Before the Dam: A Fish-Mercury Contamination Baseline Survey at the Xingu River, Amazon Basin Before the Belo Monte Dam.

In the last decades, mega-diverse rivers worldwide (e.g., the Amazon and their tributaries) have experienced several human-driven transformations, although impact assessments oftentimes lack baseline data or reference values to better estimate observed disturbances. Herein, we assessed THg and δ15N in fish muscle tissue to determine biomagnification processes, also including seasonal assessments, concerning Hg in fish from the Belo Monte reservoir, located on the Xingu River, prior to its impoundment. A total of 312 samples from 19 fish species belonging to distinct feeding guilds were sampled. None presented THg concentrations above the threshold levels of 0.5 µg g-1 established by the World Health Organization. However, biomagnification was observed (R = 0.8; p < 0.001), also confirmed by a trophic magnification factor of 1.76 for the entire food web. The THg content in the water was less than 0.001 mg L-1 and only Hemiodus unimaculatus presented seasonal variations for THg. Therefore, at the time of this study, the Xingu River presented low Hg contamination levels in both water and target fish.

The consumption of shark meat in the Amazon region and its implications for human health and the marine ecosystem.

Here, we evaluated the levels of As, Hg, Pb, and Cd in shark meat sold along the Amazon Coast of Brazil and used nitrogen stable isotope values to determine trophic position and to assess element biomagnification. From market samples, a total of 13 species were identified via molecular analysis, including those listed as endangered and vulnerable by the IUCN Red List. Arsenic was present in significantly higher concentrations than all other elements, followed by Hg, with the highest mean concentrations recorded in M. higmani (As: 19.46 ± 8.79 µg/g ww) and C. acronotus (Hg: 1.12 ± 0.68 µg/g ww). Lead and Cd were recorded at much lower levels in all species. The EWI of individual elements were above PTWI for all species when considering Hg, seven species for inorganic arsenic (iAs), and one species for Pb. The weekly consumption of 10 species should be reduced to less than 416.39 g, which is equivalent to the daily estimated fish consumption rate in the region. The mean (±SD) δ15N values of species ranged from 10.7 ± 0.51‰ in M. higmani to 14.2 ± 0.59‰ in C. porosus, indicating feeding over >1 trophic level. Arsenic was negatively correlated with δ15N values, while Hg was positively correlated indicating biodilution and biomagnification, respectively. Our results indicate that the sale and consumption of shark meat will expose consumers to potentially harmful levels of iAs and Hg, as well as contributing to the population decline of species including those that are currently categorized as threatened.

The sea anemone Bunodosoma cangicum as a potential biomonitor for microplastics contamination on the Brazilian Amazon coast.

This study reports for the first time the ingestion of meso- (5.01-25 mm) and microplastics (1 µm-5 mm) by the sea anemone Bunodosoma cangicum, the most abundant actiniarian species on the Amazon coast. At three sites on the coast of Pará, Brazil, anemones were collected from beachrocks in the intertidal zone (30 at each site), measured (pedal disc diameter, mm) and weighed (wet weight, g). The contents of the gastrovascular cavity were extracted and analyzed under a stereoscope. The recovered plastic particles were characterized by Fourier Transform Infrared (FTIR) spectroscopy. Overall, 139 microplastic and 2 mesoplastic items were identified in 68 individuals (75.6%) among the 90 examined, with a mean of 1.6 (±1.5) items per individual. Plastic fibers comprised about 84% of the ingested plastics, followed by fragments (∼12%) and films (∼4%). Particle diameters ranged from 0.10 to 9.17 mm (1.57 ± 1.23 mm). A weak positive correlation was found between the weight of anemones and the number of plastic particles in the gastrovascular cavity (p = 0.03) and between the number of prey items and the number of plastic particles in the gastrovascular cavity (p < 0.01). The main polymers identified by FTIR analysis were polyethylene terephthalate (PET), polypropylene (PP), polyamide (PA), polyurethane (PU), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polystyrene (PS) and rayon. Sea anemones ingested significantly more plastic debris at the most urbanized and populous sampling sites. This study provides the first evidence of microplastics contamination of marine invertebrates from the Amazon coast. Abundant species such as B. cangicum have the potential to monitor the levels of plastic contamination in the region. Our results support this potential, as the species showed a high frequency of plastic ingestion and allowed detection of plastic contamination even in the best-preserved area where anemones were collected.

