Geographic Variation of Particle Size Distribution in the Kuroshio Region: Possible Causes in the Upper Water Column
Geographic Variation of Particle Size Distribution in the Kuroshio Region: Possible Causes in the Upper Water Column
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DOI：
10.3389/fmars.2021.768766
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发表时间：
2021-11
期刊：
影响因子：
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通讯作者：
Yosuke Yamada;H. Fukuda;Y. Umezawa;T. Nagata
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文献类型：
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作者：
Yosuke Yamada;H. Fukuda;Y. Umezawa;T. Nagata
海洋中的颗粒大小分布(PSD)是影响碳输出和食物网的一个基本属性；然而，低营养海洋中PSD的变化及其原因并不完全清楚。本文利用激光原位散射法和透射法对西北太平洋黑潮海域表层(0-20 m)11个测站的PSD(尺度范围5.2-119μm)及其相关变量进行了研究，该区域的强流形成了动态的水文和生态条件。根据幂定律模型得出的PSD斜率(-3.2至-4.2)在岸上站较陡，而在近海和低纬度的低营养站较平坦。值得注意的是，随着叶绿素a浓度的增加，坡度往往变得更加陡峭，这与通常观察到的两个变量之间的关系相反，而随着透明胞外聚合物颗粒(TEP)浓度的增加，坡度变得更加平坦。对上述结果的可能解释是纳米浮游植物的局部性存在和TEP促进颗粒聚集。结果支持PSD斜率受多种因素控制的假说，包括浮游植物群落动态和聚集过程。为了确定TEP诱导的颗粒聚集是促进还是抑制碳输出，我们需要更好地了解贫营养海洋中聚集的性质(孔隙度、密度和下沉速度)。
Particle size distribution (PSD) in the ocean is a fundamental property that influences carbon export and food webs; however, PSD variation and its causes in oligotrophic oceans are not entirely clear. Here, we used Laser In-Situ Scattering and Transmissometry to investigate PSD (size range 5.2–119 μm) and related variables at 11 stations in the surface layer (0–20 m) of the Kuroshio region of the western North Pacific, where strong current causes dynamic hydrographic and ecological conditions. PSD slopes (range –3.2 to –4.2), derived from the power law model, were steeper at onshore stations and flatter at oligotrophic stations located offshore and at lower latitudes. Notably, slopes tended to become steeper with increasing chlorophyll a concentration, opposing the generally observed relationship between the two variables, whereas they became flatter with increasing transparent exopolymer particle (TEP) concentration. Possible explanations of the above results are localized occurrence of nanophytoplankton and TEP facilitation of particle aggregation. The results support the hypothesis that PSD slopes are controlled by a multitude of factors, including phytoplankton community dynamics and aggregation processes. To determine whether TEP-induced particle aggregation enhances or suppresses carbon export, we need a better understanding of the nature (porosity, density, and sinking velocity) of aggregates in oligotrophic oceans.