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Cite as: Gomes, M.A.C. et al. Salinity effects on photosynthetic pigments, proline, biomass and nitric oxide in Salvinia auriculata Aubl. Acta Limnologica Brasiliensia, 2017, vol. 29, e9. Abstract: Aims: Effects of salt stress on the physiology of Salvinia auriculata were investigated. Method: Plants were supplemented with 0, 50, 100 and 150 mmol L -1 NaCl and incubated for 5 days. NO content was evaluated after 2 hours and 5 days. Photosynthetic pigments, proline and nutrients were analyzed after 5 days. Major Results: Higher chlorophyll a content was observed in plants treated with 50 mmol L -1 , decreasing in higher NaCl concentrations, while chorophyll b content decreased with increasing NaCl concentrations. Exposure to 50 mmol L -1 NaCl increased biomass, while higher concentrations caused loss of biomass. Ca, K and Mg decreased with increasing NaCl concentrations, and the Na/K ratio was significantly increased at 150 mmol L -1 NaCl. Proline increased significantly at 150 mmol L -1 . Extracellular NO content increased after 2 hours, with significantly higher NO concentrations in roots observed at 50 mmol L -1 . Decreases in NO content were observed after 5 days. Conclusions: The results indicate that moderate salinity induces NO production earlier during incubation, probably associated to signaling for the production of compounds that assist in stress tolerance. At higher concentrations, this tolerance is reduced. This allows for further understanding of the physiological and biochemical mechanisms associated with the adaptation of this macrophyte to saline conditions, which, in turn, affect this species ecology and distribution in coastal areas.Keywords: Salvinia auriculata; salinity stress; nitric oxide; clorophyll; NaCl; macrophyte.Resumo: Objetivos: Efeitos do estresse salino sobre a fisiologia de Salvinia auriculata foram investigados. Metodologia: As plantas foram expostas a 0, 50, 100 e 150 mmol de NaCl L -1 e incubadas durante 5 dias. O conteúdo de NO foi avaliado após 2 horas e 5 dias. Pigmentos fotossintéticos, prolina e nutrientes foram analisados após 5 dias. Resultados Principais: Observou-se maior teor de clorofila a em plantas tratadas com 50 mmol L -1

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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 (δ 13 C) 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 δ 13 C (-16.9‰, from watershed runoff) compared to pelagic sources because the phytoplankton, important primary producer that supports several pelagic chains, has δ 13 C signature lighter (-23.9‰). The nitrogen (δ 15 N) 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 δ 15 N.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 (δ 13 C) 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 δ 13 C (-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 δ 13 C mais leve (-23,9‰). As assinaturas isotópicas de nitrogênio (δ 15 N) 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,...