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一个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，HAB）。这些生物毒素在贝类肉中积累，可达到有害浓度。食用受这些毒素污染的贝类肉会对人体健康构成严重风险。在欧洲，人体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度实施贝类捕捞关闭制度。这种关闭对该行业的经济产生了明显的负面影响，自1991年开始进行例行监测以来，几乎每年都在苏格兰沃茨强制执行。苏格兰政府目前正在促进扩大苏格兰的贝类产业，但目前没有机制评估新地点易受有害生物或气候变化对其贝类床的影响。因此，迫切需要提高对控制有害浮游植物动态和毒性的过程的理解，以便更好地监测、评估风险和管理沿海沃茨，以保障人类健康并促进贝类产业的可持续性和发展。麻痹性贝毒（PSP）是世界上最严重的贝类中毒之一。这种潜在的致命疾病是由于摄入了称为石房蛤毒素的神经毒素。塔玛亚历山大藻（Alexandrum tamarense）是世界范围内的甲藻，包括苏格兰沃茨，都是PSP毒素的强有力生产者。1968年，英国开始沿着英格兰东北海岸监测PSP毒素的存在，1990年，为了应对一次重大PSP事件，沿着苏格兰海岸扩大了监测范围。在1996年开始监测的甲藻属Alexandrum的水柱揭示了“热点”的发生，无论是Alexandrum细胞的检测在水柱和PSP的毒性贝类常规监测显示相当大的年际变化都在丰富的Alexandrum细胞的同时，在苏格兰贝类记录的毒性下降的趋势。造成这种情况的原因目前尚不清楚。当前的挑战是扩展1990年之前的苏格兰记录，以了解这些环境在更长的时间尺度上发生了什么，此时可以获得良好的气候数据来帮助了解潜在的强迫机制。甲藻塔玛亚历山大藻提供了一个独特的机会来解决这个问题缺乏数据。作为其性生活周期的一部分，在其生长季节结束时，亚历山大藻细胞形成受精卵，受精卵融合形成坚固的囊肿。这种孢囊沉到海底，在沉积物上越冬，直到第二年孵化，经历减数分裂形成营养细胞，随后开花。并不是所有的孢囊都会孵化，留在沉积物中的孢囊可以作为前几年亚历山大藻水华多样性的“足迹”。这种沉积囊肿记录，特别是在海水养殖集中的苏格兰海湖的遮蔽和限制交换环境中，有可能为我们了解自然气候变化以及保存亚历山大藻多样性的记录提供信息。因此，该项目将建立与水产养殖和气候变化有关的有害生物研究和咨询的新能力。该项目提供了令人兴奋的新机会，通过监测方案将目前对有害藻华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行的有害藻华包囊对水产养殖造成的风险，以及气候变化如何影响十年变化。

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.