Redescription and range extension of the endangered Paiva's blenny Lupinoblennius paivai (Perciformes: Blenniidae).

The Paiva's blenny Lupinoblennius paivai is redescribed and its range redefined along the Brazilian coast. It differs from its congeners by the presence of three cephalic pores between the dorsal-fin base and lateral line, dorsal-fin elements XII, 12, anal-fin elements II, 16, pectoral-fin rays 14 and 10 + 20 vertebrae. It is here reported from Amazon estuaries (Marajó and Mosqueiro islands, Pará State), increasing its range by c. 3000 km. Lupinoblennius paivai is one of the few blenniid species able to tolerate low salinities. New data about its meristics and morphometrics are presented, as well as a new habitat type.

Evidence for habitat-driven segregation of an estuarine fish assemblage.

This study examined the spatio-temporal variability in fish assemblage structure and composition following monthly sampling (August 2006 to July 2007). Three estuarine zones (upper, middle and lower) of the unvegetated intertidal and subtidal channel habitats located in the Marapanim Estuary were investigated. In each of these zones, salinity, organic matter and sediment types were measured to assess any correlation between habitat types and the fish fauna. A total of 41 496 fishes, belonging to 76 species and 29 families, was recorded. Recurring changes in both species composition and trophic structure were attributed to seasonal variations, while habitat type played a more permanent role in modifying the structure of fish assemblages. Zooplanktivores (e.g. Lycengraulis grossidens) and herbivores (e.g. Cetengraulis edentulus) used the intertidal habitat almost exclusively and were associated with salinity and substratum composition (gravel, silt and mud). In contrast, benthophages (e.g. Cathorops spixii) and benthophage-ichthyophages (e.g. Cynoscion leiarchus) were primarily associated with the subtidal habitat throughout the estuary and were highly related to the presence of sandy substrata. This study highlighted the intricate roles that local factors (such as habitat connectivity) may have on the distribution of fishes at the assemblage level. As such, incorporating habitat sharing or segregation between species should be viewed as essential for any comparisons of estuaries over large geographic scales, and in particular for conservation planning and management measures.

Microgobius meeki as a potential bio-indicator of habitat disturbance in shallow estuarine areas: a useful tool for the assessment of estuarine quality.

The relationships between changes in habitat quality (disturbed and undisturbed sites) and the population parameters (density, size distribution, reproductive activity and diet) of a goby Microgobius meeki were investigated in a tropical estuary to assess its value as an indicator of anthropogenic changes, predominantly the effects of sedimentation and mangrove removal in shallow estuarine areas. Fish sampling surveys were conducted bimonthly between June 2009 and May 2010 over the entire estuarine gradient of the Paraguaçu River estuary, located on the central Brazilian coast. A predictive model was developed to assess the population changes of this species in 10 other tropical estuaries with different dimensions, basin features and distinct levels of anthropogenic disturbance. General linear models were used to relate the population structure of M. meeki to sediment type, habitat type resulting from mangrove conservation status, anthropogenic pressure and environmental characteristics such as salinity, dissolved oxygen concentrations and temperature. Sediment type and the presence of mangrove forests were the most effective predictors of local variability in the population structure of M. meeki. Individuals with mature gonads and high rates of feeding activity were associated predominantly with undisturbed habitats. Estuaries and estuarine sectors with high levels of sedimentation in shallow marginal areas, anthropogenic pressure from domestic and industrial effluents, and evidence of mangrove deforestation yielded the lowest capture rates of both juvenile and adult M. meeki. Based on these findings, M. meeki is identified as a potential indicator of the consequences of anthropogenic disturbance in transitional waters. A simple, but efficient collection protocol, in which overt signs of distress can be promptly observed is proposed. Testing the generality of this approach across different systems might prove useful in a broader conservation biology context.

Ontogenetic shifts in fishes between vegetated and unvegetated tidepools: assessing the effect of physical structure on fish habitat selection.

