Section of Marine Ecology and Biotechnology, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Environ Sci Technol. 2010 Oct 15;44(20):7964-9. doi: 10.1021/es1011274.
We explored the roles of mercury speciation on the bioaccumulation (both aqueous and dietary uptake and elimination) of inorganic mercury (Hg[II]) and methylmercury (MeHg) in tilapia (Oreochromis niloticus) by controlling the mercury binding to inorganic and organic ligands. For the aqueous uptake, we showed that the uptake rates of Hg(II) were significantly higher at 0 psu compared with those at 10 psu and 28 psu. Based on the mercury-Cl complexes distribution, we found a positive relationship between the Hg(II) aqueous uptake rate and the abundance of neutral HgCl(2). Such relationship was further confirmed by the uptake experiments conducted over a lower salinity range (0-6 psu), suggesting that HgCl(2)(0) was the predominant species taken up by tilapia. In the presence of dissolved organic carbon (DOC) from different sources (Suwannee River and natural local waters), mercury uptake rates all decreased dramatically over a wide range of salinity, especially for Hg(II), indicating the overwhelming influence of DOC as opposed to the single effect of salinity. Using the mercury-Cl-DOC model, we demonstrated for the first time that the inhibition of DOC was dependent on the Cl(-), which was less significant at middle salinity level for both mercury forms. In contrast to the complex influence of water conditions on dissolved uptake, we found no significant influence of acclimated salinity on the dietary assimilation and elimination of both mercury species in tilapia. Our results demonstrated the importance of speciation in understanding the mercury bioaccumulation in various natural systems and its broad biogeochemical cycling.
我们通过控制汞与无机和有机配体的结合，探讨了汞形态对罗非鱼（Oreochromis niloticus）体内无机汞（Hg[II]）和甲基汞（MeHg）的生物积累（包括水相和膳食摄入与消除）的作用。对于水相摄入，我们表明，与在 10 psu 和 28 psu 相比，0 psu 下 Hg(II)的摄入率显著更高。基于汞-氯络合物的分布，我们发现 Hg(II)水相摄入率与中性 HgCl(2)的丰度呈正相关。这种关系在更低盐度范围（0-6 psu）下进行的摄入实验中得到了进一步证实，表明 HgCl(2)(0)是罗非鱼摄入的主要形态。在来自不同来源（苏万尼河和天然当地水）的溶解有机碳（DOC）存在的情况下，汞的摄入率在很宽的盐度范围内都急剧下降，特别是对于 Hg(II)，这表明 DOC 的影响很大，而不是盐度的单一影响。使用汞-氯-DOC 模型，我们首次证明了 DOC 的抑制作用取决于 Cl(-)，对于两种汞形态，在中等盐度水平下 Cl(-)的影响较小。与水条件对溶解摄入的复杂影响不同，我们发现，对于罗非鱼来说，适应盐度对两种汞形态的膳食同化和消除均无显著影响。我们的研究结果表明，形态在理解各种自然系统中的汞生物积累及其广泛的生物地球化学循环中具有重要意义。
