L. Linacre , R. Durazo , V. Camacho-Ibar , U. Mirabal-Gómez , J.A. Velásquez-Aristizábal , C. Sánchez-Robles , J.R. Lara-Lara , C. Bazán-Guzmán
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This study addresses the temporal variability of microbial community biomass in two oceanic zones: the west-central (Perdido) and southern (Coatzacoalcos) areas of the Gulf of Mexico. During three seasonally contrasting periods (<em>nortes</em>, <em>rainy</em>, and <em>dry</em> seasons), seawater samples were collected from the euphotic zone in both regions to estimate the carbon biomass of different pico- (<2–3 µm), nano-, and microplankton groups (>3–200 µm). Carbon biomass assessments for the microbial groups were based on their abundance and carbon conversion factors. Overall, we found a significant contribution of pico-prokaryotic components (heterotrophic bacteria, <em>Prochloroccocus</em>, and <em>Synechoccocus</em>) to the total microbial carbon stock of the euphotic zone (84–89 % global estimates). The finding suggests these microorganisms are key functional groups that drive carbon production and fate in the Gulf of Mexico ecosystem. Pico-cyanobacteria, especially <em>Prochloroccocus</em>, were the dominant primary producers (68–82 % total autotrophic carbon), mainly in the upper layer of the oligotrophic euphotic zone. This vertical pattern implies that the deep chlorophyll-<em>a</em> maximum (DCM) depth level was unrelated to a net increase in phytoplankton biomass in the three study periods. The distribution of microbial carbon biomass exhibited striking differences associated with winter mixing (the <em>nortes</em> season), high river discharge accompanied by cross-shelf transport (the <em>rainy</em> season), and the dynamics of mesoscale structures. Ecological aspects, such as the habitat preference of the organisms and the seasonal complementary development of mixotrophic and heterotrophic grazers and their prey, were also essential drivers in regulating the microbial carbon pool of both oceanic regions. 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引用次数: 0
摘要
浮游微生物群落是浮游生态系统不可分割的一部分。浮游微生物群落拥有重要的功能群,在公海生态系统的有机碳生产、释放、吸收和降解过程中发挥着至关重要的作用。鉴于其重要性,我们迫切需要对碳生物量进行估算,尤其是在寡营养区域,以提供并加强我们对生物碳库的了解。它们还有助于验证生物地球化学模型,该模型描述了这些广阔的海洋生态系统在全球碳循环中的功能。本研究探讨了墨西哥湾中西部(佩尔迪多)和南部(科萨科尔科斯)两个海区微生物群落生物量的时间变异性。在三个季节对比鲜明的时期(北季、雨季和旱季),从这两个地区的透光层采集海水样本,估算不同皮米级(2-3 微米)、纳米级和微浮游生物群(3-200 微米)的碳生物量。微生物组的碳生物量评估基于其丰度和碳转换因子。总体而言,我们发现微微原核生物(异养细菌、原链球菌和 Synechoccocus)对透光层微生物总碳储量的贡献很大(全球估计值为 84-89%)。这一发现表明,这些微生物是驱动墨西哥湾生态系统碳生产和碳归宿的关键功能群。微囊藻类,尤其是原绿球藻,是主要的初级生产者(占自养碳总量的 68-82%),主要分布在低营养透光层的上层。这种垂直模式意味着,在三个研究时段,深层叶绿素 a 最大值(DCM)深度与浮游植物生物量的净增长无关。微生物碳生物量的分布呈现出显著的差异,这与冬季混合(北季)、伴随着跨大陆运输的高河水排放量(雨季)以及中尺度结构的动态有关。生态学方面的因素,如生物的栖息地偏好以及混养和异养食草动物及其猎物的季节性互补发展,也是调节这两个大洋区域微生物碳库的重要驱动力。本研究进行的微生物碳评估有助于确定和量化参与墨西哥湾公海生态系统生物地球化学碳循环的主要浮游生物功能群。
Drivers of microbial carbon biomass variability in two oceanic regions of the Gulf of Mexico
The microbial plankton community is an integral part of the pelagic ecosystem. It hosts essential functional groups that play a vital role in organic carbon production, release, uptake, and degradation within open-ocean ecosystems. Given its significance, carbon biomass estimates are urgently needed, especially in oligotrophic regions, to provide and enhance our knowledge of biogenic carbon pools. They also aid in validating biogeochemical models that characterize the functioning of these extensive marine ecosystems within the global carbon cycle. This study addresses the temporal variability of microbial community biomass in two oceanic zones: the west-central (Perdido) and southern (Coatzacoalcos) areas of the Gulf of Mexico. During three seasonally contrasting periods (nortes, rainy, and dry seasons), seawater samples were collected from the euphotic zone in both regions to estimate the carbon biomass of different pico- (<2–3 µm), nano-, and microplankton groups (>3–200 µm). Carbon biomass assessments for the microbial groups were based on their abundance and carbon conversion factors. Overall, we found a significant contribution of pico-prokaryotic components (heterotrophic bacteria, Prochloroccocus, and Synechoccocus) to the total microbial carbon stock of the euphotic zone (84–89 % global estimates). The finding suggests these microorganisms are key functional groups that drive carbon production and fate in the Gulf of Mexico ecosystem. Pico-cyanobacteria, especially Prochloroccocus, were the dominant primary producers (68–82 % total autotrophic carbon), mainly in the upper layer of the oligotrophic euphotic zone. This vertical pattern implies that the deep chlorophyll-a maximum (DCM) depth level was unrelated to a net increase in phytoplankton biomass in the three study periods. The distribution of microbial carbon biomass exhibited striking differences associated with winter mixing (the nortes season), high river discharge accompanied by cross-shelf transport (the rainy season), and the dynamics of mesoscale structures. Ecological aspects, such as the habitat preference of the organisms and the seasonal complementary development of mixotrophic and heterotrophic grazers and their prey, were also essential drivers in regulating the microbial carbon pool of both oceanic regions. The microbial carbon assessments conducted in this study contribute to identifying and quantifying key planktonic functional groups involved in the biogeochemical carbon cycle in the Gulf of Mexico open-ocean ecosystem.
期刊介绍:
Progress in Oceanography publishes the longer, more comprehensive papers that most oceanographers feel are necessary, on occasion, to do justice to their work. Contributions are generally either a review of an aspect of oceanography or a treatise on an expanding oceanographic subject. The articles cover the entire spectrum of disciplines within the science of oceanography. Occasionally volumes are devoted to collections of papers and conference proceedings of exceptional interest. Essential reading for all oceanographers.