The aim of this study of tidepool fishes was analyse variation in their use of intertidal habitats (rocky shore, mangrove and salt marsh). Specimens were collected during wet and dry periods from 18 tidepools in the three habitats. A total of 7690 specimens, belonging to 19 families and 30 species, was captured. The fish assemblage in rocky shore pools was clearly distinct from that of vegetated habitats (mangrove and salt marshes). The rocky shore fauna was dominated by permanent resident species, whereas pools in mangrove and salt marsh habitats were inhabited primarily by opportunistic and transient species. Habitat segregation by ontogenetic stage (e.g. smaller individuals in mangroves, intermediate size classes in salt marsh and sub-adults/adults on rocky shores) indicates age-related migration in response to the physical structure of these habitats and to the natural history of each fish species. These findings are important for the development of effective conservation and management plans for intertidal fishes.

Mercury and methyl mercury in fishes from Bacajá River (Brazilian Amazon): evidence for bioaccumulation and biomagnification.

This study assessed total mercury (THg) and methyl mercury (MeHg) concentrations, bioaccumulation and biomagnification of THg through the food web in fishes consumed by indigenous communities of Bacajá River, the largest tributary of the right bank of Xingu River. In total, 496 fish (22 species) were sampled. Nine species had THg concentrations above the limit recommended by the World Health Organisation (0·5 µg g(-1) wet mass), and one exceeded the recommended level for Hg in predatory fishes by Brazilian law (1·0 µg g(-1) ). The average concentration of THg increased significantly with trophic guild (herbivorous to piscivorous) and trophic level, with higher accumulation in fishes with greater total length. Ninety-six per cent of all mercury was methylated. These results suggest that feeding habits determine THg concentrations in fishes and that Hg elimination rate is slow during growth, which allows greater accumulation. These findings show that fishes in the Bacajá River contain high concentrations of THg and MeHg.

Tometes kranponhah and Tometes ancylorhynchus (Characiformes: Serrasalmidae), two new phytophagous serrasalmids, and the first Tometes species described from the Brazilian Shield.

Two new species of Tometes from the Brazilian Shield rapids are described. Tometes kranponhah is endemic to the Xingu River basin, whereas Tometes ancylorhynchus occurs both in the Xingu and the Tocantins-Araguaia River basins. The two species are sympatric in the Xingu drainages and have many similarities in morphology and colouration. Major diagnostic differences are the dark pigmentation on the opercle of T. kranponhah and its distinct snout shape and arrangement of premaxillary teeth. In addition, T. kranponhah is a large fish that is abundant in the Xingu River, whereas T. ancylorhynchus is a medium-sized fish for which there are few records.

Effect of waterfalls and the flood pulse on the structure of fish assemblages of the middle Xingu River in the eastern Amazon basin.

The structure of fish assemblages in Neotropical rivers is influenced by a series of environmental, spatial and/or temporal factors, given that different species will occupy the habitats that present the most favourable conditions to their survival. The present study aims to identify the principal factors responsible for the structuring of the fish assemblages found in the middle Xingu River, examining the influence of environmental, spatial, and temporal factors, in addition to the presence of natural barriers (waterfalls). For this, data were collected every three months between July 2012 and April 2013, using gillnets of different sizes and meshes. In addition to biotic data, 17 environmental variables were measured. A total of 8,485 fish specimens were collected during the study, representing 188 species. Total dissolved solids, conductivity, total suspended matter, and dissolved oxygen concentrations were the variables that had the greatest influence on the characteristics of the fish fauna of the middle Xingu. Only the barriers and hydrological periods played a significant deterministic role, resulting in both longitudinal and lateral gradients. This emphasizes the role of the connectivity of the different habitats found within the study area in the structuring of its fish assemblages.

Length-weight relationships and condition factor of the eaglebeak pacu Ossubtus xinguense Jégu, 1992 (Characiformes, Serrasalmidae), an endangered species from Rio Xingu rapids, northern Brazil.

This study reports on the length-weight relationships and condition factor for the endangered rheophilic fish Ossubtus xinguense Jégu from Rio Xingu rapids. This species is threatened by construction of the third largest hydroelectric in the world, the Belo Monte dam close to the city of Altamira, northern Brazil. Specimens were collected in the dry season between July 2012 and September 2012. Male specimens have body length larger than females, atypical in serrasalmid fishes, and different length-weight relationships were found between adult and juvenile specimens. This study presents the first biological characteristics for O. xinguense.

