RESUMO
This study analyzes the influences of environmental variables on the weight-length relationship of the penaeid shrimp Xiphopenaeus kroyeri during nine consecutive years (2005 to 2013) in northern Rio de Janeiro State. The main questions raised are: i) Does species relative growth vary along time? and ii) How are the environmental variables sea surface temperature, salinity, chlorophyll-a and/or organic matter related to the relative growth? For males, the long-term mean of the allometric coefficient stayed <3 (immature: 2.49; mature: 2.91), whereas for females they were >3 (immature: 3.08; mature: 3.10). The sine-consine models highlighted the wave T period in which the allometric coefficient values complete one cycle of increase-decrease: 4.72 years and 14.72 years for immatures female and male, respectively; and 9.08 years and 9.98 years for matures male and females, respectively. The relative growth behavior varies in a predictable time scale; however, none of the environmental variables strongly supported the variation. Changes in the relative growth behavior are probably drive by intrinsic mechanisms to maintain the population locally.
Assuntos
Penaeidae , Animais , Brasil , Feminino , Masculino , Salinidade , TemperaturaRESUMO
Food is the main source of toxic metals like mercury (Hg) and cadmium (Cd) to humans. This study evaluated the accumulation and translocation of Cd and Hg in a soil-plant system in four tomato plantations and assessed the risk associated with ingestion of these metals. Ten soil samples (rhizosphere) and 10 samples of plant tissues (leaf, ripe fruit, green fruit, and roots) were collected in each plantation. Spatial variation in Cd and Hg concentrations was negligible. The Cd level in rhizosphere was lower in comparison with that of plant tissues. Hg levels in rhizosphere were similar to roots and higher than the value observed in aerial parts of plants. The Cd bioconcentration factor was approximately five times higher compared to that of Hg. Approximately 93% and 48.6% of Cd and Hg accumulated in roots reached aerial parts, respectively. Our results indicate that tomato readily absorbs Cd accumulated in soil, translocating it to aerial parts. Comparatively, the absorption of Hg is not efficient. Levels of Cd in tomatoes were over 17 times higher than the maximum residual levels in 57.5% of ripe fruits and in 27.5% of green tomatoes.
Assuntos
Cádmio/metabolismo , Monitoramento Ambiental , Mercúrio/metabolismo , Poluentes do Solo/metabolismo , Solanum lycopersicum/metabolismo , Transporte Biológico , Brasil , Exposição Ambiental , Frutas/crescimento & desenvolvimento , Frutas/metabolismo , Humanos , Ferro/metabolismo , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Medição de Risco , Zinco/metabolismoRESUMO
Damming rivers to generate electricity creates a lentic environment that favors methylmercury (MeHg) formation. Reservoirs in the Amazon are critical environments for MeHg formation, considering its old soils and the use of Hg in gold mining in the region. The objective of this study was to evaluate MeHg accumulation in three environmental compartments (aquatic macrophytes, suspended particulate matter (SPM) and sediment) of the Samuel reservoir (Western Amazon, Brazil), during the low water, ebb and high water hydrological periods, characterizing the dry season, the end of the rainy season and the rainy season, respectively. MeHg concentrations were determined through GC-AFS. The aquatic macrophytes presented higher %MeHg in their roots (up to 12%) compared to their other tissues. This ratio was 1.7 and 5.9 times higher than those observed for SPM and the sediment, but MeHg concentrations were the lowest (0.5-4.5â¯ngâ¯g-1) among the three environmental compartments. Contrary, the highest MeHg concentration was observed in SPM (104â¯ngâ¯g-1) during the low water period. The MeHg concentration in the sediment profile decreased with increasing depth (0.93-0.48â¯ngâ¯g-1) and with decreasing organic matter lability (increasing C:N ratio). In the SPM, on the other hand, MeHg concentration showed a positive association with increasing C:N ratio. We conclude that MeHg dynamics in the SPM are associated with the hydrological periods, with peaks during the low water period. The organic matter lability of the sediments is more limiting to the production of MeHg than the total Hg concentrations.
