Herbivorous consumption of primary production is a key transformation in global biogeochemical cycles, directing matter and energy either to higher trophic levels, export production, or remineralization. Grazing by microzooplankton is often poorly constrained, particularly in dynamic coastal systems. Temperate coastal areas are seasonally and spatially variable, which presents both challenges and opportunities to identify patterns and drivers of grazing pressure. Here we report on two winter and one summer week‐long cruises (2018–2019), as part of the new Northeast U.S. Shelf Long‐Term Ecological Research program. During both seasons, coastal waters were colder and fresher, and had higher phytoplankton biomass than waters at the shelf break. The phytoplankton community was dominated by large cells in winter and by small cells in summer. Phytoplankton growth rates ranged from < 0.5 d⁻¹ in winter and up to 1.4 d⁻¹ in summer and were strongly correlated to temperature, to light availability, and to phytoplankton community size‐structure. Grazing rates were not correlated with total chlorophyll a, which points to other biological drivers, including species composition in predator‐prey interactions at the first trophic level. The percentage of primary production consumed (%PP) indicated higher trophic transfer in winter (%PP > 50%) than during summer (%PP < 20%), highlighting seasonal shifts in planktonic food web structure and function. These results imply that predictable shifts in environmental conditions can be linked to ecosystem shifts in net primary production. Hierarchies of variability, from localized to interannual and long‐term climate driven, can be understood within the context of sustained measurements of ecosystem properties and function.

中文翻译：

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美国东北大陆架浮游食物网结构和功能的季节性变化

初级生产中的草食消费是全球生物地球化学循环中的一个关键转变，它将物质和能量引导到更高的营养水平，出口生产或再矿化。微带浮游动物的放牧通常很难控制，特别是在沿海动态系统中。温带沿海地区在季节和空间上都是可变的，这既带来了挑战，也带来了确定放牧压力的模式和驱动因素的机会。在这里，我们报告了两个冬季和一个夏季一周的巡游（2018-2019年），这是新的美国东北部陆架长期生态研究计划的一部分。在两个季节中，沿海水都比货架期水更冷，更新鲜，浮游植物的生物量也更高。浮游植物群落在冬季以大细胞为主，在夏季以小细胞为主。^-1在冬季和高达1.4 d ^-1在夏季，是紧密相关的温度，光的可用性，并浮游植物群落的大小结构。放牧率与总叶绿素a无关 ，这指出了其他生物驱动因素，包括在第一营养级的捕食者与猎物相互作用中的物种组成。消耗的初级生产百分比（％PP）表明，冬季的营养转移（％PP> 50％）比夏季的营养转移高（％PP <20％），这突出了浮游食物网结构和功能的季节性变化。这些结果表明，可预见的环境条件变化可以与净初级生产中的生态系统变化联系在一起。在对生态系统特性和功能进行持续测量的背景下，可以理解从局部性到年际性和长期性气候驱动的变异性层次。