Pteropoda abundances in multinet samples

The vertical flux and sedimentation rate of planktic foraminiferal tests are quantified and a global planktic foraminiferal CaCO3 budget is presented. Test and calcite flux rates are calculated according to the distribution of species obtained from multinet and sediment trap samples. Modern planktic foraminiferal population dynamics are discussed as a prerequisite for the quantification of the calcite budget, highlighting the importance of ecological, autecological (e.g., reproduction), and biogeochemical conditions that determine the presence or absence of species. To complete the open-marine, particulate CaCO3 inventory, the contribution of coccolithophores, pteropods, and calcareous dinophytes is discussed. Based on the studied regions, the global planktic foraminiferal calcite flux rate at 100 m depth amounts to 1.3–3.2 Gt/yr, equivalent to 23–56% of the total open marine CaCO3 flux. The preservation of tests varies on a regional and temporal scale, and is affected by local hydrography and dissolution. During most of the year (off-peak periods), many tests dissolve above 700-m water depth while settling through the water column, with on average only 1–3% of the initially exported CaCO3 reaching the deep-seafloor. Pulsed flux events, mass dumps of fast settling particles, yield a major contribution of tests to the formation of deep-sea sediments. On average, ~25% of the initially produced planktic foraminiferal test CaCO3 settles on the seafloor. The total planktic foraminiferal contribution of CaCO3 to global surface sediments amounts to 0.36–0.88 Gt/yr, ?32–80% of the total deep-marine calcite budget.

本研究量化了浮游有孔虫壳体（planktic foraminiferal tests）的垂直通量与沉积速率，并构建了全球浮游有孔虫碳酸钙（CaCO₃）收支体系。壳体与方解石通量速率依据分层采样网（multinet）及沉积物捕集器（sediment trap）采集的物种分布数据计算得到。现代浮游有孔虫种群动态被作为方解石收支量化的前置条件予以讨论，重点阐明了调控物种存续与否的生态、个体生态（autecological，如繁殖过程）及生物地球化学条件的关键作用。为完善开阔海洋颗粒态碳酸钙编目，本文还探讨了颗石藻（coccolithophores）、翼足类（pteropods）与钙质甲藻（calcareous dinophytes）的贡献。基于研究区域的观测数据，100米水深处的全球浮游有孔虫方解石通量速率为1.3–3.2 Gt/yr，约占开阔海洋总碳酸钙通量的23%–56%。壳体的保存状况存在区域与时间尺度上的差异，受局地水文条件与溶解作用共同影响。在一年的多数时段（非峰值期），多数壳体在沉降穿过水柱的过程中于700米以浅的水层发生溶解，平均仅1%–3%的初始输出碳酸钙能够抵达深海海底。脉冲通量事件，即快速沉降颗粒的大规模堆积事件，可使壳体对深海沉积物的形成贡献占据主导地位。平均而言，初始生成的浮游有孔虫壳体碳酸钙中约25%会沉降至海底。浮游有孔虫向全球表层沉积物贡献的碳酸钙总量为0.36–0.88 Gt/yr，约占深海方解石总收支的32%–80%。