Department of Biology, University of Bergen, Thormøhlensgate 53 A/B, 5020 Bergen, Norway
National Institute of Aquatic Resources - DTU Aqua, Technical University of Denmark, Kemitorvet, Building 202, 2800 Kgs Lyngby, Denmark.
J R Soc Interface. 2017 Nov;14(136). doi: 10.1098/rsif.2017.0453.
Turbulence and coherent circulation structures, such as submesoscale and mesoscale eddies, convective plumes and Langmuir cells, play a critical role in shaping phytoplankton spatial distribution and population dynamics. We use a framework of advection-reaction-diffusion equations to investigate the effects of turbulent transport on the phytoplankton population growth and its spatial structure in a vertical two-dimensional vortex flow field. In particular, we focus on how turbulent flow velocities and sinking influence phytoplankton growth and biomass aggregation. Our results indicate that conditions in mixing and growth of phytoplankton can drive different vertical spatial structures in the mixed layer, with the depth of the mixed layer being a critical factor to allow coexistence of populations with different sinking speed. With increasing mixed layer depth, positive growth for sinking phytoplankton can be maintained with increasing turbulent flow velocities, allowing the apparently counter-intuitive persistence of fast sinking phytoplankton populations in highly turbulent and deep mixed layers. These dynamics demonstrate the role of considering advective transport within a turbulent vortex and can help to explain observed phytoplankton biomass during winter in the North Atlantic, where the overturn of deep convection has been suggested to play a critical role in phytoplankton survival.
紊流和相干环流结构，如亚中尺度和中尺度涡旋、对流羽流和Langmuir 细胞，在塑造浮游植物的空间分布和种群动态方面起着至关重要的作用。我们使用平流-反应-扩散方程框架来研究紊流输运对浮游植物种群增长及其在垂直二维涡旋流场中的空间结构的影响。特别是，我们关注的是紊流速度和沉降如何影响浮游植物的生长和生物量聚集。研究结果表明，混合和浮游植物生长的条件可以驱动混合层中不同的垂直空间结构，混合层的深度是允许具有不同沉降速度的种群共存的关键因素。随着混合层深度的增加，对于沉降的浮游植物，在增加的紊流速度下可以维持正的生长，这使得在高度紊流和深混合层中快速沉降的浮游植物种群的持续存在变得明显违背直觉。这些动力学现象证明了在紊流涡旋中考虑平流输运的作用，并有助于解释北大西洋冬季观测到的浮游植物生物量，在那里，深层对流的翻转被认为对浮游植物的生存起着关键作用。