Mercury concentration in different tissues of Podocnemis unifilis (Troschel, 1848) (Podocnemididae: Testudines) from the lower Xingu River - Amazonian, Brazil.

Studies using chelonians as biosentinels of environment quality or health risks associated with turtle consumption are very rare, especially in the Amazon basin. This study aims to measure Mercury levels (Hg) in muscle, liver, fat and blood of Podocnemis unifilis from the lower Xingu River, assessing the possible difference in concentration between sexes and also evaluating the potential bioaccumulation along different body sizes. Samples were collected during the dry season (October 2012) and Mercury (Hg) concentrations were analysed by Cold Vapor Atomic Absorption Spectrometry (CVAAS). A total of 29 specimens of P. unifilis of different sizes showed low levels lower than 0.2 mg/Kg). Higher Hg concentrations were found in the liver, and significant correlations between Hg concentrations in the different tissues were also detected. There was no difference between males and females and a negative correlation was found between Hg concentration and body size.

Population and biological parameters of selected fish species from the middle Xingu River, Amazon Basin.

This study estimates the main biological parameters, including growth rates, asymptotic length, mortality, consumption by biomass, biological yield, and biomass, for the most abundant fish species found on the middle Xingu River, prior to the construction of the Belo Monte Dam. The specimens collected in experimental catches were analysed with empirical equations and length-based FISAT methods. For the 63 fish species studied, high growth rates (K) and high natural mortality (M) were related to early sexual maturation and low longevity. The predominance of species with short life cycles and a reduced number of age classes, determines high rates of stock turnover, which indicates high productivity for fisheries, and a low risk of overfishing.

Effect of seasonal flooding cycle on litterfall production in alluvial rainforest on the middle Xingu River (Amazon basin, Brazil).

The assumption for this study was that litterfall in floodplain environments of the middle Xingu river follows a pattern of seasonal variation. According to this view, litterfall production (total and fractions) was estimated in four alluvial rainforest sites on the middle Xingu River over an annual cycle, and examined the effect of seasonal flooding cycle. The sites included two marginal flooded forests of insular lakes (Ilha Grande and Pimentel) and two flooded forests on the banks of the Xingu itself (Boa Esperança and Arroz Cru). Total litterfall correlated with rainfall and river levels, but whereas the leaf and fruit fractions followed this general pattern, the flower fraction presented an inverse pattern, peaking in the dry season. The litterfall patterns recorded in the present study were consistent with those recorded at other Amazonian sites, and in some other tropical ecosystems.

Population and biological parameters of selected fish species from the middle Xingu River, Amazon Basin / Parâmetros biológicos e populacionais de peixes do meio Rio Xingu, Bacia Amazônica

Abstract This study estimates the main biological parameters, including growth rates, asymptotic length, mortality, consumption by biomass, biological yield, and biomass, for the most abundant fish species found on the middle Xingu River, prior to the construction of the Belo Monte Dam. The specimens collected in experimental catches were analysed with empirical equations and length-based FISAT methods. For the 63 fish species studied, high growth rates (K) and high natural mortality (M) were related to early sexual maturation and low longevity. The predominance of species with short life cycles and a reduced number of age classes, determines high rates of stock turnover, which indicates high productivity for fisheries, and a low risk of overfishing.

Resumo Este estudo estima os parâmetros biológicos tais como taxas de crescimento corporal, comprimento assintótico, mortalidade, consumo por biomassa, produção biológica e biomassa, para 63 espécies no médio rio Xingu, antes da construção da hidrelétrica de Belo Monte. Os espécimes foram coletados por capturas experimentais e foram analisados com equações empíricas através do programa FISAT com base nos comprimentos corporais. Altas taxas de crescimento (K) e altas mortalidades naturais (M) foram relacionadas com uma maturação sexual precoce e baixa longevidade. O predomino de espécies com ciclos de vida curta e um reduzido número de classes etárias determinou altas taxas de renovação dos estoques, que indica alta produtividade para as pescarias e baixos riscos de sobrepesca.

