Bivalve shell-based, high-resolution multi-proxy reconstruction of marine primary production – Pecten maximus, Bay of Brest

初级生产者构成海洋食物网的基础，控制较高营养水平的种群规模和鱼类种群补充。海洋光自养生物也占全球净初级生产量的近一半，即它们为海洋(和大气)补充氧气并固定大量碳。尽管它与海洋生态系统和全球气候的功能密切相关，但过去的初级生产动态和控制它们的机制并没有得到很好的描述。近岸沿海环境和人类对生物地球化学循环造成重大干扰之前的情况尤其如此。关于海洋初级生产力变化的现有数据来源：(1)没有提供必要的时间分辨率来解决短期和空间受限的浮游植物水华，特别是在浅水；(2)数据太短，无法区分初级生产的趋势和低频率循环；(3)没有涵盖自养光生物的全部，其中不仅包括浮游植物和蓝藻，即微型底栖植物和大型藻类。因此，该项目将开发一种创新技术，能够以双壳类软体动物的贝壳为基础，提供可靠的、受时间限制的、从季节性到年际的关于沿海近岸环境过去初级生产动态的数据。为此，我们将测试和提炼用于初级生产的现有代理(代理)，并开发新的代理并将其集成到多重代理方法中。为了从机理上了解关于海洋光自养生物的种类组成和数量的信息是如何记录在贝壳的化学性质(巴/钙、钼/钙、锂/钙、碳和氮的稳定同位素、氧的三同位素组成、色素)和颜色(色调和饱和指数)中的，将进行野外和水箱实验，在此期间可以密切监测和操纵环境变量。由于这项研究涉及活体双壳类动物的实验，我们选择了快速生长的物种Pecten max和一个已经被非常详细地研究的生态系统，法国布列斯特湾。随后将通过应用从考古遗址收集的亚化石贝壳来确定人类对布列斯特湾初级生产动态的影响，包括(I)光自养生物的季节性发生以及浮游植物水华的强度、频率和季节时间，(Ii)物种组成和生物量随时间的变化，以及(Iii)居住在海底的生物和生活在海面附近的生物之间的联系的变化。这项研究的结果将极大地推动海洋科学的发展，包括古生态学、古气候学和渔业科学。

Primary producers form the basis of marine food webs, control population sizes at higher trophic levels and fish stock recruitment. Marine photoautotrophic organisms are also responsible for nearly half of the global net primary production, i.e., they replenish the ocean (and atmosphere) with oxygen and fix substantial amounts of carbon. Despite its outstanding relevance for the functioning of marine ecosystems and global climate, past primary production dynamics and mechanisms controlling them are not well characterized. This is particularly true for nearshore coastal environments and for times prior to significant human perturbation of biogeochemical cycles. Available data sources for changes in marine primary production (i) do not provide the necessary temporal resolution to resolve short-lived and spatially restricted phytoplankton blooms, specifically in shallow waters, (ii) are too short to distinguish trends from low-frequency cycles of primary production and (iii) do not cover the entirety of photoautotroph taxa which include more than just phytoplankton and cyanobacteria, i.e. microphytobenthos and macroalgae. Therefore, this project will develop an innovative technique that can provide reliable, temporally well-constrained, seasonally to inter-annually resolved data on past primary production dynamics in coastal nearshore environments based on shells of bivalve mollusks. For this purpose, we will test and refine existing proxies (surrogates) for primary production, and develop new proxies and integrate them in a multiproxy approach. In order to obtain a mechanistic understanding of how information on the species composition and number of marine photoautotrophs is recorded in chemical properties (Ba/Ca, Mo/Ca, Li/Ca, stable isotopes of carbon and nitrogen, triple isotope composition of oxygen, pigments) and color (hue and saturation index) of the shells, field and tank experiments will be conducted during which environmental variables can be closely monitored and manipulated. Since the study involves experiments with living bivalves we chose the fast-growing species, Pecten maximus, and an ecosystem that has been studied in great detail, the Bay of Brest, France.The multiproxy approach will subsequently by applied to subfossil shells collected from an archaeological site to determine the human impact on primary production dynamics of the Bay of Brest including (i) the seasonal occurrence of photoautotrophs as well as the intensity, frequency and seasonal timing of phytoplankton blooms, (ii) shifts in species composition and biomass through time and (iii) changes in the link between organisms inhabiting the sea floor and those living near sea surface. Results of this study will significantly advance marine sciences including paleoecology, paleoclimatology and fisheries sciences.