Abstract

Microzooplankton play a pivotal role in the energy transfer between lower and upper trophic levels in marine planktonic food webs. While laboratory data suggest that microzooplankton exhibit higher feeding rates during the daytime, evidence from the field is scarce and contradictory. In this study, we first characterized the nano- and microplanktonic communities of the Gullmar Fjord (Sweden) and its environmental conditions during July and August 2017. Then, we explored the grazing impact of microzooplankton on the phytoplankton community of this ecosystem and assessed their diel grazing activity using the dilution technique. Finally, we evaluated the impact of mesozooplankton at natural concentrations during the experiments. Microzooplankton removed 26% of the phytoplankton standing stock and 96% of the primary production daily, while mesozooplankton did not exert a significant impact on microplankton activity. We did not detect significant diel microzooplankton grazing rhythms during the first experimental period; however, during the second part of the study, after an upwelling event, grazing rates were significantly higher during the night. Therefore, the microzooplankton grazing rhythm in natural systems may vary according to the species composition and abundances of both microzooplankton and prey communities.

中文翻译：

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营养丰富的相互作用和生产性的瑞典峡湾微z鱼的diel摄食节律

摘要

微浮游生物在海洋浮游食物网中营养级上下之间的能量传递中起着关键作用。实验室数据表明，微浮游动物在白天表现出较高的摄食率，但该领域的证据很少且相互矛盾。在这项研究中，我们首先表征了Gullmar Fjord（瑞典）的纳米和微浮游生物群落及其在2017年7月和8月的环境条件。然后，我们研究了微浮游藻对该生态系统浮游植物群落的放牧影响并评估了它们的diel使用稀释技术的放牧活动。最后，我们在实验过程中评估了中层浮游动物在自然浓度下的影响。微浮游动物每天清除浮游植物26％的常备种群和96％的初级产品，而中层浮游生物对浮游生物的活动没有显着影响。在第一个实验期间，我们没有发现明显的diel microzooplankton放牧节奏；然而，在研究的第二部分中，在发生上升流事件后，夜间的放牧率明显更高。因此，自然系统中的微浮游动物的放牧节奏可能会根据微浮游动物和猎物群落的物种组成和丰度而变化。