Mercury concentration in different tissues of Podocnemis unifilis (Troschel, 1848) (Podocnemididae: Testudines) from the lower Xingu River – Amazonian, Brazil / Concentrações de mercúrio em diferentes tecidos de Podocnemis unifilis (Podocnemididae: Testudines) do baixo Rio Xingu – Amazônia, Brasil

Abstract Studies using chelonians as biosentinels of environment quality or health risks associated with turtle consumption are very rare, especially in the Amazon basin. This study aims to measure Mercury levels (Hg) in muscle, liver, fat and blood of Podocnemis unifilis from the lower Xingu River, assessing the possible difference in concentration between sexes and also evaluating the potential bioaccumulation along different body sizes. Samples were collected during the dry season (October 2012) and Mercury (Hg) concentrations were analysed by Cold Vapor Atomic Absorption Spectrometry (CVAAS). A total of 29 specimens of P. unifilis of different sizes showed low levels lower than 0.2 mg/Kg). Higher Hg concentrations were found in the liver, and significant correlations between Hg concentrations in the different tissues were also detected. There was no difference between males and females and a negative correlation was found between Hg concentration and body size.

Resumo Estudos utilizando quelônios como biosentinelas de qualidade ambiental ou de riscos à saúde associados ao consumo de tartarugas são raros, especialmente na bacia amazônica. Neste estudo foram medidos os níveis de mercúrio no músculo, fígado, gordura e sangue de Podocnemis unifilis do baixo Rio Xingu. Foram avaliadas as possíveis diferenças de concentração entre os sexos e também o potencial de bioacumulação ao longo de diferentes tamanhos corporais. A etapa de amostragem ocorreu durante o período seco (Outubro de 2012) e a quantificação de Mercúrio (Hg) foi realizada através de digestão ácida e análises por Espectrometria de Absorção Atômica com Vapor Frio (CVAAS). Um total de 29 amostras de Podocnemis unifilis, mesmo em diferentes tamanhos, mostraram concentrações de Hg menores que 0,2 mg/kg. As concentrações mais elevadas de Hg foram encontradas no fígado, e também foram detectadas correlações significativas entre as concentrações de Hg nos tecidos. Não foram observadas diferenças significativas entre machos e fêmeas, sendo registrada correlação negativa entre a concentração de Hg e o tamanho do corpo.

Length-weight relationships and condition factor of the eaglebeak pacu Ossubtus xinguense Jégu, 1992 (Characiformes, Serrasalmidae), an endangered species from Rio Xingu rapids, northern Brazil / Relações peso-comprimento e fator de condição do pacu-capivara Ossubtus xinguense Jégu, 1992 (Characiformes, Serrasalmidae), uma espécie ameaçada de extinção das corredeiras do Rio Xingu, norte do Brasil

Abstract This study reports on the length-weight relationships and condition factor for the endangered rheophilic fish Ossubtus xinguense Jégu from Rio Xingu rapids. This species is threatened by construction of the third largest hydroelectric in the world, the Belo Monte dam close to the city of Altamira, northern Brazil. Specimens were collected in the dry season between July 2012 and September 2012. Male specimens have body length larger than females, atypical in serrasalmid fishes, and different length-weight relationships were found between adult and juvenile specimens. This study presents the first biological characteristics for O. xinguense.

Resumo Este estudo relata as relações peso–comprimento e fator de condição para o peixe reofílico ameaçado de extinção Ossubtus xinguense Jégu. Esta espécie, endêmica das corredeiras do Rio Xingu, é ameaçada pela construção da terceira maior hidrelétrica do mundo, denominada Belo Monte localizada às proximidades da cidade de Altamira, norte do Brasil. Os espécimes foram coletados na estação seca do rio, entre julho e setembro de 2012. Espécimes machos apresentaram tamanho corporal maior que fêmeas, condição atípica entre os peixes serrasalmídeos, e diferentes relações peso–comprimento foram encontradas entre espécimes juvenis e adultos. Este estudo apresenta as primeiras características biológicas para O. xinguense.

