Collaborative Research: Multiple Stressors in the Estuarine Environment: What drives changes in the Carbon Dioxide system?

要了解河口生态系统对人为影响的脆弱性，需要对河口碳酸盐系统变化的动态驱动因素进行定量评估。河口目前正经历着多种环境压力，这些压力对其碳酸盐化学有重大影响，这使得这一评估成为一个重大挑战。虽然营养物质径流变化(即富营养化和低氧)的影响在许多河口已经被长期研究，但对全球变化对这些系统的影响的关注要少得多。在这项研究中，一组现场科学家和模型师将试图通过使用在适当的空间和时间尺度上的二氧化碳系统观测校准的数值模型，将美国主要河口的自然年际变化与当地人为变化(例如，营养物质输入、淡水末端成员特征的变化)和全球变化(大气温度、大气二氧化碳和海平面的增加)的影响区分开来。如果成功，这将是第一项定量区分局部和全球人为影响河口二氧化碳系统的研究。这一结果预计将对切萨皮克湾的管理产生重要影响，因为一旦隔离，当地人为应激源对系统的影响可能会通过在区域范围内实施适当的环境政策来缓解。在这个项目中，研究人员将研究切萨皮克湾非原始河口二氧化碳系统的日变化、季节变化和年际变化，使用传统的船上采样(溶解无机碳和碱度)和新的高频自主仪器(用于观测pH和二氧化碳分压)来评估极端事件(如热带风暴和北极星对碳酸盐化学的影响)的影响。这些高质量的观测结果将对30年的PH值和碱度水质监测时间序列的不确定性进行严格评估。该小组将使用河口-碳-生物地球化学模型，通过新的长期观测对其进行评估和校准。敏感性实验将被用来理清过去30年来对河口二氧化碳系统的多重影响，包括大气温度和二氧化碳增加，海平面上升，营养物质径流增加导致的富营养化，以及河流末端碳酸盐特征的变化。

Understanding the vulnerability of estuarine ecosystems to anthropogenic impacts requires a quantitative assessment of the dynamic drivers of change to the estuarine carbonate system. Estuaries are currently experiencing multiple environmental stressors that have significant impacts on their carbonate chemistry, making this assessment a major challenge. Although the effects of changes in nutrient run-off (i.e. eutrophication and hypoxia) have been long-studied in many estuaries, much less attention has been given to the impacts of global change on these systems. In this study, a team of field scientists and modelers will attempt to distinguish natural interannual variability in a major US estuary from the impacts of local anthropogenic changes (e.g., nutrient inputs, changing freshwater end member characteristics) and global change (increases in atmospheric temperature, atmospheric carbon dioxide, and sea level), by using numerical models calibrated with CO2-system observations at appropriate spatial and temporal scales. If successful, this will be the first study to quantitatively distinguish between local and global anthropogenic impacts on the CO2 system in an estuary. The results are expected to have important implications for management of Chesapeake Bay because the impact of local anthropogenic stressors on the system, once isolated, may be mitigated by appropriate environmental policy implemented at the regional scale. Two of the PIs have a strong history of proven relationships with Chesapeake Bay managers and policy makers, which will insure direct infusion of these scientific results into ongoing management decisions.In this project researchers will study the diurnal, seasonal, and interannual variability of the CO2 system in the Chesapeake Bay, a non-pristine estuary, using a combination of conventional shipboard sampling (of dissolved inorganic carbon, and alkalinity) and new high-frequency autonomous instrumentation (for observations of pH and CO2 partial pressure) to assess the impact of extreme events, like tropical storms and nor?easters on carbonate chemistry. These high-quality observations will afford a rigorous assessment of the uncertainty associated with a 30-year water-quality monitoring time series of pH and alkalinity. The team will use an estuarine-carbon-biogeochemical model evaluated and calibrated with the new and long-term observations. Sensitivity experiments will be applied to disentangle multiple impacts on the CO2 system in the estuary over the last 30 years, including increased atmospheric temperature and CO2, sea-level rise, eutrophication due to increases in nutrient run-off, and changing carbonate characteristics of riverine end-members.