In 2016, an unprecedented Pseudo-nitzschia australis bloom in the Gulf of Maine led to the first shellfishery closures due to domoic acid in the region's history. In this paper, potential introduction routes of P. australis are explored through observations, a hydrodynamic model, and a Lagrangian particle tracking model. Based on particle tracking experiments, the most likely source of P. australis to the Gulf of Maine was the Scotian Shelf. However, in 2016, connectivity between the Scotian Shelf and the bloom region was not significantly different from the other years between 2012 and 2019, nor were temperature conditions more favorable for P. australis growth. Observations indicated changes on the Scotian Shelf in 2016 preceded the introduction of P. australis: increased bottom salinity and decreased surface salinity. The increased bottom salinity on the shelf may be linked to anomalously saline water observed near the coast of Maine in 2016 via transport through Northeast Channel. The changes in upstream water mass properties may be related to the introduction of P. australis, and could be the result of either increased influence of the Labrador Current or increased outflow from the Gulf of St. Lawrence. The ultimate source of P. australis remains unknown, although the species has previously been observed in the eastern North Atlantic, and connectivity across the ocean is possible via a subpolar route. Continued and increased monitoring is warranted to track interannual Pseudo-nitzschia persistence in the Gulf of Maine, and sampling on the Scotian Shelf should be conducted to map upstream P. australis populations.

2016 年，缅因湾史无前例的 Pseudo-nitzschia australis 水华导致该地区历史上首次因软骨藻酸而关闭的贝类养殖场。在本文中，通过观察、流体动力学模型和拉格朗日粒子跟踪模型，探索了P. australis的潜在引入途径。根据粒子追踪实验，缅因湾最有可能的P. australis来源是苏格兰大陆架。然而，在 2016 年，斯科舍大陆架和开花区之间的连通性与 2012 年至 2019 年的其他年份没有显着差异，温度条件也没有更利于P. australis的生长。观察表明 2016 年苏格兰大陆架的变化在引入P. australis：增加底部盐度和降低表面盐度。大陆架底部盐度的增加可能与 2016 年在缅因州海岸附近通过东北海峡的运输观察到的异常咸水有关。上游水团性质的变化可能与引入澳大利亚南芥有关，可能是拉布拉多海流影响增加或圣劳伦斯湾流出量增加的结果。P. australis的最终来源仍然未知，尽管该物种以前曾在北大西洋东部观察到，并且通过亚极地路线可以跨洋连接。有必要继续和加强监测以跟踪年际伪尼采缅因湾的持久性，并应在苏格兰大陆架上进行采样以绘制上游P. australis种群。