Bird Mercury Concentrations Change Rapidly as Chicks Age: Toxicological Risk is Highest at Hatching and Fledging
Bird Mercury Concentrations Change Rapidly as Chicks Age: Toxicological Risk is Highest at Hatching and Fledging
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DOI：
10.1021/es200647g
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发表时间：
2011-06-15
影响因子：
11.4
通讯作者：
Herzog, Mark P.
中科院分区：
文献类型：
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作者：
Ackerman, Joshua T.;Eagles-Smith, Collin A.;Herzog, Mark P.
由于随着雏鸟年龄的增长，汞浓度具有高度短暂性，因此幼鸟接触甲基汞的毒理学风险很复杂。我们检测了加利福尼亚州旧金山湾汞污染程度低或高的湿地中的 111 只福斯特燕鸥 (Sterna forsteri)、69 只黑颈长脚鹬 (Himantopus mexicanus) 和 43 只美洲反嘴鹬 (Recurvirostra americana) 雏鸟从孵化到羽化后的整个过程中血液、肝脏、肾脏、肌肉和羽毛中的总汞和甲基汞浓度。对于每种水鸟物种、内部组织和湿地，总汞和甲基汞浓度随着雏鸟年龄的增长而迅速变化，并从孵化到羽化后呈现出二次U形模式。由于母体在鸡蛋中沉积了汞，汞浓度在孵化后立即达到最高，然后随着雏鸡的年龄增长而迅速下降，并通过尺寸的增长和汞净化到生长的羽毛中稀释了体内的汞负荷。当体重增加和羽毛生长减慢时，汞浓度在羽化过程中增加，而雏鸡继续摄入膳食汞。与内部组织中的汞相比，小鸡羽毛中的汞浓度变化很大，并且随着年龄的增长而线性下降。对于 58 只重新捕获的福斯特燕鸥雏鸟，血汞浓度的比例变化与体重的比例变化呈负相关，但与羽毛数量或翅膀长度无关。因此，在采样期间体重增加的雏鸡中，汞浓度下降得更多。从孵化到长出羽毛的汞浓度呈 U 形模式表明，幼鸟在孵化后不久可能面临最高的甲基汞中毒风险，此时母体沉积的汞浓度仍然很高，而在长出羽毛后，质量稀释和汞排泄到羽毛中的机会受到限制。
Toxicological risk of methylmercury exposure to juvenile birds is complex due to the highly transient nature of mercury concentrations as chicks age. We examined total mercury and methylmercury concentrations in blood, liver, kidney, muscle, and feathers of 111 Forster's tern (Sterna forsteri), 69 black-necked stilt (Himantopus mexicanus), and 43 American avocet (Recurvirostra americana) chicks as they aged from hatching through postfledging at wetlands that had either low or high mercury contamination in San Francisco Bay, California. For each water-bird species, internal tissue, and wetland, total mercury and methylmercury concentrations changed rapidly as chicks aged and exhibited a quadratic, U-shaped pattern from hatching through postfledging. Mercury concentrations were highest immediately after hatching, due to maternally deposited mercury in eggs, then rapidly declined as chicks aged and diluted their mercury body burden through growth in size and mercury depuration into growing feathers. Mercury concentrations then increased during fledging when mass gain and feather growth slowed, while chicks continued to acquire dietary mercury. In contrast to mercury in internal tissues, mercury concentrations in chick feathers were highly variable and declined linearly with age. For 58 recaptured Forster's tern chicks, the proportional change in bloodmercury concentration was negatively related to the proportional change in body mass, but not to the amount of feathers or wing length. Thus, mercury concentrations declined more in chicks that gained more mass between sampling events. The U-shaped pattern of mercury concentrations from hatching to fledging indicates that juvenile birds may be at highest risk to methylmercury toxicity shortly after hatching when maternally deposited mercury concentrations are still high and again after fledging when opportunities for mass dilution and mercury excretion into feathers are limited.