The Santa Barbara Channel, CA (SBC) is a biodiverse marine ecosystem fueled largely by phytoplankton productivity, and the composition of the phytoplankton community influences the magnitude and fates of this productivity. Here, we create a 22-year monthly time series of phytoplankton biomarker pigment concentrations in the SBC by combining 12 years of high performance liquid chromatography phytoplankton pigment concentrations with bio-optical models and 10 additional years of bio-optical observations. The bio-optical models skillfully predict biomarker pigment concentrations representative of five distinct phytoplankton groups (PGs; diatoms, dinoflagellates, chlorophytes, prymnesiophytes, and picophytoplankton) and resolve seasonal responses to the annual upwelling-relaxation cycle for all PGs except the dinoflagellates. Our observations indicate that nanophytoplankton groups respond most rapidly to seasonal upwelling, followed by diatoms, and then by picophytoplankton as the water column stratifies in the summer. A Regional Ocean Modeling System (ROMS) solution is used to relate advection of different source waters to the observed PG dynamics. The ROMS simulation results suggest that, on seasonal time scales, pronounced cross-SBC differences in PG seasonality are related to cross-SBC differences in source waters. El Niño Southern Oscillation events drive interannual variability in the upwelling response of most PGs. On decadal time scales, dinoflagellate blooms are associated with the warm phase of the North Pacific Gyre Oscillation and anomalous advection of Southern California Bight source waters into the SBC. Taken together, our results provide a novel view of phytoplankton community succession in response to seasonal upwelling by considering the dynamics of pico- and nano-phytoplankton and suggest that regional surface ocean advection plays a substantial role in driving phytoplankton composition in the SBC.

加利福尼亚州圣巴巴拉海峡 (SBC) 是一个生物多样性海洋生态系统，主要由浮游植物生产力推动，浮游植物群落的组成影响这种生产力的大小和命运。在这里，我们通过将 12 年的高效液相色谱浮游植物色素浓度与生物光学模型和另外 10 年的生物光学观察相结合，创建了 SBC 中浮游植物生物标志物色素浓度的 22 年月度时间序列。生物光学模型巧妙地预测了代表五个不同浮游植物群（PG；硅藻、甲藻、叶绿藻、叶藻和微型浮游植物）的生物标志物色素浓度，并解决了除甲藻外的所有 PG 对年度上升流-松弛周期的季节性反应。我们的观察表明，纳米浮游植物群对季节性上升流的反应最快，其次是硅藻，然后是微型浮游植物，因为夏季水柱分层。区域海洋建模系统 (ROMS) 解决方案用于将不同源水的平流与观察到的 PG 动态联系起来。ROMS 模拟结果表明，在季节性时间尺度上，PG 季节性的显着跨 SBC 差异与源水跨 SBC 差异有关。厄尔尼诺南方涛动事件驱动了大多数 PG 上升流响应的年际变化。在年代际时间尺度上，甲藻的大量繁殖与北太平洋环流振荡的暖期和南加州湾源水进入 SBC 的异常平流有关。综合起来，