Cermeño Pedro, Falkowski Paul G, Romero Oscar E, Schaller Morgan F, Vallina Sergio M
Departamento de Biología Marina y Oceanografía, Instituto de Ciencias del Mar, 08003 Barcelona, Spain;
Environmental Biophysics and Molecular Ecology Program, Department of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901; Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854;
Proc Natl Acad Sci U S A. 2015 Apr 7;112(14):4239-44. doi: 10.1073/pnas.1412883112. Epub 2015 Mar 23.
Marine diatoms are silica-precipitating microalgae that account for over half of organic carbon burial in marine sediments and thus they play a key role in the global carbon cycle. Their evolutionary expansion during the Cenozoic era (66 Ma to present) has been associated with a superior competitive ability for silicic acid relative to other siliceous plankton such as radiolarians, which evolved by reducing the weight of their silica test. Here we use a mathematical model in which diatoms and radiolarians compete for silicic acid to show that the observed reduction in the weight of radiolarian tests is insufficient to explain the rise of diatoms. Using the lithium isotope record of seawater as a proxy of silicate rock weathering and erosion, we calculate changes in the input flux of silicic acid to the oceans. Our results indicate that the long-term massive erosion of continental silicates was critical to the subsequent success of diatoms in marine ecosystems over the last 40 My and suggest an increase in the strength and efficiency of the oceanic biological pump over this period.
海洋硅藻是沉淀二氧化硅的微藻，它们在海洋沉积物中的有机碳埋藏量占比超过一半，因此在全球碳循环中发挥着关键作用。在新生代（6600万年前至今）期间，它们的进化扩张与相对于其他硅质浮游生物（如有孔虫）对硅酸具有更强的竞争能力有关，有孔虫通过减轻其硅质外壳的重量而进化。在这里，我们使用一个数学模型，其中硅藻和有孔虫竞争硅酸，以表明观察到的有孔虫外壳重量的减轻不足以解释硅藻的兴起。利用海水的锂同位素记录作为硅酸盐岩石风化和侵蚀的指标，我们计算了硅酸进入海洋的输入通量的变化。我们的结果表明，在过去4000万年中，大陆硅酸盐的长期大规模侵蚀对于硅藻随后在海洋生态系统中的成功至关重要，并表明在此期间海洋生物泵的强度和效率有所提高。
