Floodplain systems are widespread in the Amazon and several studies have evaluated mercury biogeochemistry in these systems. The Amazon region can be considered a “hotspot” for the study of mercury (Hg), due to the naturally high concentration of the pollutant in its old soils and the anthropogenic emissions from small-scale gold mining activities. The periodic flooding influences the availability and distribution of Hg contamination. Therefore, it is possible that flooding can influence accumulation of Hg in fish. The aim of this study was to evaluate total Hg (THg) concentration in four seasons (rising water, high water, falling water and low water) in six fish guilds in a lentic part of a floodplain system (Puruzinho Lake). We hypothesized that fish guilds would show different seasonal patterns of THg concentration variation. A total of 2016 fish specimens were sampled over the four seasons. Two-way ANOVA indicated an interaction between guilds and seasonality (F = 7.3; p < 0.001), suggesting different seasonal patterns of THg concentration variation among the guilds. Two major patterns were identified. Herbivorous, detritivorous, carnivorous and piscivorous fish guilds showed higher concentrations during the rising and low water seasons, while planktivorous and omnivorous guilds showed lower THg levels during the low water season. There were no significant differences in THg levels between the early and late periods of each season.

洪泛区系统在亚马逊地区很普遍，并且一些研究评估了这些系统中的汞生物地球化学。亚马逊地区可被视为研究汞（Hg）的“热点”，这是由于其旧土壤中污染物的自然浓度很高以及小规模金矿开采活动造成的人为排放。周期性的洪水影响汞污染的可用性和分布。因此，洪水可能会影响鱼类体内汞的积累。本研究的目的是评估洪泛区系统（Puruzinho湖）的一个透镜体部分的六个鱼类行会在四个季节（上升水，高水，下降水和低水）中的总Hg（THg）浓度。我们假设鱼行会表现出不同的THg浓度变化的季节性模式。在这四个季节中总共采样了2016个鱼标本。双向方差分析表明行会与季节性之间存在相互作用（F = 7.3；p  <0.001），表明行会中THg浓度变化的不同季节模式。确定了两种主要模式。草食性，有害性，肉食性和食肉性鱼类行会在上升和淡水季节显示较高的浓度，而浮游性和杂食性公会在淡水季节显示较低的THg水平。在每个季节的早期和晚期之间，THg水平没有显着差异。