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首页> 外文期刊>Continental Shelf Research: A Companion Journal to Deep-Sea Research and Progress in Oceanography >Interacting physical, chemical and biological forcing of phytoplankton thin-layer variability in Monterey Bay, California
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Interacting physical, chemical and biological forcing of phytoplankton thin-layer variability in Monterey Bay, California

机译：加利福尼亚蒙特雷湾浮游植物薄层变异的相互作用的物理，化学和生物强迫

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摘要

During the 2005 Layered Organization in the Coastal Ocean (LOCO) field program in Monterey Bay, California, we integrated intensive water column surveys by an autonomous underwater vehicle (AUV) with satellite and mooring data to examine the spatiotemporal scales and processes of phytoplankton thin-layer development. Surveying inner to outer shelf waters repeatedly between August 18 and September 6, the AUV acquired 6841 profiles. By the criteria: [(1) thickness r3 m at the full-width half-maximum, (2) peak chlorophyll at least twice the local background concentrations, and (3) a corresponding peak in optical backscattering], thin layers were detected in 3978 (58%) of the profiles. Average layer thickness was 1.4 m, and average intensity was 13.5 mg l1 above (3.2x) background. Thin layers were observed at depths between 2.6 and 17.6 m, and their depths showed diurnal vertical migration of the layer phytoplankton populations. Horizontal scales of thin-layer patches ranged from o100 m to410,000 m. A thin-layer index (TLI), computed from layer frequency, intensity and thinness, was highest in mid-shelf waters, coincident with a frontal zone between bay waters and an intrusion of low-salinity offshore waters. Satellite observations showed locally enhanced chlorophyll concentrations along the front, and in situ observations indicated that phytoplankton may have been affected by locally enhanced nutrient supply in the front and concentration of motile populations in a convergence zone. Minimum TLI was furthest offshore, in the area most affected by the intrusion of offshore, low-chlorophyll waters. Average thin-layer intensity doubled during August 25–29, in parallel with warming at the surface and cooling within and below the thermocline. During this apparent bloom of thin-layer populations, density oscillations in the diurnal frequency band increased by an order of magnitude at the shelfbreak and in near-bottom waters of the inner shelf, indicating the role of internal tidal pumping from Monterey Canyon onto the shelf. This nutrient transport process was mapped by the AUV. Peak TLI was observed on August 29 during a nighttime survey, when phytoplankton were concentrated in the nutricline. Empirical orthogonal function decomposition of the thin-layer particle size distribution data from this survey showed that throughout the inner to outer shelf survey domain, the layers were dominated by phytoplankton having a cross-section of 50 mm. This is consistent with the size of abundant Akashiwo sanguinea cells observed microscopically in water samples. During a subsequent and stronger intrusion of low-salinity offshore waters, spatially-averaged vertical density stratification decreased by 4 50%, and phytoplankton thin layers disappeared almost completely from the AUV survey domain.
机译：在2005年加利福尼亚州蒙特雷湾的沿海海洋分层组织（LOCO）实地计划中，我们将自动水下航行器（AUV）的密集水柱调查与卫星和系泊数据进行了整合，以检查浮游植物稀薄的时空尺度和过程。层开发。在8月18日至9月6日之间，AUV重复测量了内陆至外陆架水域，获得了6841份剖面图。根据以下标准：[（1）全宽度半最大值处的厚度r3 m，（2）叶绿素的峰至少是局部背景浓度的两倍，（3）光学反向散射的相应峰]，在3978个（58％）。平均层厚为1.4 m，平均强度为高于（3.2x）背景的13.5 mg l1。在2.6至17.6 m的深度处观察到薄层，其深度显示出该层浮游植物种群的昼夜垂直迁移。薄层斑块的水平尺度范围从o100 m到410,000 m。根据层的频率，强度和稀薄度计算得出的薄层指数（TLI）在架子中水域中最高，与海湾水域之间的前缘区域和低盐度近海水域的入侵相吻合。卫星观测结果表明，沿前部的叶绿素浓度局部升高，而原位观测表明，浮游植物可能受到前部局部营养物供应量增加和汇聚区运动种群浓度的影响。在离岸低叶绿素水入侵最受影响的地区，最低TLI在离岸最远。在8月25日至29日期间，平均薄层强度增加了一倍，与此同时，地表变暖以及温跃层内部和下方的冷却也同时出现。在这一薄层种群的明显开花期间，在架子破裂和内架子的近底部水域，昼夜频带内的密度振荡增加了一个数量级，表明内部潮汐从蒙特利峡谷泵送到架子的作用。营养素的运输过程由AUV绘制。在夜间调查中，8月29日观测到TLI峰值，当时浮游植物集中在营养物质中。来自该调查的薄层粒度分布数据的经验正交函数分解表明，在整个内到外层架调查域中，各层均以浮游植物为主，其横截面积为50 mm。这与在水样中通过显微镜观察到的丰富的赤潮血红细胞的大小一致。随后，低盐度近海水域的入侵更加强烈，空间平均垂直密度分层降低了4 50％，浮游植物的薄层在AUV调查范围内几乎完全消失。

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