Interactions between members of the microbial loop in an estuary dominated by microzooplankton grazing, Mobile Bay and Shelf, 2009-2011.

Quantifying the linkages between primary production and higher trophic levels is necessary to understand why particular regions can support high fisheries production. Modified dilution experiments were employed to characterize microbial communities in surface waters at four sites from within a bay to the shelf in the northern Gulf of Mexico (nGOM). Inshore surface waters were more variable than shelf surface waters due to the strong influence of river discharge. Phytoplankton (Chl a) and prokaryote biomass were both significantly higher inshore than on the shelf, with phytoplankton significantly higher than prokaryotes inshore. Virus and heterotrophic nanoflagellate abundances, however, did not differ between inshore and shelf waters. Samples were amended with nutrients (N + P) to examine the impact of nutrient limitation. Prokaryotes were nutrient limited in 14 (28%) of the experiments, while phytoplankton were nutrient limitated in 26 (52%) of the experiments. When phytoplankton were nutrient limited, prokaryote growth rates were significantly altered. A similar impact on phytoplankton growth rates occurred when prokaryotes were nutrient limited, suggesting that the two groups are in competition for resources. Grazing was detected in the majority of experiments, while viral lysis was only detected in 24% of phytoplankton and 12% of prokaryote experiments. Growth and grazing rates for both phytoplankton and prokaryotes were tightly coupled inshore and on the shelf, with significantly more phytoplankton and prokaryotes grazed inshore (average = 106% and 75%, respectively) than on the shelf (average = 55% and 57%). These findings indicate that surface waters across the estuary are highly productive, with microzooplankton grazing transferring the majority of the microbial production to higher trophic levels. Permission to access these data must be given by Dr. Alice Ortmann of the Dauphin Island Sea Lab. Acknowledgment of the Dauphin Island Sea Lab (DISL), Fisheries Oceanography of Coastal Alabama (FOCAL) program, and the Alabama Department of Conservation and Natural Resources is required in products developed from these data, and such acknowledgment as is standard for citation and legal practices for data source is expected by users of these data. Users should be aware that comparison with other data sets for the same area from other time periods may be inaccurate due to inconsistencies resulting from changes in mapping conventions, data collection, and computer processes over time. The distributor shall not be liable for improper or incorrect use of these data, based on the description of appropriate/inappropriate uses described in the metadata document. These data are not legal documents and are not to be used as such.

量化初级生产与更高营养级之间的关联，是理解特定区域何以支撑高渔业生产力的必要前提。本研究采用改良稀释培养实验，对墨西哥湾北部（nGOM）内从海湾内部至陆架的4个站位的表层水体微生物群落进行表征。近岸表层水体因受河流径流的强烈影响，其变化性高于陆架表层水体。浮游植物（叶绿素a，Chl a）与原核生物生物量在近岸区域均显著高于陆架区域，且近岸处浮游植物生物量显著高于原核生物。然而，病毒与异养纳米鞭毛虫的丰度在近岸与陆架水体间并无显著差异。为探究营养限制的影响，研究人员对样品添加了氮（N）与磷（P）营养盐。14组（占比28%）实验中原核生物受到营养限制，而26组（占比52%）实验中浮游植物受到营养限制。当浮游植物受到营养限制时，原核生物的生长速率会发生显著改变；而当原核生物受到营养限制时，浮游植物的生长速率也会出现类似变化，这表明两类生物存在资源竞争关系。多数实验中均可检测到牧食作用，但病毒裂解作用仅在24%的浮游植物实验与12%的原核生物实验中被检出。近岸与陆架区域的浮游植物、原核生物的生长速率与牧食速率均紧密耦合，且近岸区域被牧食的浮游植物与原核生物占比（分别为平均106%与75%）显著高于陆架区域（分别为平均55%与57%）。上述研究结果表明，该河口区域的表层水体生产力极高，微型浮游动物的牧食作用将绝大多数微生物生产的有机质传递至更高营养级。如需获取本数据集的访问权限，须获得多尔芬岛海洋实验室（Dauphin Island Sea Lab）的Alice Ortmann博士许可。基于本数据集开发的研究成果，须注明对多尔芬岛海洋实验室（DISL）、阿拉巴马州沿海渔业海洋学（FOCAL）项目以及阿拉巴马州保护与自然资源部的致谢；数据集使用者亦需遵循学术引用与数据源相关法律规范的标准致谢要求。使用者需注意，由于随时间推移制图规范、数据采集与计算机处理流程的变化可能导致数据不一致，将本数据集与其他时期同一区域的数据集进行对比可能存在误差。数据集分发方不对因使用者未遵循元数据文档中关于合理/不合理使用的说明而导致的不当或错误使用承担责任。本数据集不属于法律文件，不得作为法律文件使用。