Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido 041-8611, Japan; Tokyo Institute of Technology, School of Environment and Society, 2-12-1-M1-4 Ookayama, Meguro, Tokyo 152-8552, Japan.
National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Kanagawa 236-8648, Japan.
Harmful Algae. 2017 Mar;63:13-22. doi: 10.1016/j.hal.2017.01.001. Epub 2017 Jan 22.
Abundant cyst distributions of the toxic dinoflagellate Alexandrium fundyense (previous A. tamarense north American clade) were recently observed on the north Chukchi Sea shelf and on the eastern Bering Sea shelf, suggesting that A. fundyense is both highly adapted to the local environments in the high latitude areas and might cause toxin contamination of plankton feeders. However, little is known about the physiological characteristics and toxin profiles of A. fundyense in these areas, which are characterized by low water temperatures, weak sunlight, and more or less permanent ice cover during winter. To clarify the physiological characteristics of A. fundyense, the effects of water temperature and light intensity on the vegetative growth and toxin profiles of this species were examined using A. fundyense strains isolated from one sediment sample collected from each area. Using the same sediments samples, seasonal changes of the cyst germination in different water temperatures were investigated. Vegetative cells grew at temperatures as low as 5°C and survived at 1°C under relatively low light intensity. They also grew at moderate water temperatures (10-15°C). Their cysts could germinate at low temperatures (1°C) and have an endogenous dormancy period from late summer to early spring, and warmer water temperatures (5-15°C) increased germination success. These physiological characteristics suggest that A. fundyense in the Chukchi Sea and eastern Bering Sea is adapted to the environments of high latitude areas. In addition, the results suggest that in the study areas A. fundyense has the potential to germinate and grow when water temperatures increase. Cellular toxin amounts of A. fundyense strains from the eastern Bering Sea and Chukchi Sea were ranged from 7.2 to 38.2 fmol cell. These toxin amounts are comparable with A. fundyense strains isolated from other areas where PSP toxin contamination of bivalves occurs. The dominant toxin of the strains isolated from the Chukchi Sea was saxitoxin, while most A. fundyense strains from the eastern Bering Sea are dominated by the C2 toxin. Toxin profiles similar to those detected in Chukchi Sea have not been reported by any previous research. The dominance of a highly toxic PST variant in Chukchi A. fundyense suggests that presence of the species at low cell concentrations may cause toxin contamination of predators. This study revealed that abundant A. fundyense cysts deposited on the eastern Bering Sea and Chukchi Sea shelves potentially germinate and grow with PSP toxin contents in the local environments. In conclusion, a high risk of PSP occurrences exists on the eastern Bering Sea and Chukchi Sea shelves.
大量的有毒甲藻亚历山大藻丰度（以前的北美 A. 塔玛瑞塞利种系）囊泡最近在楚科奇海大陆架和东白令海大陆架被发现，这表明亚历山大藻丰度高度适应高纬度地区的当地环境，并且可能导致浮游动物饵料的毒素污染。然而，对于这些地区的亚历山大藻丰度的生理特征和毒素特征，人们知之甚少，这些地区的特点是冬季水温低、阳光弱，或多或少存在永久性冰盖。为了阐明亚历山大藻丰度的生理特征，使用从每个地区采集的一个沉积物样本中分离的亚历山大藻丰度菌株，研究了水温和光照强度对该物种的营养生长和毒素特征的影响。利用相同的沉积物样本，研究了不同水温下休眠孢囊的季节性萌发变化。营养细胞在低至 5°C 的温度下生长，在相对较低的光照强度下可以存活于 1°C。它们也在中等水温（10-15°C）下生长。它们的休眠孢囊可以在低温（1°C）下萌发，并且在夏末到早春期间具有内源性休眠期，而较暖的水温（5-15°C）增加了萌发成功率。这些生理特征表明，楚科奇海和东白令海中的亚历山大藻丰度适应高纬度地区的环境。此外，研究结果表明，在研究区域，当水温升高时，亚历山大藻丰度有萌发和生长的潜力。来自东白令海和楚科奇海的亚历山大藻丰度菌株的细胞毒素含量范围为 7.2 到 38.2 fmol 细胞。这些毒素含量与发生贝类麻痹性贝类毒素污染的其他地区分离的亚历山大藻丰度菌株相当。来自楚科奇海的菌株的主要毒素是石房蛤毒素，而来自东白令海的大多数亚历山大藻丰度菌株则以 C2 毒素为主。在以前的任何研究中都没有报道过在楚科奇海检测到的类似毒素特征。在楚科奇海的亚历山大藻丰度中，高毒性 PST 变体的优势表明，在低细胞浓度下存在该物种可能导致捕食者的毒素污染。本研究表明，大量沉积在东白令海和楚科奇海大陆架上的亚历山大藻丰度休眠孢囊有可能在当地环境中萌发和生长，并具有麻痹性贝类毒素含量。总之，在东白令海和楚科奇海大陆架上存在麻痹性贝类毒素发生的高风险。
