An Alternative Framework to Assess Marine Ecosystem Functioning in Shelf Seas (AlterEco)

大陆架海通常不到200米深，可以用环绕大陆块的浅海来描述。由于其可达性，陆架海在商业和经济上都很重要，仅在英国陆架海的石油和天然气开采就价值370亿英镑。尽管只占海洋表面的7%，但陆架海在全球碳循环和海洋生态系统中也发挥着重要作用。陆架海的生产力是公海的3-4倍，估计支持40%以上的碳固存，支持全球90%的鱼类捕捞，为不断增长的沿海人口提供关键的食物来源。然而，陆架海也受到气候驱动和人为压力的影响，这可能对其生物生产力、氧气动态和生态系统功能产生深远影响。造成这一威胁的许多过程与经历垂直分层的区域有关。这个过程发生在陆架海的底层与大气通风的近表层分离时。在温带大陆架海，分层主要发生在太阳能加热超过潮汐和风驱动的混合，产生温暖的表层，导致欧洲西北部大陆架海大面积的季节性分层。从表面的物理脱离和底层生物耗氧量的增加，加上上层海洋分层也支持生产力的提高，可能导致底层氧浓度急剧下降。当氧气水平变得如此之低时，它们被归类为缺氧，这可能对底栖和远洋海洋生物造成问题，并对生态系统功能产生不利影响。AlterEco团队成员发现的北海地区季节性缺氧增加的证据以及全球陆架海和沿海缺氧程度的公认增加，迫切需要增加对氧气的空间和时间测量，并更好地了解导致陆架海底沃茨缺氧的过程。生态系统功能的自然复杂性、气候变化的影响、我们大陆架海不同区域之间的连通性以及来自海洋和大气的大规模外力，严重阻碍了这一需求。目前的方法在解决这一复杂性，由于在观测范围，这需要一个新的战略，观察和监测海洋生态系统和环境states.AlterEco的要求，以解决这一挑战的框架内的一个新的监测框架的发展，提供更好的理解关键的陆架海洋生态系统驱动程序的分辨率差受到严重限制。我们将利用英国最近对海上自动驾驶车辆的投资和规划能力，调查北海一个已知在整个季节周期中经历可变物理，化学和生物条件的区域，包括确定在夏季经历低底层氧气水平的区域。海洋滑翔机将被用于进行重复断面超过150公里的距离，足以捕捉重要的陆架海功能，如锋和漩涡。AlterEco战略将使用小型车队来捕捉这些中尺度特征（通常规模约为100公里），但也将解决次中尺度变化（约为100米）。我们将受益于最近的成功和经验教训，开创性地部署水下滑翔机，并使用一套传感器，允许高分辨率同步测量关键生态系统指标。结合AlterEco团队的专业知识，我们不仅将为具有全球可转移性的海洋观测提供新的框架，而且还将提供诊断能力，以提高对陆架海生态系统健康和功能的理解。

Continental shelf seas are typically less than 200m deep and can be described by the shallow ocean surrounding continental land masses. Due to their accessibility, shelf seas are commercially and economically important, with oil and gas extraction alone in UK shelf seas valued at £37B pa. Despite occupying only 7% of the surface ocean, shelf seas also play a major role in the global carbon cycle and marine ecosystem. Shelf seas are 3-4 times more productive than open-ocean, are estimated to support more than 40% of carbon sequestration and support 90% of global fish catches providing a critical food source for growing coastal populations. However, shelf seas are also exposed to climate driven and anthropogenic stress that could have a profound impact on their biological productivity, oxygen dynamics and ecosystem function. Many processes contributing to this threat are related to regions that undergo vertical stratification. This process occurs when the bottom layer of shelf seas becomes detached from the atmospherically ventilated near surface layer. In temperate shelf seas stratification predominantly occurs as solar heating outcompetes the tide and wind-driven mixing to produce a warm surface layer, resulting in seasonal stratification over large areas of the NW European shelf seas. A combination of physical detachment from the surface and increased biological oxygen consumption in the bottom layer, accentuated by the enhanced productivity that stratification also supports in the upper ocean, can result in a drastically reduced bottom layer oxygen concentration. When oxygen levels get so low, they are classified as being oxygen deficient and this can be problematic for benthic and pelagic marine organisms and have a detrimental effect on ecosystem function. Evidence of increasing seasonal oxygen deficiency in the regions of North Sea by members of the AlterEco team and a recognised global increase in the extent of shelf sea and coastal oxygen deficiency calls for an urgent need to increase the spatial and temporal measurement of oxygen and a better understanding of the processes that lead to oxygen deficiency in shelf sea bottom waters. This need is severely impeded by the natural complexity of ecosystem functioning, the impact of a changing climate, connectivity between different regions of our shelf seas and large-scale external forcing from ocean and atmosphere. Current methods are severely restricted in resolving this complexity, due to the poor resolution in observational coverage, which calls for a new strategy for observing and monitoring marine ecosystem and environmental status.AlterEco seeks to address this challenge within the framework of the given call by the development of a novel monitoring framework to deliver improved understanding of key shelf sea ecosystem drivers. We will capitalise on recent UK investments in marine autonomous vehicles and planning capability to investigate an area of the North Sea known to undergo variable physical, chemical and biological conditions throughout an entire seasonal cycle, including areas identified to experience low bottom layer oxygen levels during summer months. Ocean gliders will be used to undertake repeat transects over a distance of ~150km, sufficient to capture important shelf sea features; such as fronts and eddies. The AlterEco strategy will employ small fleets of vehicles to capture these meso-scale features (typically ~100km in scale) but will also resolve sub-mesoscale variability (~100m). We will benefit from successes and lessons learnt from recent, pioneering deployments of underwater gliders and use a suite of sensors that permit high-resolution coincident measurements of key ecosystem indicators. Combining the expertise within the AlterEco team we will not only provide a new framework for marine observations that has global transferability, but also the diagnostic capability to improve understanding of shelf sea ecosystem health and function.