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

2012年秋季，奥兰治县卫生区(OCSD)将在约4周的时间内，将约1.5亿加仑/天的二级处理污水转移到近岸(离岸1英里)的排污管道。几十年来，还没有进行过如此大规模的排放。计划中的改道预计将产生一股浮力的表面羽流，将蔓延到沿海地区的大部分地区。由于OCSD计划对排放进行“超级氯化”，然后对排放进行脱氯处理，因此羽流的影响应该主要是添加营养物质，而不是直接添加完整的微生物种群。私人投资机构建议通过对烟羽的研究来解决两个广泛的问题。首先，当营养物质长时间排放到表层海洋时，浮游植物在生态和生理上会发生什么？其次，通过部署多种技术，在生态相关的空间和时间尺度上识别生物反应的物理/化学驱动因素，能否对这种动态和变化的环境进行采样？他们将检验两个假设：H1：持续向表层海洋排放营养物质会导致以甲藻为主的水华，从而抑制或停止甲藻的垂直迁移，并推动向净异养的转变。H2：水华最初将导致一个强大的局部二氧化碳汇，随着异养的发展逐渐发展为一个强大的源。这项研究有望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，并将说明持续向沿海浅水地点排放营养物质的短期生物地球化学和生态后果。计划中的改道提供了一个前所未有的机会，在几周的时间里研究自然环境下的生态生理反应，包括生物、化学和物理的相互作用，它将有助于对沿海海洋人为营养物质负荷的基本了解。本科生和研究生的教育和培训将通过积极参与实验室、现场和数据合成活动来进一步推进，这些活动涉及学术、政府和行业合作伙伴。

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.