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首页> 外文期刊>Marine ecology progress series >Structure-dependent, protistan grazing and its implication for the formation, maintenance and decline of plankton patches
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Structure-dependent, protistan grazing and its implication for the formation, maintenance and decline of plankton patches

机译：依赖结构的原生动物放牧及其对浮游生物斑块形成，维持和衰退的影响

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Plankton distributions are frequently patchy and phytoplankton patches have long been suggested as important resources in otherwise nutritionally dilute environments. The present study confirms this hypothesis empirically in a coastal fjord with naturally forming phytoplankton patches and examines the implications for plankton distributions, abundance and rates of patch formation, maintenance and decline. Phytoplankton patches were identified using a CTD mounted fluorometer and sampled with a horizontally mounted 21 Niskin bottle in 3 separate field seasons in summer 2007 and 2008 and spring 2009. We quantified chl a and macronutrient concentrations as well as phytoplankton growth and zooplankton (<200 μm) grazing rates. Average phytoplankton growth was equal inside and outside of patches (0.34 ± 0.07 d~(-1)) and there was no indication of nutrient limitation to phytoplankton growth. Average grazing rate inside patches (0.25 ± 0.03 d~(-1)) was significantly higher than outside of patches (0.09 ± 0.03 d~(-1)). Grazing pressure was not simply a function of prey availability; there was no significant relationship between grazing rate and initial chl a concentration. Protistan grazing consumed on average 65% of primary production within and 26% outside of patches. Model predictions of population dynamics suggest that protistan grazing focused within patches and more rapid phytoplankton accumulation outside of patches eroded layer structures within hours to days. Formation of plankton patches due to phytoplankton growth was not supported by the data. Averaging rates, irrespective of phytoplankton distribution, greatly overestimated layer persistence and minimally underestimated primary production and its availability to higher trophic levels. These results emphasize empirically the importance of predator-prey interactions to the ubiquitous phenomenon of plankton patchiness and ultimately microbial food web dynamics.
机译：浮游生物的分布通常是不规则的，长期以来人们一直建议将浮游植物斑块作为营养稀薄环境中的重要资源。本研究在具有天然形成的浮游植物斑块的沿海峡湾中凭经验证实了这一假设，并研究了对浮游生物分布，斑块形成的丰度和速率，维持和下降的影响。使用安装在CTD上的荧光计确定浮游植物斑块，并在2007年夏季和2008年以及2009年春季的3个单独的田间季节中，使用水平安装的21 Niskin瓶进行采样。我们定量了chl a和大量营养素的浓度以及浮游植物的生长和浮游动物（<200μm ）放牧率。斑块内外的平均浮游植物生长相等（0.34±0.07 d〜（-1）），没有营养限制浮游植物生长的迹象。斑块内的平均放牧率（0.25±0.03 d〜（-1））明显高于斑块外的平均放牧率（0.09±0.03 d〜（-1））。放牧压力不仅仅是捕食能力的函数；放牧率与初始chl a浓度之间没有显着关系。原生动物放牧平均消耗了斑块内65％的初级产品，而斑马外26％。对种群动态的模型预测表明，原生动物放牧集中在斑块内，而在斑块外，浮游植物的更快速积累在数小时至数天内侵蚀了层结构。该数据不支持由于浮游植物生长而形成的浮游生物斑块。不论浮游植物的分布如何，平均速率都大大高估了水层的持久性，并将初级产量及其在较高营养级别的可用性低估到最低程度。这些结果从经验上强调了捕食者与猎物之间的相互作用对无处不在的浮游生物斑块现象以及最终微生物食物网动力学的重要性。

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