Assuntos
Monitoramento Ambiental/métodos , Sedimentos Geológicos/análise , Compostos de Metilmercúrio/análise , Material Particulado/análise , Poluentes Químicos da Água/análise , Brasil , Centrais Elétricas , RiosRESUMO
The aim of this study was to evaluate the isotopic profile and mercury (Hg) concentrations in fish (carnivores, omnivores and detritivores) in the lower portion of the rio Paraíba do Sul watershed, southeastern Brazil. Carbon (δ13C) isotopic analyses revealed that pelagic and benthonic sources are part of the feeding of the fish from the different guilds (-14.0 to -24.8 ). The benthic sources are usually enriched in δ13C (-16.9, from watershed runoff) compared to pelagic sources because the phytoplankton, important primary producer that supports several pelagic chains, has δ13C signature lighter (-23.9). The nitrogen (δ15N) isotopic signatures indicated that most guilds were at the same trophic position (10.0 to 15.5 ), except for pelagic omnivorous fish, which had a lower trophic position. Niche overlap was observed among pelagic and demersal carnivorous fish, demersal omnivorous fish, and demersal detritivorous fish. The lower isotopic niche breadth of pelagic carnivorous fish reveals the specialized resource use by this guild. Hg concentrations (ng g-1 dry weight) differed significantly between demersal carnivorous fish (185.3 dry weight; 27.8 wet weight) and demersal omnivorous fish (277.9 dry weight; 41.7 wet weight) and between pelagic omnivorous fish (197.2 dry weight; 29.6 wet weight) and demersal omnivorous fish due to (1) differences in food sources: guilds that fed on bottom resources were more affected by contamination because the sediment is an important Hg accumulator in the study area, and (2) because of its trophic positions. Considering that the fish consumed prey of similar trophic positions, the guilds did not show a well-defined food hierarchy. Therefore, in this study, there was no clear relationship between Hg and δ15N.
O objetivo deste estudo foi avaliar o perfil isotópico e as concentrações de mercúrio (Hg) em peixes (carnívoros, onívoros e detritívoros) na bacia inferior do rio Paraíba do Sul, sudeste do Brasil. As análises isotópicas de carbono (δ13C) revelaram participação de fontes pelágica e bentônica na alimentação dos peixes das diferentes guildas (-14,0 a -24,8 ). As fontes bentônicas são usualmente mais enriquecidas em δ13C (-16,9, derivado do escoamento superficial da bacia de drenagem) comparadas às fontes pelágicas pois, o fitoplâncton, importante produtor primário que suporta inúmeras cadeias pelágicas, tem assinatura de δ13C mais leve (-23,9). As assinaturas isotópicas de nitrogênio (δ15N) indicaram que a maioria das guildas estava no mesmo nível trófico (10,0 a 15,5 ), exceto os peixes onívoros pelágicos cuja posição trófica foi inferior. Observou-se sobreposição de nicho entre peixes carnívoros pelágicos e demersais, onívoros demersais, e detritívoros demersais. A menor amplitude de nicho isotópico dos peixes carnívoros pelágicos revela o uso de recursos especializados por esta guilda. A concentração de Hg (ng g-1 peso seco) diferiu significativamente entre peixes carnívoros demersais (185,3 peso seco; 27,8 peso úmido) e onívoros demersais (277,9 peso seco; 41,7 peso úmido), e entre peixes onívoros pelágicos (197,2 peso seco; 29,6 peso úmido) e onívoros demersais devido a (1) diferenças nas fontes alimentares: guildas que utilizaram recursos de fundo foram mais afetadas pela contaminação pois o sedimento é um importante acumulador de Hg na área de estudo, e (2) por causa das suas posições tróficas. Tendo em vista que os peixes consumiram presas com níveis tróficos semelhantes, as guildas não apresentaram uma hierarquia alimentar definida. Desse modo, no presente estudo não se verificou uma relação clara entre Hg e δ15N.
