The cost of gold: Mercury contamination of fishes in a Neotropical river food web

Abstract In South America, mercury contamination due to gold mining operations is a threat to both biodiversity and human health. We examined mercury (Hg) concentrations in fishes that constitute important subsistence fisheries from mined and non-mined tributaries in the middle Mazaruni River, Guyana. Mercury concentrations and trophic food web structure (based on carbon and nitrogen stable isotopes) were characterized for primary basal sources and 39 fish species representing seven trophic guilds. Fishes collected at mined sites had higher mercury concentrations; piscivores and carnivores had the highest Hg concentrations and exhibited significant Hg biomagnification. Our results showed that medium- to large-bodied fishes commonly eaten by local people contained Hg values that exceed the World Health Organization (WHO) criteria, and pose a health concern for riverine communities along the Mazaruni River that depend on fish as their main source of protein. Further research to determine the sources of Hg contamination and how it affects human health in this neotropical river must become a top priority. In addition, more research on how Hg contamination impacts the fishes themselves and overall aquatic biodiversity is also needed in the Mazaruni River which has both high fish endemism and diversity.

摘要 在南美洲，金矿开采活动引发的汞污染对生物多样性与人类健康均构成威胁。本研究针对圭亚那马扎鲁尼河中游受采矿影响与未受采矿影响的支流中，作为当地重要自给性渔业资源的鱼类，检测了其体内汞（Hg）含量。研究对初级营养基底源以及代表7个营养功能群的39种鱼类，开展了汞浓度与食物网营养结构（基于碳、氮稳定同位素）的特征分析。结果显示，采自采矿点的鱼类体内汞浓度更高；食鱼鱼类与肉食性鱼类的汞浓度最高，且呈现出显著的汞生物放大效应。本研究结果表明，当地居民常食用的中大型鱼类体内汞含量超过了世界卫生组织（World Health Organization, WHO）的安全标准，对以鱼类为主要蛋白质来源的马扎鲁尼河沿岸沿河社区构成健康风险。明确该新热带河流中汞污染的来源及其对人类健康的影响，应成为后续研究的首要任务。此外，马扎鲁尼河拥有极高的鱼类特有种丰富度与物种多样性，针对汞污染对鱼类本身以及整体水生生物多样性的影响，仍需开展更多研究。