State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
Environ Sci Technol. 2015 Apr 21;49(8):4911-20. doi: 10.1021/acs.est.5b00071. Epub 2015 Mar 31.
It is well-known that the body burden of hydrophobic organic compounds (HOCs) increases with the trophic level of aquatic organisms. However, the mechanism of HOC biomagnification is not fully understood. To fill this gap, this study investigated the effect of predation on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs), one type of HOC, in low-to-high aquatic trophic levels under constant freely dissolved PAH concentrations (1, 5, or 10 μg L(-1)) maintained by passive dosing systems. The tested PAHs included phenanthrene, anthracene, fluoranthene, and pyrene. The test organisms included zebrafish, which prey on Daphnia magna, and cichlids, which prey on zebrafish. The results revealed that for both zebrafish and cichlids, predation elevated the uptake and elimination rates of PAHs. The increase of uptake rate constant ranged from 20.8% to 39.4% in zebrafish with the amount of predation of 5 daphnids per fish per day, and the PAH uptake rate constant increased with the amount of predation. However, predation did not change the final bioaccumulation equilibrium; the equilibrium concentrations of PAHs in fish only depended on the freely dissolved concentration in water. Furthermore, the lipid-normalized water-based bioaccumulation factor of each PAH was constant for fish at different trophic levels. These findings infer that the final bioaccumulation equilibrium of PAHs is related to a partition between water and lipids in aquatic organisms, and predation between trophic levels does not change bioaccumulation equilibrium but bioaccumulation kinetics at stable freely dissolved PAH concentrations. This study suggests that if HOCs have not reached bioaccumulation equilibrium, biomagnification occurs due to enhanced uptake rates caused by predation in addition to higher lipid contents in higher trophic organisms. Otherwise, it is only due to the higher lipid contents in higher trophic organisms.
众所周知，疏水有机化合物（HOCs）在水生生物中的体负荷随着营养水平的升高而增加。然而，HOC 生物放大的机制尚未完全阐明。为了填补这一空白，本研究在通过被动给药系统维持的恒定自由溶解 HOC 浓度（1、5 或 10μg/L）下，调查了捕食对低至高水生营养级中多环芳烃（PAHs）一种 HOC 的生物积累的影响。测试的 PAHs 包括菲、蒽、荧蒽和芘。测试生物包括捕食大型溞的斑马鱼和捕食斑马鱼的慈鲷。结果表明，对于斑马鱼和慈鲷，捕食均提高了 PAHs 的吸收和消除率。在每天每条鱼捕食 5 只大型溞的情况下，斑马鱼的吸收率常数增加了 20.8%至 39.4%，并且 PAH 吸收率常数随捕食量的增加而增加。然而，捕食并没有改变最终的生物积累平衡；鱼类中 PAHs 的平衡浓度仅取决于水中的自由溶解浓度。此外，不同营养级鱼类的每种 PAH 的脂化水基生物积累因子保持不变。这些发现推断出 PAHs 的最终生物积累平衡与水生生物中水体和脂类之间的分配有关，并且营养级之间的捕食不会改变生物积累平衡，而是在稳定的自由溶解 PAH 浓度下改变生物积累动力学。本研究表明，如果 HOC 尚未达到生物积累平衡，则由于捕食导致的吸收速率增加以及更高营养级生物中更高的脂质含量而发生生物放大。否则，这仅仅是由于更高营养级生物中更高的脂质含量所致。
