"Effect of small scale transport processes on phytoplankton distribution in coastal seas" by I. Hernández-Carrasco et al. published in Scientific Reports

Scientific Reports publishes the results of a multidisciplinary study undertaken by researchers from SOCIB, IMEDEA (UIB-CSIC), the Mediterranean Institute of Oceanography (MIO, France) and the Laboratoire d’Etudes en Géophysique et Océanographie Spatiales (LEGOS, France). It examines the role of small scale transport processes based on high resolution observations of surface currents and their relationships with remotely-sensed phytoplankton concentrations in a coastal region.

Phytoplankton is a key element of oceanic ecosystems: planktonic primary producers utilize dissolved inorganic carbon, sunlight and nutrients to create organic matter at the surface, which can then be stored in the deep ocean. Through this process, they sustain marine food webs and withdraw carbon dioxide from the atmosphere, hence indirectly controlling the Earth climate. Physical factors induced by the turbulent oceanic flow are now recognized to play a crucial role in regulating phytoplankton dynamics. While the impacts of large-scale ocean dynamics on biological activity are relatively well documented, the role of small-scale transport processes is still poorly understood, noticeably due to the lack of continuous high-resolution observations.

The scientists analyzed High Frequency Radar velocities using a novel metric called Lagrangian divergence, together with other well-established techniques, which are all derived from the Complex Systems to unravel the small scale geometrical structures of the oceanic flow (fronts, filaments, eddies, etc). When compared against chlorophyll-a concentrations measured by satellite, the combination of these powerful diagnostics permits to distinguish strongly convergence structures along which particles and phytoplankton standing stocks cluster, and areas of accrued divergence where upward vertical velocities prevail, promoting new production of phytoplankton through enhanced nutrient supply. 
This study provides an improved understanding and assessment of the bio-physical interactions occurring in the ocean at various spatial and temporal scales.

These results open up new perspectives to better appraise the effects of transport processes on, and possibly to make short-term projections of material carried away by ocean currents. Possible future applications include the study of plastic debris accumulation zones, jellyfish aggregations, the fate of harmful algal blooms and oil spill management. 


Hernández-Carrasco, I., Orfila, A., Rossi, V. and Garçon, V. (2018). Effect of small scale transport processes on phytoplankton distribution in coastal seas, Scientific Reports, 8:8613 doi: 10.1038/s41598-018-26857-9