Collaborative Research: RAPID: Assessing the Ecophysiological and Biogeochemical Response to Deliberate Nutrient Loading in the Southern California Bight

2012年秋季，奥兰治县环卫区（OCSD）将在约4周的时间内，将约1.5亿加仑/天的二级处理废水转移到近岸（离岸1英里）的排水管中。几十年来从未发生过如此大规模的排放。计划中的改道预计会在海面上形成浮力羽流，扩散到大部分沿海地区。由于OCSD计划对污水进行“超氯处理”，然后再进行脱氯处理，因此污水羽流的影响应该主要是增加营养物质，而不是直接增加完整的微生物种群。pi建议通过对羽流的研究来解决两个广泛的问题。首先，当营养物长时间排放到海洋表面时，浮游植物群落在生态和生理上发生了什么变化？其次，这种动态和变化的环境是否可以通过部署多种技术来确定生态相关空间和时间尺度上生物反应的物理/化学驱动因素来采样？他们将测试两个假设：1：持续向海洋表面排放营养物质导致鞭毛藻为主的水华，从而抑制或停止鞭毛藻的垂直迁移，并推动向净异养的转变。H2：水华最初会在当地形成一个强大的二氧化碳汇，随着异养的发展，这个汇逐渐发展成一个强大的二氧化碳源。该研究预计将提供自养和异养群落内部和之间相互作用的时间演变图景，并将说明持续向浅海岸区排放营养物的短期生物地球化学和生态后果。计划中的调水为研究自然环境中数周内的生态生理反应提供了前所未有的机会，包括生物、化学和物理的相互作用，并将有助于对沿海海洋人为营养负荷的基本了解。本科和研究生的教育和培训将通过积极参与涉及学术、政府和行业合作伙伴的实验室、现场和数据综合活动来进一步推进。

In autumn 2012, Orange County Sanitation District (OCSD) will divert ~150 million gallons/day of secondarily-treated effluent to a nearshore (1 mile offshore) outfall pipe over a period of ~4 weeks. No discharges of this magnitude have been conducted in decades. The planned diversion is expected to create a buoyant surface plume that will spread over much of the coastal region. Because OCSD plans to "super-chlorinate" and then dechlorinate the discharge, the effect of the plume should be predominantly a nutrient addition rather than direct addition of intact microbial populations. The PIs propose to address two broad questions through a study of the plume. First, what happens ecologically and physiologically to the phytoplankton assemblage when nutrients are discharged in the surface ocean for extended periods of time? Second, can this dynamic and shifting environment be sampled by deploying multiple technologies to identify the physical/chemical drivers of the biological response at ecologically relevant space and time scales? They will test two hypotheses: H1: Continual discharge of nutrients to the surface ocean results in a dinoflagellate-dominated bloom which leads to dampening or cessation of vertical migration of the dinoflagellates and drives a shift to net heterotrophy. H2: The bloom will initially result in a strong local sink for carbon dioxide which gradually develops into a strong source as heterotrophy develops.The study is expected to provide a time-evolving picture of interactions within and between autotrophic and heterotrophic communities and will illustrate the short-term biogeochemical and ecological consequences of sustained nutrient discharge to a shallow coastal site. The planned diversion provides an unprecedented opportunity to study the ecophysiological response in a natural setting over a period of weeks, including the interaction of biology, chemistry, and physics, and it will contribute to basic understanding of anthropogenic nutrient loading to the coastal ocean. Undergraduate and graduate education and training will be furthered through active participation in lab, field, and data synthesis activities involving academic, government, and industry partners.