Collaborative Research: Potential Climate Change Impacts on Algal Dynamics and Biogeochemistry in the Bering Sea

合作研究：气候变化对白令海藻类动力学和生物地球化学的潜在影响

• 批准号: 0327620
• 负责人: Giacomo DiTullio
• 金额: $ 18.65万
• 依托单位: College of Charleston
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-15 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0327620&HistoricalAwards=false
• 关键词: Collaborative; Research; Potential; Climate; Change

Oceanographers recognize the importance of phytoplankton photosynthesis in affecting atmospheric pCO2 and global climate change. Little attention has been given, however, to the opposite question: How will rising anthropogenic pCO2 levels and associated climate changes impact algal community structure and biogeochemistry? Climate-related shifts in phytoplankton assemblages may have profound implications for oceanic feedbacks on the atmosphere, and for human use of marine resources. This is because particular algal groups are largely responsible for crucial processes like vertical carbon export, biogenic calcification, production of climatically active gases like dimethylsulfide (DMS), and for supporting food webs that lead to economically valuable higher trophic levels. Increasing pCO2 and temperature, as well as changes in light and nutrient supplies from a shoaling mixed layer and a stronger thermocline, can drive major switches in algal diversity. These dominance changes include dramatic shifts between siliceous, calcareous, and non-mineralizing phytoplankton, between groups that are major or minor contributors to the biological pump, and between taxa that produce negligible or copious amounts of DMS. The PIs are investigating the potential impacts of pCO2 and climate change on algal community structure and biogeochemistry in the Bering Sea, an area that already exhibits signs of rapid climate regime shifts. Two independent experimental methods are being used: Semi-continuous incubations, to simulate non-equilibrium conditions due to episodic events such as storms, and a unique shipboard chemostat system to simulate quasi-steady state stratified conditions. Experimental treatments include: (1) Ambient pCO2 and temperature conditions, and (2) Elevated pCO2 (750 ppm) and temperature (+ 3o C). Each treatment is subdivided into two mixed layer depth simulations: (1) Ambient nutrient and light conditions and (2) A higher light/lower nutrient treatment to simulate a future decreased MLD. Levels of pCO2 and physical variables chosen were based on current model predictions for the surface ocean by the year 2100. Phytoplankton diversity and carbon and nutrient cycling are being closely followed in these greenhouse ocean simulations, with particular attention to shifts between biogeochemically critical groups like diatoms, coccolithophorids, and Phaeocystis.

海洋学家认识到浮游植物光合作用在影响大气pCO 2和全球气候变化方面的重要性。 然而，很少有人关注相反的问题：人为pCO 2水平的上升和相关的气候变化将如何影响藻类群落结构和生物地球化学？ 浮游植物组合中与气候相关的变化可能对海洋对大气的反馈以及人类对海洋资源的利用产生深远的影响。 这是因为特定的藻类群体在很大程度上负责关键过程，如垂直碳输出，生物钙化，产生气候活性气体，如二甲基硫（DMS），并支持食物网，导致经济上有价值的更高营养水平。 二氧化碳分压和温度的增加，以及变浅的混合层和更强的温跃层带来的光照和营养供应的变化，可以推动藻类多样性的重大转变。 这些优势的变化包括硅质，钙质，和非矿化浮游植物之间的巨大变化，群体之间的主要或次要的贡献者的生物泵，和类群之间产生的DMS量可以忽略不计或丰富。 研究人员正在调查pCO 2和气候变化对白令海藻类群落结构和生物地球化学的潜在影响，白令海已经显示出气候状况迅速变化的迹象。 两个独立的实验方法正在使用：半连续孵育，模拟非平衡条件下，由于偶发事件，如风暴，和一个独特的船上恒化器系统，模拟准稳态分层条件。 实验处理包括：（1）环境pCO 2和温度条件，以及（2）升高的pCO 2（750 ppm）和温度（+3 o C）。 每个处理被细分为两个混合层深度模拟：（1）环境营养和光照条件和（2）较高的光/较低的营养处理，以模拟未来减少MLD。pCO 2水平和物理变量的选择是基于目前的模式预测到2100年的表面海洋。 在这些温室海洋模拟中，浮游植物多样性以及碳和营养物质循环受到密切关注，特别关注硅藻，颗石藻和棕囊藻等地球化学关键群体之间的变化。