Department of Biology, San Diego State University, San Diego, CA, USA.
NOAA-National Marine Fisheries Service, Southwest Fisheries Science Center, La Jolla, CA, USA.
Environ Res. 2021 Aug;199:111398. doi: 10.1016/j.envres.2021.111398. Epub 2021 May 28.
Aquatic pollution is known to reduce biodiversity and disrupt wildlife populations. Mercury (Hg) pollution is pervasive worldwide, contributing to the degradation of ecosystems, and causing deleterious effects to exposed organisms and populations. Batoids have a life history linked to the benthic substrate of coastal areas and occupy upper trophic levels. These combined with large bodies, long lifespan, and slow growth rates contributes to increased uptake and accumulation of Hg. However, mechanisms governing these associations are not well understood. Using multiple biogeochemical tracers (δC, δN and total Hg), we describe trophic interactions of three sympatric batoid species inhabiting an urbanized estuary and identify diet sources that contribute to Hg accumulation and trophic position among these mesopredators. We also use the Bat-ray (Myliobatis californica) as a model species, to compare diet composition, trophic position, and isotopic niche between two populations in two Californian bays. Trophic plasticity in M. californica was characterized by isotopic niche, diet proportions, and trophic position estimates using Bayesian statistics. We found diet and local contamination background strongly associated with Hg accumulation, and Hg levels that exceed EPA water quality criterion (<0.3 μg.g w.w.) in all studied species.
水生污染被认为会降低生物多样性并破坏野生动物种群。汞（Hg）污染在全球范围内普遍存在，导致生态系统退化，并对暴露的生物和种群造成有害影响。鳐形目动物的生活史与沿海地区的海底基质有关，并占据较高的营养级。加上体型大、寿命长、生长速度慢，导致它们对汞的吸收和积累增加。然而，这些关联的机制尚未得到很好的理解。本研究使用多种生物地球化学示踪剂（δC、δN 和总汞），描述了栖息在城市化河口的三种共生鳐形目物种的营养相互作用，并确定了导致这些中型捕食者体内汞积累和营养级的饮食来源。我们还使用蝠鲼（Myliobatis californica）作为模型物种，比较了加利福尼亚湾两个海湾中两个种群的饮食组成、营养级和同位素生态位。通过贝叶斯统计，我们发现鳐形目动物的营养可塑性表现在同位素生态位、饮食比例和营养级估计值上。我们发现，饮食和当地污染背景与汞积累密切相关，所有研究物种的汞含量均超过了 EPA 水质标准（<0.3μg.g w.w.）。
