Lammi Biological Station, University of Helsinki, Pääjärventie 320, FI-16900, Lammi, Finland.
Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35 (YA), FI-40014, Jyväskylä, Finland.
Environ Res. 2023 Aug 15;231(Pt 2):116187. doi: 10.1016/j.envres.2023.116187. Epub 2023 May 22.
Boreal lakes demonstrate pronounced seasonality, where the warm open-water season and subsequent cold and ice-covered season dominate natural cycles. While fish muscle total mercury concentration (mg/kg) [THg] is well documented in open-water summer months, there is limited knowledge on the ice-covered winter and spring mercury dynamics in fish from various foraging and thermal guilds. This year-round study tested how seasonality influences [THg] and its bioaccumulation in three percids, perch (Perca fluviatilis), pikeperch (Sander lucioperca), ruffe (Gymnocephalus cernua), and three cyprinids, roach (Rutilus rutilus), bleak (Alburnus alburnus), and bream (Abramis brama) in deep boreal mesotrophic Lake Pääjärvi, southern Finland. Fish were sampled and [THg] was quantified in the dorsal muscle during four seasons in this humic lake. Bioaccumulation regression slopes (mean ± STD, 0.039 ± 0.030, range 0.013-0.114) between [THg] and fish length were steepest during and after spawning and shallowest during autumn and winter for all species. Fish [THg] was significantly higher in the winter-spring than summer-autumn in all percids, however, not in cyprinids. The lowest [THg] was observed in summer and autumn, likely due to recovery from spring spawning, somatic growth and lipid accumulation. Fish [THg] was best described by multiple regression models (R: 52-76%) which included total length and varying combinations of seasonally changing environmental (water temperature, total carbon, total nitrogen, and oxygen saturation) and biotic factors (gonadosomatic index, and sex) in all species. The seasonal variation in [THg] and bioaccumulation slopes across multiple species suggests a need for standardized sampling seasons in long-term monitoring to avoid any seasonality bias. From the fisheries and fish consumption perspective in seasonally ice-covered lakes, monitoring of both winter-spring and summer-autumn would improve knowledge of [THg] variation in fish muscle.
北方湖泊表现出明显的季节性，温暖的开阔水域季节和随后的寒冷及冰封季节主导着自然循环。虽然鱼类肌肉总汞浓度（mg/kg）[THg]在开阔水域夏季得到了充分记录，但对于来自不同觅食和热群的鱼类在冰封冬季和春季的汞动态知之甚少。本全年研究测试了季节性如何影响三种鲈形目鱼类（鲈鱼、梭鲈、彩鲫）和三种鲤科鱼类（欧椴、丁鱥、鲤鱼）的[THg]及其生物累积，这些鱼类样本取自芬兰南部深营养中型富营养化湖泊 Pääjärvi 的冰面下。在这个腐殖质湖泊中，在四个季节采集鱼类样本并在背部肌肉中定量[THg]。在所有物种中，[THg]与鱼体长之间的生物累积回归斜率（平均值±标准差，0.039±0.030，范围 0.013-0.114）在产卵期间和之后最为陡峭，而在秋季和冬季最为平缓。所有的鲈鱼，其冬季-春季的[THg]显著高于夏季-秋季，但在鲤鱼中则不然。在所有的鱼类中，[THg]最低的是在夏季和秋季，这可能是由于春季产卵后的恢复、身体生长和脂肪积累。[THg]最好用多元回归模型（R：52-76%）来描述，这些模型包括总长度和季节变化的环境（水温、总碳、总氮和氧气饱和度）和生物因素（性腺体指数和性别）的各种组合。在所有物种中，[THg]和生物累积斜率的季节性变化表明，在长期监测中需要标准化的采样季节，以避免任何季节性偏差。从季节性冰封湖泊的渔业和鱼类消费角度来看，监测冬季-春季和夏季-秋季都将有助于了解鱼类肌肉中[THg]的变化。
