Summer bivalve shellfish mortalities have been observed in Puget Sound for nearly a century and attempts to understand and mitigate these losses have been only partially successful. Likewise, the understanding of the environmental conditions triggering shellfish mortalities and successful strategies for their mitigation are incomplete. In the literature, phytoplankton have played only a cursory role in summer shellfish mortalities in Washington State because spawning stress and bacteria were thought to be the primary causes. In recent years, the occurrence of Protoceratium reticulatum (Claparede & Lachmann) Buetschli and Akashiwo sanguinea (Hirasaka) Hansen & Moestrup, have been documented by the SoundToxins research and monitoring partnership in increasing numbers and duration and have been associated with declining shellfish health or mortality at various sites in Puget Sound. Blooms of these species occur primarily in summer months and have been shown to cause mass mortalities of shellfish in the U.S. and other parts of the world. In 2016-2017, yessotoxins (YTX) were measured in several species of Puget Sound bivalve shellfish, with a maximum concentration of 2.20 mg/kg in blue mussels, a value below the regulatory limit of 3.75 mg/kg established by the European Union for human health protection but documented to cause shellfish mortalities in other locations around the world. In July 2019, a bloom of P. reticulatum coincided with a summer shellfish mortality event, involving a dramatic surfacing of stressed, gaping Manila clams, suggesting that YTX could be the cause. YTX concentrations in their tissues were measured at a maximum of 0.28 mg/kg and histology of these clams demonstrated damage to digestive glands. A culture of P. reticulatum, isolated from North Bay during this massive bloom and shellfish mortality event, showed YTX reaching 26.6 pg/cell, the highest recorded toxin quota measured in the U.S. to date. Concentrations of YTX in phytoplankton samples reached a maximum of 920 ng/L during a P. reticulatum bloom in Mystery Bay on 13 August 2019 when cell abundance reached 1.82 million cells/L. The highest cellular YTX quota during that bloom that lasted into September was 10.8 pg/cell on 3 Sept 2019. Shellfish producers in Washington State have also noted shellfish larvae mortalities due to A. sanguinea passing through filtration intake systems into hatchery facilities. Early warning of shellfish-killing harmful algal bloom (HAB) presence in Puget Sound, through partnerships such as SoundToxins, provides options for shellfish growers to mitigate their effects through early harvest, movement of shellstock to upland facilities, or enhanced filtration at aquaculture facilities.

中文翻译：

---

隐藏在众目睽睽之下：华盛顿州的杀贝类浮游植物。

近一个世纪以来，普吉特海湾一直观察到夏季双壳贝类死亡，而试图了解和减轻这些损失的尝试只取得了部分成功。同样，对引发贝类死亡的环境条件和成功的缓解策略的理解是不完整的。在文献中，浮游植物在华盛顿州夏季贝类死亡中只起到了粗略的作用，因为产卵压力和细菌被认为是主要原因。近年出现网状原角藻（Claparede & Lachmann）Buetschli和Akashiwo sanguinea（平坂）Hansen & Moestrup，SoundToxins 研究和监测伙伴关系记录了越来越多的数量和持续时间，并且与普吉特海湾不同地点的贝类健康或死亡率下降有关。这些物种的开花主要发生在夏季，并已被证明会导致美国和世界其他地区的贝类大量死亡。2016-2017 年，在几种普吉特湾双壳贝类中检测到野毒毒素 (YTX)，蓝贻贝中的最高浓度为 2.20 毫克/公斤，低于欧盟制定的 3.75 毫克/公斤的监管限值。人类健康保护，但记录在世界其他地方导致贝类死亡。2019 年 7 月，P. reticulatum 的大量繁殖与夏季贝类死亡事件同时发生，其中包括显着的压力、张开的马尼拉蛤蜊，表明 YTX 可能是原因。测定其组织中的 YTX 浓度最高为 0.28 mg/kg，这些蛤蜊的组织学显示对消化腺的损害。在这次大规模的水华和贝类死亡事件期间，从北湾分离出的网状假单胞菌培养物显示 YTX 达到 26.6 pg/细胞，这是迄今为止在美国测得的最高记录毒素配额。在 2019 年 8 月 13 日神秘湾的网状浮游植物开花期间，浮游植物样品中的 YTX 浓度最高达到 920 ng/L，此时细胞丰度达到 182 万细胞/L。2019 年 9 月 3 日，在持续到 9 月的开花期间，最高细胞 YTX 配额为 10.8 皮克/细胞。华盛顿州的贝类生产商也注意到贝类幼虫因 A. 红血球通过过滤吸入系统进入孵化设施。通过 SoundToxins 等合作伙伴，对普吉特海湾中存在的杀死贝类的有害藻华 (HAB) 进行预警，为贝类养殖者提供了选择，以通过早期收获、将贝类转移到高地设施或加强水产养殖设施的过滤来减轻其影响。