Cross-shelf gradients in phytoplankton community structure, nutrient utilization, and growth rate in the coastal Gulf of Alaska
Cross-shelf gradients in phytoplankton community structure, nutrient utilization, and growth rate in the coastal Gulf of Alaska
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阿拉斯加湾沿岸浮游植物群落结构、养分利用率和生长率的跨陆架梯度
DOI：
10.3354/meps328075
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发表时间：
2006
影响因子：
2.5
通讯作者：
CW Mord
中科院分区：
文献类型：
--
作者：
S. Strom;MB Olson;EL Macri;CW Mord
阿拉斯加湾沿岸(CGOA)支持大量的无脊椎动物、鱼类和海洋哺乳动物。虽然年复一年变化不定，但几十年的鱼产量趋势与诸如太平洋年代际涛动等气候制度相关。风、大量淡水输入和CGOA中复杂的地形在多个时间和空间尺度上创造了高能物理特征。这表明，气候可能通过调节初级生产者的资源与较高的营养水平生产联系在一起。2001年春季和夏季的数据显示，控制CGOA初级生产的因素具有季节性和空间变异性。其中一些最高的生长率(用海水稀释技术估计为>；1.0d-1)是在4月份硅藻水华时测量的。氮素对生长速率的限制早在4月下旬就很明显，而且似乎与春季层结的开始密切相关。夏季浮游植物群落以小型(5微米)细胞为主，根据跨陆架位置的不同，表现出不同程度的氮素限制。然而，我们在阿拉斯加海岸流中观察到了强烈的仲夏硅藻水华，这可能是对一系列上升流事件的反应。强烈的跨陆架梯度支配着浮游植物群落结构和功能的方方面面，包括总生物量、细胞大小、物种组成、养分利用、生长速度和大量营养素的限制程度。这些梯度与溶解铁有效性的跨陆架梯度一致。由于资源限制的类型和浮游植物群落的分类组成在不同的大陆架上有所不同，整个大陆架浮游植物增长率与资源可获得性的逐步回归几乎没有预测能力。气候驱动的资源变化对CGOA初级生产的影响必须结合不同的群落类型、其生产潜力以及决定其范围和稳定性的环境条件来理解。
The coastal Gulf of Alaska (CGOA) supports high abundances of invertebrates, fishes, and marine mammals. While variable from year to year, multi-decade fish production trends have been correlated with climate regimes such as the Pacific Decadal Oscillation. Winds, massive fresh- water inputs, and complex topography in the CGOA create high-energy physical features on multiple time and space scales. This suggests that climate might be linked to higher trophic level production through the regulation of resources for primary producers. Data from spring and summer 2001 revealed seasonal and spatial variability in the factors regulating CGOA primary production. Some of the highest growth rates (>1.0 d -1 , as estimated with the seawater dilution technique) were measured in April diatom blooms. Nitrogen limitation of growth rates was evident as early as late April and appeared to follow closely the onset of spring stratification. The summer phytoplankton community was dominated by small (<5 µm) cells exhibiting varying degrees of nitrogen limitation depending on cross-shelf location. However, we observed an intense mid-summer diatom bloom in the Alaska Coastal Current, perhaps a response to a series of upwelling events. Strong cross-shelf gradients governed every aspect of phytoplankton community structure and function, including overall biomass, cell size, species composition, nutrient utilization, growth rate, and degree of macronutrient limitation. These gradients were consistent with a cross-shelf gradient in dissolved iron availability. Because the type of resource limitation and the taxonomic composition of the phyto- plankton community varied across the shelf, a stepwise regression of whole-shelf phytoplankton growth rates versus resource availability had little predictive power. The effect of climate-driven resource variation on primary production in the CGOA has to be understood in the context of different community types, their production potential, and the environmental conditions that dictate their extent and stability.