Abstract Coinciding with the marine heat wave in 2014 and a strong El Nino in 2016, blooms of the tropical-temperate pelagic colonial tunicate, Pyrosoma atlanticum, expanded into the Northern California Current (NCC). Given the high densities of P. atlanticum colonies observed in the NCC, and their potential for high grazing rates, we hypothesized that the species could have a substantial negative effect on the phytoplankton standing stock in the Northeastern Pacific Ocean. In the late winter, spring and early autumn of 2018, we measured abundances and length frequencies of P. atlanticum colonies off the coast of Oregon and estimated their spring grazing impact on the local phytoplankton standing stock. Abundances of P. atlanticum peaked in late winter (0.7 colonies m−3), dropped off in spring (0.42 colonies m−3), and declined to near-absent in early autumn (0.07 colonies m−3). We observed a doubling in the median size of P. atlanticum colonies from late winter to spring, followed by a decline in size in early autumn. With their high individual colony gut pigment contents and bloom densities, the overall spring grazing impact of P. atlanticum was substantial, reaching a maximum of 22% of the available phytoplankton standing stock.

中文翻译：

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Pyrosoma atlanticum 范围扩大对北加州海流浮游植物常备种群的影响

摘要 恰逢 2014 年的海洋热浪和 2016 年的强厄尔尼诺现象，热带-温带远洋殖民地被囊类 Pyrosoma atlanticum 的大量繁殖扩展到北加州洋流 (NCC)。鉴于在 NCC 中观察到的 P. atlanticum 群落密度高，以及它们具有高放牧率的潜力，我们假设该物种可能对东北太平洋的浮游植物存量产生重大负面影响。在 2018 年的冬末、春季和初秋，我们测量了俄勒冈州海岸外大西洋大西洋藻群的丰度和长度频率，并估计了它们春季放牧对当地浮游植物存量的影响。P. atlanticum 的丰度在冬末达到顶峰（0.7 个菌落 m-3），在春季下降（0.42 个菌落 m-3），并在初秋下降到几乎不存在（0.07 个菌落 m-3）。我们观察到从冬末到春季 P. atlanticum 菌落的中位数大小增加了一倍，随后在初秋大小下降。由于个体菌落肠道色素含量高和开花密度高，大西洋对虾的整体春季放牧影响很大，最多可达现有浮游植物存量的 22%。