Abstract：
Harmful algal bloom (HAB) toxins consumed by marine predators through fish prey can be lethal but studies on the resulting population consequences are lacking. Over the past approximately 20 years there have been large regional declines in some harbour seal populations around Scotland. Analyses of excreta (faeces and urine from live and dead seals and faecal samples from seal haulout sites) suggest widespread exposure to toxins through the ingestion of contaminated prey. A risk assessment model, incorporating concentrations of the two major HAB toxins found in seal prey around Scotland (domoic acid (DA), and saxitoxins (STX)), the seasonal persistence of the toxins in the fish and the foraging patterns of harbour seals were used to estimate the proportion of adults and juveniles likely to have ingested doses above various estimated toxicity thresholds. The results were highly dependent on toxin type, persistence, and foraging regime as well as age class, all of which affected the proportion of exposed animals exceeding toxicity thresholds. In this preliminary model STX exposure was unlikely to result in mortalities. Modelled DA exposure resulted in doses above an estimated lethal threshold of 1900 µg/kg body mass affecting up to 3.8 % of exposed juveniles and 5.3 % of exposed adults. Given the uncertainty in the model parameters and the limitations of the data these conclusions should be treated with caution, but they indicate that DA remains a potential factor involved in the regional declines of harbour seals. Similar risks may be experienced by other top predators, including small cetaceans and seabirds that feed on similar prey in Scottish waters.
摘要：
海洋捕食者通过鱼类猎物消耗的有害藻华（HAB）毒素可能是致命的，但缺乏对由此产生的种群后果的研究。在过去的大约20年中，苏格兰周围的一些港口海豹种群的区域性下降幅度很大。对排泄物（活海豹和死海豹的粪便和尿液以及海豹拖运地点的粪便样品）的分析表明，通过摄入受污染的猎物，广泛暴露于毒素。风险评估模型，结合了在苏格兰周围海豹猎物中发现的两种主要HAB毒素的浓度(海藻酸(DA)，和蛇毒素（STX），鱼类中毒素的季节性持久性和海豹的觅食模式被用来估计成年和少年可能摄入超过各种估计毒性阈值的剂量的比例。结果高度依赖于毒素类型，持久性,觅食制度和年龄组，所有这些都影响了超过毒性阈值的暴露动物的比例。在此初步模型中，STX暴露不太可能导致死亡率。模拟的DA暴露导致剂量超过估计的致死阈值1900µg/kg体重，影响多达3.8％的暴露青少年和5.3％的暴露成年人。鉴于模型参数的不确定性和数据的局限性，这些结论应谨慎对待，但它们表明，DA仍然是导致海豹区域性下降的潜在因素。其他顶级捕食者可能会遇到类似的风险，包括在苏格兰水域以类似猎物为食的小型鲸目动物和海鸟。
