ABSTRACT: River plumes discharging into continental shelf waters have the potential to influence the distributions, predator-prey relationships, and thus survival of nearshore marine fish larvae, but few studies have been able to characterize the plume environment at sufficiently fine scales to resolve the underlying mechanisms. We used a high-resolution plankton imaging system and a sparse convolutional neural network to automate image classification of larval fishes, their planktonic prey (calanoid copepods), and gelatinous planktonic predators (ctenophores, hydromedusae, and siphonophores) over broad spatial scales (km) and multiple pulses of estuarine water exiting Mobile Bay (Alabama, USA) into the northern Gulf of Mexico from 9-11 April 2016. Fine-scale (1 m) plankton distributions were examined to analyze predator-prey relationships across 3 distinct plume regimes that varied by degree of wind-forcing and mixing rates. In calm wind conditions, the water column was highly stratified, and fish larvae and zooplankton were observed aggregating in a region of river plume-derived hydrodynamic convergence. As winds strengthened, the water column was subjected to downwelling and highly turbulent conditions, and there was decreasing spatial overlap between larval fishes and their zooplankton prey and predators. Our results indicate that high-discharge plume regimes characterized by strong wind-forcing and turbulence can rapidly shift the physical and trophic environments from favorable to unfavorable for fish larvae. Multiple pathways for both nearshore retention and advective dispersal of fish larvae were also identified. Documenting this variability is a first step toward understanding how high discharge events and physical forcing can affect fisheries production in river-dominated coastal ecosystems worldwide.

中文翻译：

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沿海河流为主的生态系统中的小规模幼体鱼分布和捕食者与猎物的动态

摘要：排入大陆架水域的河羽有可能影响其分布，捕食者与被捕食的关系，从而影响近岸海鱼幼虫的生存，但是很少有研究能够以足够精细的尺度表征羽状环境以解决潜在的潜在问题。机制。我们使用高分辨率的浮游生物成像系统和稀疏卷积神经网络对幼虫鱼，其浮游猎物（类pe足类）和凝胶状浮游捕食者（盲足类，水med类和虹吸类）的图像分类进行自动化以及从2016年4月9日至11日从美国莫拉贝湾（Mobile Bay）进入美国北部墨西哥湾的河口水的多个脉冲。检查了小规模（1 m）浮游生物分布，以分析3种不同的羽流状态下的捕食者与猎物之间的关系，这些关系随风力和混合速率的变化而变化。在风平和的条件下，水柱高度分层，并且观察到鱼幼虫和浮游动物聚集在源自河羽的水动力收敛区域。随着风的增强，水柱处于下降流和高度湍流的条件下，幼体鱼及其浮游动物和捕食者之间的空间重叠减少。我们的结果表明，以强风和湍流为特征的高排放羽流状态可以使鱼体的物理和营养环境从有利状态迅速转变为不利状态。还确定了鱼幼体近岸滞留和对流扩散的多种途径。记录这种变化是了解高排放事件和自然强迫如何影响全球以河流为主导的沿海生态系统中渔业生产的第一步。