Pedersen Adam F, Fisk Aaron T, McMeans Bailey C, Dietz Rune, Sonne Christian, Rosing-Asvid Aqqalu, Ferguson Steven H, McKinney Melissa A
Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, QC H9X 3V9, Canada.
Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON N9B 3P4, Canada.
Sci Total Environ. 2025 Jan 25;962:178232. doi: 10.1016/j.scitotenv.2024.178232. Epub 2025 Jan 11.
Mercury (Hg) and persistent organic pollutant (POP) accumulation among species and biomagnification through food webs is typically assessed using stable isotopes of nitrogen (δN) and carbon (δC) in bulk (whole) tissues. Yet, bulk isotopic approaches have limitations, notably from the potential overlap of isotope values from different dietary sources and from spatial variation in source (baseline) signals. Here, we explore the potential of fatty acid carbon isotopes (FA δC) to (1) evaluate the trophic structure of a marine food web, (2) distinguish feeding patterns among four marine mammal consumers, (3) trace contaminant biomagnification through a food web, and (4) explain interspecific variation in contaminants among high-trophic position predators. In the Cumberland Sound (CS) food web of Nunavut, Canada, ranging from zooplankton to Greenland shark (Somniosus microcephalus), FA δC values for the monounsaturated FAs, 20:1 and 22:1 isomers, did not vary across the food web, while the long-chain polyunsaturated FA, 22:6n3 showed δC values that were enriched by ~1.5 ‰ with each trophic position. Values of δC for shorter-chain and saturated FAs varied widely across this food web. In East Greenland (EG) marine mammals, FA δC values were significantly higher in migratory sub-Arctic species relative to Arctic residents. Linear models using FA δC as explanatory variables for contaminant concentrations demonstrated that baseline-corrected δC values of certain dietary FAs explained more variation in POP concentrations than did bulk stable isotopes in EG marine mammals. However, bulk δN better explained Hg variation in the CS food web. This study details the FA δC instrumental methods, such that other researchers can test this novel approach on other species, locations, and food webs to further evaluate whether the δC values of certain diet-derived FAs consistently show limited or predictable trophic fractionation and may therefore be useful for assessing the accumulation and biomagnification of lipophilic contaminants.
通常使用生物组织整体中的氮（δN）和碳（δC）稳定同位素来评估汞（Hg）和持久性有机污染物（POP）在物种间的积累以及通过食物网的生物放大作用。然而，整体同位素方法存在局限性，特别是不同饮食来源的同位素值可能重叠以及源（基线）信号存在空间变化。在此，我们探讨脂肪酸碳同位素（FA δC）在以下方面的潜力：（1）评估海洋食物网的营养结构；（2）区分四种海洋哺乳动物消费者的摄食模式；（3）追踪污染物通过食物网的生物放大作用；（4）解释高营养级捕食者之间污染物的种间差异。在加拿大努纳武特地区的坎伯兰湾（CS）食物网中，从浮游动物到格陵兰鲨（Somniosus microcephalus），单不饱和脂肪酸20:1和22:1异构体的FA δC值在整个食物网中没有变化，而长链多不饱和脂肪酸22:6n3的δC值随着每个营养级增加约1.5‰。短链和饱和脂肪酸的δC值在这个食物网中变化很大。在东格陵兰（EG）的海洋哺乳动物中，相对于北极居民，亚北极迁徙物种的FA δC值显著更高。使用FA δC作为污染物浓度解释变量的线性模型表明，在EG海洋哺乳动物中，某些饮食脂肪酸经基线校正后的δC值比整体稳定同位素能更好地解释POP浓度的变化。然而，整体δN能更好地解释CS食物网中的汞变化。本研究详细介绍了FA δC的检测方法，以便其他研究人员能够在其他物种、地点和食物网上测试这种新方法，以进一步评估某些饮食来源脂肪酸的δC值是否始终显示出有限或可预测的营养分馏，因此可能有助于评估亲脂性污染物的积累和生物放大作用。
