Collaborative Research: Groundwater Discharge, Benthic Coupling and Microalgal Community Structure in as Shallow Coastal Lagoon

合作研究：浅滩泻湖地下水排放、底栖耦合和微藻群落结构

• 批准号: 0961970
• 负责人: William Burnett
• 金额: $ 22.96万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-03-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0961970&HistoricalAwards=false
• 关键词: Collaborative; Research; Groundwater; Discharge; Benthic

Numerous studies over the past few decades have shown that submarine groundwater discharge (SGD) transports significant quantities of nutrients to estuaries and nearshore oceans worldwide. So far, none of the geochemical and hydrological studies of SGD have demonstrated a clear ecological role. At the same time, studies of microalgal community dynamics have suggested, but not verified, that SGD is an important determinant of community structure. We thus have neither thorough SGD investigations with inferences about ecological responses nor detailed observations of microalgae with only an inferred linkage to SGD. Attempting to assess the role of SGD on microalgal dynamics is complicated by two factors. First, discharge occurs through the benthos, which in near-shore waters is the niche inhabited by benthic microalgae. The microphytobenthos (MPB) can be present at densities orders of magnitude higher than the phytoplankton and have repeatedly been shown to alter nutrient efflux. The role of the MPB as a sink for nutrients will depend on their growth rates, which are in turn largely driven by temperature and light availability. The second complicating factor is that SGD can be highly episodic and its nutrient content very variable. The effect of SGD on the phytoplankton assemblage may be due to nutrient delivery and/or to dilution (reduction in competition and grazing pressure) and altered residence times. The time-scales of SGD and community response are difficult to assess by standard sampling methods. This project will to investigate the link between SGD and microalgal dynamics in Little Lagoon, Alabama, a model system for such a study. In contrast to most near-shore environments, it is fully accessible; has no riverine inputs; and is large enough to display ecological diversity (c. 14x 0.75 km) yet small enough to be comprehensively sampled on appropriate temporal and spatial scales. The PIs have previously demonstrated that the lagoon is a hot-spot for toxic blooms of the diatom Pseudo-nitzchia spp that are correlated with discharge from the surficial aquifer. This project will use state-of-the-art techniques to assess variability in SGD, the dependence of benthic nutrient fluxes on MPB abundance and productivity, and the response of the phytoplankton to nutrient enrichment and dilution. The work will integrate multiple temporal and spatial scales and will demonstrate both the relative importance of SGD vs. benthic recycling as a source of nutrients, and the role of SGD in structuring the microalgal community.Broader Impacts: Although this project is geographically restricted, its findings should be far reaching. Groundwater-born nutrient enrichment is now normal where agriculture occurs over porous soils, including in New England, Maryland/Delaware, Florida, Alabama, likely Texas, Yucatan (Mexico), California, Korea, Japan, and the Netherlands etc. The likely dependence of coupling between SGD and phytoplankton composition is likely to be driven by temperature and the frequency/intensity of precipitation, both of which will change in the Northern Hemisphere, according to the IPCC. The phenomenon therefore has wide application. This project will provide training opportunities for three Ph.D. students and the findings will be incorporated into several courses: Physiological Ecology of Microalgae (MacIntyre), Global Biogeochemical Cycles (Mortazavi) and Environmental Radiochemistry (Burnett). Last, this project will build on the PI's active partnership with local citizens, members of the Little Lagoon Preservation Society (LLPS), in bi-weekly monitoring of water quality and microalgal community composition. Members of the PI's lab have presented talks at each of LLPS' quarterly meetings for the past 2 years. These are attended by local stakeholders, local and state political representatives, and members of the press, and have proved to be an effective means for outreach and education on eutrophication, HABs and hypoxia. The relationship has been reported on extensively in the local press and praised as exemplary in an editorial in the region's largest newspaper.

过去几十年的大量研究表明，海底地下水排放（SGD）将大量营养物质输送到世界各地的河口和近岸海洋。迄今为止，SGD 的地球化学和水文研究尚未证明其具有明确的生态作用。与此同时，微藻群落动态研究表明，SGD 是群落结构的重要决定因素，但尚未得到证实。因此，我们既没有对生态反应进行彻底的 SGD 调查，也没有对微藻进行详细观察，仅推断与 SGD 的联系。 试图评估 SGD 对微藻动力学的作用因两个因素而变得复杂。 首先，排放通过底栖生物进行，在近岸水域，底栖生物是底栖微藻栖息的生态位。微型底栖植物 (MPB) 的密度可以比浮游植物高几个数量级，并且已多次被证明可以改变养分流出。 MPB 作为营养物汇的作用将取决于它们的生长速度，而生长速度又在很大程度上受温度和光照的影响。第二个复杂因素是 SGD 可能具有高度偶发性且其营养成分变化很大。 SGD 对浮游植物群落的影响可能是由于营养物输送和/或稀释（减少竞争和放牧压力）和改变停留时间。 SGD 的时间尺度和社区反应很难通过标准抽样方法进行评估。 该项目将研究阿拉巴马州小泻湖的 SGD 和微藻动力学之间的联系，这是此类研究的一个模型系统。与大多数近岸环境相比，它是完全无障碍的；没有河流输入；并且足够大以显示生态多样性（约14x 0.75公里），但又足够小以在适当的时间和空间尺度上进行全面采样。 PI 此前已证明，泻湖是硅藻拟菱形藻有毒水华的热点地区，这与地表含水层的排放有关。 该项目将使用最先进的技术来评估 SGD 的变异性、底栖养分通量对 MPB 丰度和生产力的依赖性，以及浮游植物对养分富集和稀释的响应。这项工作将整合多个时间和空间尺度，并将展示 SGD 与底栖循环作为营养来源的相对重要性，以及 SGD 在构建微藻群落中的作用。 更广泛的影响：尽管该项目受到地理限制，但其调查结果应该具有深远的影响。 在多孔土壤上开展农业活动的地区，地下水产生的养分富集现在已成为常态，包括新英格兰、马里兰/特拉华州、佛罗里达州、阿拉巴马州，可能还包括德克萨斯州、尤卡坦半岛（墨西哥）、加利福尼亚州、韩国、日本和荷兰等。根据 IPCC 的说法，SGD 和浮游植物组成之间的耦合可能是由温度和降水频率/强度驱动的，这两者都会在北半球发生变化。因此，该现象具有广泛的应用。 该项目将为三名博士提供培训机会。研究结果将被纳入几门课程中：微藻生理生态学（MacIntyre）、全球生物地球化学循环（Mortazavi）和环境放射化学（Burnett）。最后，该项目将建立在 PI 与当地居民、小泻湖保护协会 (LLPS) 成员的积极合作伙伴关系的基础上，每两周监测一次水质和微藻群落组成。 PI 实验室的成员在过去两年的每次 LLPS 季度会议上都发表了演讲。这些活动由当地利益相关者、地方和州政治代表以及新闻界人士参加，事实证明，这些活动是针对富营养化、有害细菌和缺氧问题进行宣传和教育的有效手段。当地媒体广泛报道了这种关系，并在该地区最大报纸的一篇社论中被誉为典范。