus, bétail Curraleiro, race naturalisée, Nord-est du BrésilResumen El ganado Curraleiro, también llamado Pé-Duro, constituye la única ra...

The macrophytes play an important role in the regulation of biological and chemical processes in aquatic ecosystems, particularly in shallow lakes. They also play an important role in storage and nutrient cycling, serving as a source of organic matter to native environments. The aim of this study was to describe the kinetic aspects of the nutrients released during the anaerobic decomposition process of Egeria densa Planch and Chara braunii Gmnel macrophytes in waters with different trophic states. The study was conducted in vitro and under anaerobic conditions for determination of both particulate and dissolved fractions of nitrogenous, phosphorus and carbon, in predetermined days in oligotrophic and eutrophic water. Mathematical models were applied to describe the macrophytes decomposition process. Both species showed the same biphasic decay pattern of organic matter and carbon mineralization. The phosphorus, nitrogen and carbon released were high for both species, regardless of the trophic water state. The loss of mass was similar for both species and the nutrients concentration in the dam water did not represent a limiting factor for the mathematical model.