High-resolution sensing of nitrate in Monterey Bay and surrounding waters

硝酸盐是海洋中的一种重要营养物质，维持光合生物对阳光能量的利用。沿着美国西海岸，强风将富含硝酸盐的海水从深海带到阳光照射的海面。这一沿海涌升过程促进了海洋食物网底层的增长和生产力，但也与沿海沿着的低氧条件和有害藻华有关。除了风驱动的沿海岸沿着上升流外，陆地上的硝酸盐径流还可能导致河口有机物过度富集，导致低氧条件和栖息地退化。硝酸盐的传统测量使用化学方法，这些方法耗时，并且将样品的数量限制为可以物理收集在瓶中的数量。光学传感器技术的最新进展使快速收集硝酸盐数据成为可能（每秒一个样本），允许收集更详细的数据。该项目的目的是使硝酸盐的高分辨率传感成为加利福尼亚州蒙特雷湾中心Moss Landing Marine Laboratories（MLML，https://www.mlml.calstate.edu）的标准测量。测量硝酸盐以及其他海洋条件和水质的观测结果将提供一个更完整的画面，了解营养物质的可用性如何在几天和几个月的时间内变化，以及蒙特雷湾和附近河口的小空间尺度。在MLML使用高分辨率硝酸盐传感将为课堂带来先进的技术，并为学生的研究提供新的机会。现代硝酸盐传感技术的使用和校准培训将在课堂上进行，学生将获得独立研究的设备和数据。硝酸盐传感器将支持对有害藻华、海洋酸化的区域影响、可持续水产养殖和河口水质的研究。硝酸盐浓度受到许多物理、生物地球化学和人为过程的影响，包括沿海涌升、内波、光合作用、有氧呼吸、反硝化作用和农业径流。硝酸盐是初级生产力的燃料，这通常也与低氧、富营养化和有害藻类有关。然而，硝酸盐的复杂的空间分布，和广泛的时间尺度的变化，很难用传统的方法来表征。传感器技术的最新进展使人们有可能在短的时间和空间尺度上测量的特征河口和沿海涌升区的硝酸盐浓度的变化。该项目的目标是使硝酸盐的高分辨率传感成为Moss Landing Marine Laboratories（MLML，https://www.mlml.calstate.edu）四个观测平台上的标准测量：1）连续测量地下水特性的海水进水系统，2）56英尺（1.5米）上的垂直剖面玫瑰花形。沿海研究船，3）在同一船上连续测量地表水特性的在航数据采集系统，以及4）可随时部署在任何小船或码头上的便携式在航数据采集系统。这些研究平台已经支持一系列物理、生物和化学传感器，用于蒙特雷湾和周围沃茨的跨学科研究。在四个互补的观测平台上安装硝酸盐传感器将为蒙特雷湾地区的研究人员提供一个坚实的基础，以了解硝酸盐和浮游植物生物量在时间和空间上的变化。

Nitrate is an important nutrient in the ocean that sustains the use of energy from sunlight by photosynthetic organisms. Along the U.S. west coast, strong winds bring water that is rich in nitrate from the deep ocean to the sunlit ocean surface. This coastal upwelling process fuels growth and productivity at the base of the marine food web, but is also linked to low-oxygen conditions and harmful algal blooms along the coast. In addition to wind-driven upwelling along the coast, runoff of nitrate from land can cause excess enrichment of organic matter in estuaries, leading to low-oxygen conditions and habitat degradation. Traditional measurements of nitrate use chemical methods that are time consuming and limit the quantity of samples to those that can be physically collected in bottles. Recent advances in optical sensor technology have made it possible to collect nitrate data rapidly (up to one sample per second), allowing the collection of data with much greater detail. The purpose of this project is to make high-resolution sensing of nitrate a standard measurement at Moss Landing Marine Laboratories (MLML, https://www.mlml.calstate.edu) in central Monterey Bay, CA. Measuring nitrate alongside other observations of ocean conditions and water quality will provide a more complete picture of how nutrient availability changes over the course of days and months, and at small spatial scales down to meters in Monterey Bay and nearby estuaries. The use of high-resolution nitrate sensing at MLML will bring advanced technology into the classroom and provide new opportunities for student research. Training in the use and calibration of modern nitrate sensing technology will take place in the classroom, and students will have access to equipment and data for independent research. The nitrate sensors will support research on harmful algal blooms, regional impacts of ocean acidification, sustainable aquaculture, and estuarine water quality.Nitrate concentrations are influenced by many physical, biogeochemical and anthropogenic processes, including coastal upwelling, internal waves, photosynthesis, aerobic respiration, denitrification, and agricultural runoff. Nitrate fuels primary productivity, which is often also associated with low oxygen, eutrophication and harmful algae. However, the complex spatial distributions of nitrate, and the wide range of time scales of variability, are difficult to characterize with traditional methods. Recent advances in sensor technology have made it possible to measure variability in nitrate concentrations at the short temporal and spatial scales that characterize estuaries and coastal upwelling regions. The goal of this project is to make high-resolution sensing of nitrate a standard measurement on four observing platforms at Moss Landing Marine Laboratories (MLML, https://www.mlml.calstate.edu): 1) a seawater intake system that continuously measures subsurface water properties, 2) a vertically profiling rosette on a 56 ft. coastal research vessel, 3) an underway data acquisition system that continuously measures surface water properties on the same vessel, and 4) a portable underway data acquisition system that can be readily deployed on any small boat or pier. These research platforms already support an array of physical, biological and chemical sensors for interdisciplinary research in Monterey Bay and surrounding waters. Installing nitrate sensors on four complementary observing platforms would provide researchers in the Monterey Bay region with a strong foundation for understanding how nitrate and phytoplankton biomass vary both in time and space.