US Geological Survey, Alaska Science Center, Anchorage, AK, United States.
US Geological Survey, Alaska Science Center, Anchorage, AK, United States.
Harmful Algae. 2020 Feb;92:101730. doi: 10.1016/j.hal.2019.101730. Epub 2019 Dec 23.
Elevated seawater temperatures are linked to the development of harmful algal blooms (HABs), which pose a growing threat to marine birds and other wildlife. During late 2015 and early 2016, a massive die-off of Common Murres (Uria aalge; hereafter, murres) was observed in the Gulf of Alaska coincident with a strong marine heat wave. Previous studies have documented illness and death among seabirds resulting from exposure to the HAB neurotoxins saxitoxin (STX) and domoic acid (DA). Given the unusual mortality event, corresponding warm water anomalies, and recent detection of STX and DA throughout coastal Alaskan waters, HABs were identified as a possible factor of concern. To evaluate whether algal toxins may have contributed to murre deaths, we tested for STX and DA in a suite of tissues obtained from beach-cast murre carcasses associated with the die-off as well as from apparently healthy murres and Black-legged Kittiwakes (Rissa tridactyla; hereafter, kittiwakes) sampled in the preceding and following summers. We also tested forage fish and marine invertebrates collected in the Gulf of Alaska in 2015-2017 to evaluate potential sources of HAB toxin exposure for seabirds. Saxitoxin was present in multiple tissue types of both die-off (36.4 %) and healthy (41.7 %) murres and healthy kittiwakes (54.2 %). Among birds, we detected the highest concentrations of STX in liver tissues (range 1.4-10.8 μg 100 g) of die-off murres. Saxitoxin was relatively common in forage fish (20.3 %) and invertebrates (53.8 %). No established toxicity limits currently exist for seabirds, but concentrations of STX in birds and forage fish in our study were lower than values reported from most other bird die-offs in which STX intoxication was causally linked. We detected low concentrations of DA in a single bird sample and in 33.3 % of invertebrates and 4.0 % of forage fish samples. Although these results do not support the hypothesis that acute exposure to STX or DA was a primary factor in the 2015-2016 mortality event, additional information about the sensitivity of murres to these toxins is needed before we can discount their potential role in the die-off. The widespread occurrence of STX in seabirds, forage fish, and invertebrates in the Gulf of Alaska indicates that algal toxins should be considered in future assessments of seabird health, especially given the potential for greater occurrence of HABs in the future.
升高的海水温度与有害藻类大量繁殖（HABs）的发展有关，这对海洋鸟类和其他野生动物构成了越来越大的威胁。2015 年末至 2016 年初，在阿拉斯加湾发生了大规模的普通海鸠（Uria aalge；以下简称海鸠）死亡事件，同时发生了强烈的海洋热浪。先前的研究记录了海鸟因暴露于 HAB 神经毒素石房蛤毒素（STX）和软骨藻酸（DA）而患病和死亡。鉴于异常死亡率、相应的暖水异常以及最近在整个阿拉斯加沿海水域检测到 STX 和 DA，因此 HAB 被确定为一个可能的关注因素。为了评估藻类毒素是否可能导致海鸠死亡，我们从与死亡事件相关的海滩海鸠尸体以及在前一年和随后的夏季采样的明显健康的海鸠和黑脚三趾鸥（Rissa tridactyla；以下简称三趾鸥）中获得的一系列组织中测试了 STX 和 DA。我们还测试了 2015-2017 年在阿拉斯加湾收集的食用鱼和海洋无脊椎动物，以评估 HAB 毒素暴露对海鸟的潜在来源。在死亡（36.4%）和健康（41.7%）的海鸠和健康的三趾鸥的多种组织类型中均存在石房蛤毒素。在鸟类中，我们在死亡海鸠的肝脏组织中检测到 STX 的最高浓度（范围为 1.4-10.8μg 100g）。石房蛤毒素在食用鱼（20.3%）和无脊椎动物（53.8%）中较为常见。目前尚无针对海鸟的既定毒性限值，但我们研究中的鸟类和食用鱼中的 STX 浓度低于大多数其他与 STX 中毒有关的鸟类死亡事件中报告的值。我们在单个鸟类样本以及 33.3%的无脊椎动物和 4.0%的食用鱼样本中检测到低浓度的软骨藻酸。尽管这些结果不支持急性暴露于 STX 或 DA 是 2015-2016 年死亡事件的主要因素的假设，但在排除它们在死亡事件中的潜在作用之前，还需要更多关于海鸠对这些毒素的敏感性的信息。石房蛤毒素在阿拉斯加湾的海鸟、食用鱼和无脊椎动物中的广泛存在表明，在未来对海鸟健康的评估中应考虑藻类毒素，特别是考虑到未来 HAB 发生的可能性增加。