Effect of waterfalls and the flood pulse on the structure of fish assemblages of the middle Xingu River in the eastern Amazon basin / Efeito das cachoeiras e do pulso de inundação na estrutura das assembleias de peixes do Médio Rio Xingu, Amazônia oriental

Abstract The structure of fish assemblages in Neotropical rivers is influenced by a series of environmental, spatial and/or temporal factors, given that different species will occupy the habitats that present the most favourable conditions to their survival. The present study aims to identify the principal factors responsible for the structuring of the fish assemblages found in the middle Xingu River, examining the influence of environmental, spatial, and temporal factors, in addition to the presence of natural barriers (waterfalls). For this, data were collected every three months between July 2012 and April 2013, using gillnets of different sizes and meshes. In addition to biotic data, 17 environmental variables were measured. A total of 8,485 fish specimens were collected during the study, representing 188 species. Total dissolved solids, conductivity, total suspended matter, and dissolved oxygen concentrations were the variables that had the greatest influence on the characteristics of the fish fauna of the middle Xingu. Only the barriers and hydrological periods played a significant deterministic role, resulting in both longitudinal and lateral gradients. This emphasizes the role of the connectivity of the different habitats found within the study area in the structuring of its fish assemblages.

Resumo A estrutura da ictiofauna em rios neotropicais é constantemente influenciada por fatores ambientais, espaciais e/ou temporais, uma vez que as espécies tendem a ocupar ambientes com condições favoráveis à sua sobrevivência. Dessa forma, esta pesquisa tem como objetivo responder qual o principal fator responsável pela estruturação das assembleias de peixes no Médio Rio Xingu, testando a influência dos fatores ambientais, espaciais e temporais, além da presença de barreiras naturais (cachoeiras). Os dados foram coletados, trimestralmente, entre os meses de julho de 2012 e abril de 2013, utilizando redes de emalhe de tamanhos de malha variados. Foram mensuradas 17 variáveis ambientais. Foram coletados 8.485 indivíduos distribuídos em 188 espécies. Observou-se que sólidos dissolvidos totais, condutividade, material em suspensão total e oxigênio dissolvido foram as variáveis que mais influenciaram a ictiofauna do médio Rio Xingu. Observou-se que apenas as barreiras naturais e os períodos hidrológicos foram determinantes, ocorrendo tanto variação longitudinal quanto lateral, ficando claro que a conectividade entre os diferentes trechos do médio rio Xingu é de suma importância na estruturação das assembleias de peixes.

Effect of seasonal flooding cycle on litterfall production in alluvial rainforest on the middle Xingu River (Amazon basin, Brazil) / Efeito da variação da inundação sazonal na produção de serrapilheira numa floresta aluvial do médio Rio Xingu (bacia do Amazonas, Brasil)

Abstract The assumption for this study was that litterfall in floodplain environments of the middle Xingu river follows a pattern of seasonal variation. According to this view, litterfall production (total and fractions) was estimated in four alluvial rainforest sites on the middle Xingu River over an annual cycle, and examined the effect of seasonal flooding cycle. The sites included two marginal flooded forests of insular lakes (Ilha Grande and Pimentel) and two flooded forests on the banks of the Xingu itself (Boa Esperança and Arroz Cru). Total litterfall correlated with rainfall and river levels, but whereas the leaf and fruit fractions followed this general pattern, the flower fraction presented an inverse pattern, peaking in the dry season. The litterfall patterns recorded in the present study were consistent with those recorded at other Amazonian sites, and in some other tropical ecosystems.

Resumo O pressuposto para este estudo foi que a produção de serrapilheira nos ambientes inundáveis do médio rio Xingu, segue um padrão de variação sazonal. Assim, se quantificou durante um ciclo anual a produção de serapilheira total e de suas frações, e se indagou a correlação entre o regime do nível do rio e a produção de serapilheira. Quatro ambientes de floresta ombrófila aluvial foram estudados: duas florestas inundáveis de lagoas insulares (Ilha Grande e Pimentel) e dois ambientes de floresta marginal no canal principal do rio Xingu (Boa Esperança e Arroz Cru). A produção de serapilheira total nos quatro ambientes mostrou um padrão sincrônico com a variação do nível do rio e com a inundação das áreas marginais. Por sua vez, foi evidente um aumento da produção de frutos durante a inundação local e de forma inversa uma maior produção de flores com o regime de seca. Os padrões registrados para os componentes de serapilheira do médio rio Xingu, confirmam os achados para outros ambientes amazônicos e tropicais.