Assuntos
Animais , Isótopos de Mercúrio/análise , Isótopos de Mercúrio/isolamento & purificação , Peixes/crescimento & desenvolvimento , Peixes/fisiologiaRESUMO
The aim of this study was to evaluate the isotopic profile and mercury (Hg) concentrations in fish (carnivores, omnivores and detritivores) in the lower portion of the rio Paraíba do Sul watershed, southeastern Brazil. Carbon (δ13C) isotopic analyses revealed that pelagic and benthonic sources are part of the feeding of the fish from the different guilds (-14.0 to -24.8 ). The benthic sources are usually enriched in δ13C (-16.9, from watershed runoff) compared to pelagic sources because the phytoplankton, important primary producer that supports several pelagic chains, has δ13C signature lighter (-23.9). The nitrogen (δ15N) isotopic signatures indicated that most guilds were at the same trophic position (10.0 to 15.5 ), except for pelagic omnivorous fish, which had a lower trophic position. Niche overlap was observed among pelagic and demersal carnivorous fish, demersal omnivorous fish, and demersal detritivorous fish. The lower isotopic niche breadth of pelagic carnivorous fish reveals the specialized resource use by this guild. Hg concentrations (ng g-1 dry weight) differed significantly between demersal carnivorous fish (185.3 dry weight; 27.8 wet weight) and demersal omnivorous fish (277.9 dry weight; 41.7 wet weight) and between pelagic omnivorous fish (197.2 dry weight; 29.6 wet weight) and demersal omnivorous fish due to (1) differences in food sources: guilds that fed on bottom resources were more affected by contamination because the sediment is an important Hg accumulator in the study area, and (2) because of its trophic positions. Considering that the fish consumed prey of similar trophic positions, the guilds did not show a well-defined food hierarchy. Therefore, in this study, there was no clear relationship between Hg and δ15N.(AU)
O objetivo deste estudo foi avaliar o perfil isotópico e as concentrações de mercúrio (Hg) em peixes (carnívoros, onívoros e detritívoros) na bacia inferior do rio Paraíba do Sul, sudeste do Brasil. As análises isotópicas de carbono (δ13C) revelaram participação de fontes pelágica e bentônica na alimentação dos peixes das diferentes guildas (-14,0 a -24,8 ). As fontes bentônicas são usualmente mais enriquecidas em δ13C (-16,9, derivado do escoamento superficial da bacia de drenagem) comparadas às fontes pelágicas pois, o fitoplâncton, importante produtor primário que suporta inúmeras cadeias pelágicas, tem assinatura de δ13C mais leve (-23,9). As assinaturas isotópicas de nitrogênio (δ15N) indicaram que a maioria das guildas estava no mesmo nível trófico (10,0 a 15,5 ), exceto os peixes onívoros pelágicos cuja posição trófica foi inferior. Observou-se sobreposição de nicho entre peixes carnívoros pelágicos e demersais, onívoros demersais, e detritívoros demersais. A menor amplitude de nicho isotópico dos peixes carnívoros pelágicos revela o uso de recursos especializados por esta guilda. A concentração de Hg (ng g-1 peso seco) diferiu significativamente entre peixes carnívoros demersais (185,3 peso seco; 27,8 peso úmido) e onívoros demersais (277,9 peso seco; 41,7 peso úmido), e entre peixes onívoros pelágicos (197,2 peso seco; 29,6 peso úmido) e onívoros demersais devido a (1) diferenças nas fontes alimentares: guildas que utilizaram recursos de fundo foram mais afetadas pela contaminação pois o sedimento é um importante acumulador de Hg na área de estudo, e (2) por causa das suas posições tróficas. Tendo em vista que os peixes consumiram presas com níveis tróficos semelhantes, as guildas não apresentaram uma hierarquia alimentar definida. Desse modo, no presente estudo não se verificou uma relação clara entre Hg e δ15N.(AU)