Large river estuaries experience multiple anthropogenic stressors. Understanding plankton community dynamics in these estuaries provides insights into the patterns of natural variability and effects of human activity. We undertook a 2-year study in the Columbia River Estuary to assess the potential impacts of abiotic and biotic factors on planktonic community structure over multiple time scales. We measured microplankton and zooplankton abundance, biomass and composition monthly, concurrent with measurements of chlorophyll a, nutrient concentrations, temperature and salinity, from a dock in the lower estuary. We then statistically assessed the associations among the abundances of planktonic groups and environmental and biological factors. During the late spring high flow period of both years, the lower estuary was dominated by freshwater and low salinity-adapted planktonic taxa, and zooplankton grazers were more strongly associated with the autotroph-dominated microplankton assemblage than abiotic factors. During the early winter period of higher salinity and lower flow, nutrient (P) availability exerted a strong influence on microplankton taxa, while only temperature and upwelling strength were associated with the zooplankton assemblage. Our results indicate that the relative influence of biotic (grazers) and abiotic (salinity, flow, nutrients and upwelling) factors varies seasonally and inter-annually, and among different size classes in the estuarine food web.

中文翻译：

---

在大型温带河口，浮游生物组合的生物力和非生物力受到季节和大小等级的影响而变化

大河口会遇到多种人为压力源。了解这些河口的浮游生物群落动态，可以洞悉自然变异的形式和人类活动的影响。我们在哥伦比亚河河口进行了为期两年的研究，以评估非生物和生物因子在多个时间尺度上对浮游生物群落结构的潜在影响。我们每月在较低河口的一个码头上测量浮游植物和浮游动物的丰度，生物量和组成，同时测量叶绿素a，养分浓度，温度和盐度。然后，我们对浮游生物的丰富度与环境和生物因素之间的关联性进行了统计评估。在这两年的春末高流量时期，下游河口以淡水和低盐度适应的浮游生物类群为主，与非生物因素相比，浮游生物放牧者与自养生物为主的微浮游生物的联系更紧密。在较高盐度和较低流量的冬季初冬，养分（P）的利用对浮游生物类群有很大的影响，而只有温度和上升强度与浮游动物的组合有关。我们的结果表明，生物因素（放牧者）和非生物因素（盐度，流量，养分和上升流）的相对影响在季节和年际以及河口食物网中的不同大小类别之间有所不同。在较高盐度和较低流量的冬季初冬，养分（P）的利用对浮游生物类群有很大的影响，而只有温度和上升强度与浮游动物的组合有关。我们的结果表明，生物因素（放牧者）和非生物因素（盐度，流量，养分和上升流）的相对影响在季节和年际以及河口食物网中的不同大小类别之间有所不同。在较高盐度和较低流量的冬季初冬，养分（P）的利用对浮游生物类群有很大的影响，而只有温度和上升强度与浮游动物的组合有关。我们的结果表明，生物因素（放牧者）和非生物因素（盐度，流量，养分和上升流）的相对影响在季节和年际以及河口食物网中的不同大小类别之间有所不同。