Isotopic profile and mercury concentration in fish of the lower portion of the rio Paraíba do Sul watershed, southeastern Brazil

Abstract

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,...

Effects of illegal gold mining on Hg concentrations in water, Pistia stratiotes, suspended particulate matter, and bottom sediments of two impacted rivers (Paraíba do Sul River and Muriaé River), Southeastern, Brazil

“…In the MR, there were also reports of an increase in garimpo activities since July 2021 (Folha de Italva, 2021b ; Jornal Terceira Via, 2021 ). Previous studies conducted in this drainage basin indicated high Hg concentrations in several fish species, especially demersal ones (up to 0.3 µg∙g −1 ), indicating the significant role of garimpo activities concerning Hg biota exposure (Azevedo et al, 2017 , 2018 ; Rocha et al, 2015 ).…”

Mercury Exposure and Toxicological Consequences in Fish and Fish‐Eating Wildlife from Anthropogenic Activity in Latin America

“…We compiled 763 unique fish species-location-date Hg means from 45 studies in Latin America, of which 17% lacked a corresponding mean length, weight, or age measurement. Martinelli et al 1988;Malm et al 1990;Reuther 1994;Castilhos et al 1998;dos Santos et al 2000;Leady and Gottgens 2001;Uryu et al 2001;Barbosa et al 2003;Dorea et al 2004;Bastos et al 2006Bastos et al , 2007Hylander et al 2006;Azevedo et al 2009;Kasper et al 2009;Beltran-Pedreros et al 2011;da Silva et al 2012da Silva et al , 2013de Souza Azevedo et al 2012;Bourdineaud et al 2015;Rocha et al 2015;Venturieri et al 2017Venturieri et al 1986Venturieri et al -1988Venturieri et al , 1990Venturieri et al -2005Venturieri et al , 2007…”

Nutrients Affecting the Characteristics of Food-Web Structure in Aquatic Ecosystem of Pearl River

“…Phytoplankton is an important primary producer in water ecosystems, and a main food source. In previous studies, the reported range of δ 13 C values of phytoplankton (Chrysophyta and Chlorophyta) was −37.2‰ to −23.6‰ [37][38][39][40][41][42]. These values are slightly different from that of zooplankton (−36.2‰), suggesting that phytoplankton are the main carbon source for zooplankton [29,39,43].…”

“…In previous studies, the reported range of δ 13 C values of phytoplankton (Chrysophyta and Chlorophyta) was −37.2‰ to −23.6‰ [37][38][39][40][41][42]. These values are slightly different from that of zooplankton (−36.2‰), suggesting that phytoplankton are the main carbon source for zooplankton [29,39,43]. There was study showed that the higher δ 13 C values of phytoplankton in eutrophic water (−28.45‰ to 23.63‰) are mainly due to the higher growth rate and abundance of Cyanophyta in warm, nitrogen-rich eutrophic water [44][45].…”