The Significance of Macroalgal Detritus for Marine Food Webs and Blue-Carbon Sequestration

海洋植物吸收二氧化碳，在大气二氧化碳水平上升的世界中，沿海植被生态系统中的碳汇可以在地质时间尺度上封存二氧化碳，现在被称为“蓝碳”。海洋大型藻类（MA）是高生产力的大型植物，目前覆盖约350万平方公里的亚沿海海底，并提供1521 Tg C年-1的净初级生产全球。然而，千年生态系统在很大程度上被排除在蓝碳固存的估计之外，因为它们主要生长在坚硬的基质上，这阻止了富含碎屑的沉积物的积累。但是，虽然海洋生物碳（CMA）不能在源生态系统内积累，但据估计，高达82%的CMA从源生态系统输出到更深的海底栖息地，为沿海区以外的海洋海底生态系统提供了大量的碳补贴，并/或有助于海底的长期碳埋藏。海洋峡湾最近被认为是具有全球意义的主要碳汇，尽管它们的低面积覆盖率占全球年度碳封存的11%。每单位面积，峡湾有机碳埋藏率是全球海洋平均水平的100倍，峡湾沉积物中的有机碳含量是海洋上涌区生物沉积物的两倍。在北极峡湾的研究表明，CMA贡献了高达60%的C固存，这将使大型藻类成为蓝色碳固存的主要贡献者，以及一般的全球地球化学循环。CMA的矿化和固存都受到很好的限制，然而，MA碎屑的实际重要性，因此来自大型藻类的碳，作为对深海异地（汇）底栖生物群和沉积物的一项主要生态系统服务，地理位置好-该项目将量化MA碳对C固存的贡献，并作为苏格兰底栖动物的食物补贴。通过相机勘测、沉积物取样和分析、稳定同位素分析和同位素示踪实验，对峡湾进行了综合研究。根据斯米顿等人（2017）的方法，该项目将对海洋洛赫沉积物中的MA碳补贴进行预测（一阶）评估。气候变化是一个全球性问题，提高对蓝碳生态系统的理解和管理对于减缓气候变化行动非常重要，并与联合国可持续发展目标3，13和14直接相关。与苏格兰蓝碳论坛的密切合作将有助于快速转化为国家气候减缓和适应政策。除了SUPER特定的培训活动外，候选人将接受广泛的实地和实验室技术培训，包括设计和进行新型同位素示踪实验，食物网建模和地理信息系统。预计学生还将在AWI Bremerhaven的外部合作者Inka Bartsch博士的实验室中度过一段时间。

Marine plants draw down CO2, and in a world of rising atmospheric CO2 levels carbon sinks in vegetated coastal ecosystems can sequester CO2 on geological time scales and are now referred to as 'Blue Carbon'. Marine macroalgae (MA) are highly productive macrophytes that currently cover approximately 3.5 million km2 of sublittoral seabed and provide 1521 Tg C yr-1 of net primary production globally. Nevertheless, MA have largely been excluded from estimates of blue carbon sequestration because they predominantly grow on hard substrates, which prevent the accumulation of detritus-rich sediments. But while MA carbon (CMA) cannot accumulate within the source ecosystem, it has been estimated that up to 82% of CMA is exported from the source ecosystem to seabed habitats at greater depths, providing a significant carbon subsidy to marine seabed ecosystems beyond the coastal zone and/or contributing to long-term carbon burial in the ocean seabed.Shelf seas are known for their significant stocks of carbon, and marine fjords have recently been proposed as major C sinks of global significance, despite their low area coverage accounting for 11 % of global annual carbon sequestration. Per unit area, fjord organic carbon burial rates are one hundred times as large as the global ocean average, and fjord sediments contain twice as much organic carbon as biogeneous sediments underlying the upwelling regions of the ocean. Studies in Arctic fjords suggest that CMA contributes up to 60% to C sequestration which would render macroalgae a major contributor to blue carbon sequestration, and global biogeochemical cycles in general.Both remineralisation and sequestration of CMA are poorly constrained, however, and the actual importance of MA detritus, and hence carbon derived from macroalgae, as a major ecosystem service to deep allochthonous (sink) benthic biota and sediments still needs to be addressed in a quantitative, geographically well-constrained investigation.This project will quantify the contribution of MA carbon to C sequestration and as food subsidy to benthic fauna in Scottish fjords through a combination of camera surveys, sediment coring and analysis, stable isotope analysis and isotope tracing experiments. Following the methodology of Smeaton et al. (2017), the project will deliver a predictive (first-order) assessment of the MA carbon subsidy into sea loch sediments.Climate change is a global issue, and improved understanding and management of Blue Carbon ecosystems is important for climate mitigation action, and directly relevant to UN Sustainable Development Goals 3, 13 and 14. Close collaboration with the Scottish Blue Carbon Forum will facilitate quick translation into national climate mitigation and adaptation policy.In addition to SUPER specific training events, the candidate will be trained in a wide range of field and laboratory techniques, including the design and conduction of novel isotope tracing experiments, food web modelling and GIS. It is envisaged that the student will also spend some time in the laboratory of our external collaborator Dr. Inka Bartsch at AWI Bremerhaven.