The Thomas Fire ignited on December 5, 2017 and burned nearly 300,000 acres of land in Ventura and Santa Barbara counties until January 12, 2018, making it the largest wildfire in California history at the time. During the fire, a persistent plume of ash, smoke, and soot extended up to 1,000 km offshore over the Santa Barbara Channel (SBC). The effect of this ash influx on the SBC phytoplankton community was investigated with an Imaging FlowCytobot (IFCB) onboard R/V Sally Ride during a research cruise in mid‐December 2017. Over 100,000 images of phytoplankton and nonliving particles were collected and each image was manually classified, resulting in time series of phytoplankton cells and detrital particles, including ash. Comparing the Thomas Fire conditions to historical monthly sampling in the SBC in December reveals significant differences in sea surface temperature, nutrient concentration, and phytoplankton community composition (PCC) in December 2017. During the Thomas Fire, dinoflagellates dominated the phytoplankton community (comprising up to 90% of the total phytoplankton cell biovolume per sample), while diatoms and picophytoplankton typically dominate surface ocean PCC in the SBC in December. While this study was not able to demonstrate a correlational relationship between PCC and wildfire ash concentration, the significant differences in surface ocean biogeochemistry in December 2017 compared to past winters is notable. Wildfire severity and frequency are annually increasing in California and globally with unknown impacts on the marine ecosystem; thus, this study provides an important baseline assessment for the SBC.

中文翻译：

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托马斯大火期间圣塔芭芭拉海峡浮游植物群落组成的观测

托马斯大火于2017年12月5日点燃，并烧毁了文图拉和圣塔芭芭拉县近30万英亩土地，直至2018年1月12日，使其成为当时加州历史上最大的野火。在大火中，持续不断的烟灰，烟尘和烟灰向圣巴巴拉海峡（SBC）延伸至离岸1000公里。在2017年12月中旬的一次研究航行中，通过R / V Sally Ride船上的Imaging FlowCytobot（IFCB）调查了灰烬涌入对SBC浮游植物群落的影响。收集了100,000多幅浮游植物和非生物颗粒的图像，每幅图像对图像进行人工分类，得出浮游植物细胞和碎屑颗粒（包括灰分）的时间序列。将托马斯大火条件与12月SBC的历史月度采样进行比较，发现2017年12月海面温度，养分浓度和浮游植物群落组成（PCC）存在显着差异。在托马斯大火期间，鞭毛鞭毛虫占浮游植物群落的主要部分（包括每个样本中浮游植物总生物量的90％），而在12月的SBC中，硅藻和浮游植物通常占据着表层海洋PCC。虽然这项研究无法证明PCC与野火灰浓度之间的相关关系，但与过去的冬季相比，2017年12月的海洋表面生物地球化学差异显着。加州乃至全球范围内，野火的严重性和频度逐年增加，对海洋生态系统的影响未知。从而，