Toxic algae and sea-loch sediments: A novel investigation to understand the influence of climate change on harmful algal blooms and aquaculture

贝类水产养殖对人类健康的全球性威胁来自有害的，特别是产生生物毒素的海洋浮游植物（通常称为有害藻华，HABs）。这些生物毒素在贝类的肉中积累，可以达到有害的浓度。食用受这些毒素污染的贝类肉会对人体健康构成严重威胁。在欧洲，人类健康受到欧盟贝类卫生指令的保护，该指令根据贝类毒素浓度超过监管限制，强制执行关闭贝类捕捞系统。这种关闭对该行业的经济产生了明显的负面影响，自1991年开始例行监测以来，几乎每年都在苏格兰水域实施。苏格兰政府目前正在促进苏格兰贝类产业的扩张，但目前没有机制来评估新地点对有害藻华或气候变化对其贝类床的影响的脆弱性。因此，迫切需要更好地了解有害浮游植物动态和毒性的控制过程，以便更好地监测、评估沿海水域的风险和管理，以保障人类健康并促进贝类产业的可持续性和扩大。目前存在多种贝类中毒综合征，由于中毒综合征的严重性，麻痹性贝类中毒（PSP）是全球最重要的中毒综合征之一。这种潜在的致命疾病是由于摄入了一种叫做蛤蚌毒素的神经毒素。在物种复杂的塔玛兰Alexandrium tamarense内的鞭毛藻是包括苏格兰水域在内的世界范围内PSP毒素的有力生产者。1968年，英国开始在英格兰东北海岸监测PSP毒素的存在，并于1990年在苏格兰海岸扩大监测范围，以应对PSP的一次重大事件。1996年，对水柱中亚历山大藻属的监测开始，揭示了水柱中亚历山大藻细胞和贝类中PSP毒性检测的“热点”的出现。常规监测显示，在苏格兰贝类中亚历山大藻细胞的丰度和毒性都有相当大的年代性变化。目前原因尚不清楚。目前的挑战是延长苏格兰1990年之前的记录，以了解在更长的时间尺度上这些环境中发生了什么，当有良好的气候数据可以帮助理解潜在的强迫机制时。二鞭毛藻tamarense提供了一个独特的机会来解决这一数据的缺乏。作为其有性生命周期的一部分，在其生长季节结束时，亚历山大菌细胞形成合子，合子融合形成一个健壮的囊肿。这个囊沉到海底，在沉积物上越冬，直到第二年它孵化并经历减数分裂形成营养细胞和随后的开花。并不是所有的囊肿都会孵化，留在沉积物中的囊肿可以作为前几年亚历山大藻华多样性的“足迹”。这种沉积囊肿记录，特别是在苏格兰海湖的庇护和限制交换环境中，海洋水产养殖集中，有可能告知我们对自然气候变化的理解，并保存亚历山大菌多样性的记录。因此，该项目将在与水产养殖和气候变化有关的有害藻华研究和咨询方面建立新的能力。该项目提供了令人兴奋的新机会，将目前通过监测方案获得的对HAB浮游生物动态的了解直接与沉积记录联系起来；从而能够首次系统地评估这些沉积物中可存活的有害藻华囊对水产养殖构成的风险，以及气候变化对年代际变化的影响。

A worldwide threat to human health from shellfish aquaculture comes from harmful, and particularly biotoxin producing, marine phytoplankton (often termed harmful algal blooms, HABs). These biotoxins accumulate in the shellfish flesh and can reach harmful concentrations. Consumption of shellfish flesh contaminated with these toxins can pose a serious risk to human health.In Europe, human health is protected by the EU Shellfish Hygiene Directive which enforce a system of shellfish harvesting closures based on concentrations of shellfish toxins above a regulatory limit. Such closures have a marked negative impact on the economics of the industry and have been enforced in Scottish waters on an almost annual basis since routine monitoring began in 1991. The Scottish Government is currently promoting an expansion of the shellfish industry in Scottish, but there is currently no mechanism to assess the vulnerability of new sites to the impacts of HABs or climate change on their shellfish beds. Improved understanding of the processes that govern harmful phytoplankton dynamics and toxicity is therefore urgently required to allow better monitoring, assessment of risk and management of coastal waters to safeguard human health and promote the sustainability and expansion of the shellfish industry.A number of shellfish poisoning syndromes exist, of which, owing to the severity of the intoxication syndrome, paralytic shellfish poisoning (PSP) is one of the most important globally. This potentially fatal condition results from the ingestion of neurotoxins called saxitoxins. Dinoflagellates within the species complex Alexandrium tamarense are potent producers of PSP toxins worldwide including Scottish waters. Monitoring for the presence of PSP toxins in the UK began along the northeast coast of England in 1968 and was expanded along the Scottish coasts in 1990 in response to a major PSP event. In 1996 monitoring for the dinoflagellate genus Alexandrium in the water column was initiated revealing the occurrence of 'hot-spots' for both the detection of Alexandrium cells in the water column and PSP toxicity in shellfishRoutine monitoring has revealed considerable interannual variation both in the abundance of Alexandrium cells alongside a decreasing trend in the toxicity recorded in Scottish shellfish. The cause for this is currently unknown. The current challenge is to extend the Scottish record prior to 1990 to understand what happened in these environments over longer time-scales when good climate data are available to help understand potential forcing mechanisms.The dinoflagellate Alexandrium tamarense presents a unique opportunity to address this lack of data. As part of its sexual life cycle, at the end of its growing season, Alexandrium cells form zygotes which fuse to form a robust cyst. This cyst sinks to the seabed and overwinters on the sediment until the following year when it hatches and undergoes meiotic division to form vegetative cells and subsequent blooms. Not all of the cysts will hatch and cysts that remain in the sediment can act as a 'footprint' of the diversity of the Alexandrium bloom during preceding years. This sedimentary cyst record, particularly in the sheltered and restricted exchange environments of Scotland's sea-lochs where marine aquaculture is concentrated, holds the potential to inform our understanding of natural climate variability as well as preserving a record of the Alexandrium diversity.The project will therefore build a new capacity in HABs research and advice in relation to aquaculture and climate change. The project provides exciting new opportunities to link current understanding of HAB plankton dynamics available through monitoring programmes directly to the sedimentary record; thereby enabling the first systematic evaluation of the risks posed to aquaculture from viable HAB cysts in these sediments and how decadal variation may be influenced by climate change.