The cyanobacteria Trichodesmium are broadly distributed in the photic zone of oligotrophic tropical and subtropical waters. Mesoscale physical processes associated with Kuroshio Extension (KE) can be important regulators of variability in Trichodesmium diversity and distribution. We investigated the spatial patterns, temporal variability, and regulations of Trichodesmium population across the KE in the northern Pacific Ocean (23°–40° N, 145°–160° E). Repeated surveys were conducted in May and September 2017. Spatial–temporal variability in the physicochemical variables between the two voyages was substantially attributed to the intensity and structure of KE and its recirculation gyres. The low temperature/high salinity conditions in May were reversed in September. Nutrients, DO, and suspended particulate matter (SPM) in May were higher than in September, while the opposite pattern was observed for pH. The spatial pattern of Trichodesmium volumetric abundance and calculated biomass was patchy, rather than varying consistently with latitude or longitude. T. thiebautii was more abundant in September, whereas T. erythraeum and T. hildebrandtii were similarly abundant in May and September. Temporal variability in Trichodesmium population abundance suggested the most suitable conditions of Trichodesmium distribution were a temperature of 26–30°C in a low Chl a environment with deep nutricline at 100–150 m. Specifically to different Trichodesmium species, salinity was a critical factor for abundant T. hildebrandtii, however, low N/P ratio and phosphate concentration facilitated higher abundance of T. thiebatuii and T. erythraeum. Finally, we confirmed anticyclonic and cyclonic eddies generated by the detachment of the Kuroshio had positive and negative impacts on Trichodesmium diversity and abundance, respectively.

蓝藻Trichodesmium广泛分布于贫营养热带和亚热带水域的透光区。与黑潮扩展 (KE) 相关的中尺度物理过程可能是Trichodesmium多样性和分布变异性的重要调节因子。我们调查了Trichodesmium的空间模式、时间变异性和规则北太平洋（23°–40° N，145°–160° E）的 KE 人口。2017 年 5 月和 9 月进行了重复调查。两次航行之间物理化学变量的时空变化主要归因于 KE 及其再循环环流的强度和结构。5 月的低温/高盐状况在 9 月发生逆转。5 月份的营养素、溶解氧和悬浮颗粒物 (SPM) 高于 9 月份，而 pH 值则相反。Trichodesmium体积丰度和计算出的生物量的空间格局是零散的，而不是随纬度或经度而变化。吨。thiebautii在 9 月更为丰富，而T. erythraeum和T. hildebrandtii在 5 月和 9 月同样丰富。Trichodesmium种群丰度的时间变化表明， Trichodesmium分布的最合适条件是在 26-30°C 的低 Chl a环境中，在 100-150 m 处有深的纽崔兰。具体到不同的Trichodesmium物种，盐度是丰富的T的关键因素。hildebrandtii然而，低 N/P 比和磷酸盐浓度促进了更高丰度的T。thiebatuii和T。红曲霉. 最后，我们证实了黑潮分离产生的反气旋和气旋涡流分别对Trichodesmium的多样性和丰度产生了积极和消极的影响。