Particle aggregation at the edges of anticyclonic eddies and implications for distribution of biomass

[摘要] Acoustic measurements show that the biomass of zooplankton and mesopelagicfish is redistributed by mesoscale variability and that the signal extendsover several hundred meters depth. The mechanisms governing thisdistribution are not well understood, but influences from both physical(i.e. redistribution) and biological processes (i.e. nutrient transport,primary production, active swimming, etc.) are likely. This study examineshow hydrodynamic conditions and basic vertical swimming behavior act todistribute biomass in an anticyclonic eddy. Using an eddy-resolving 2.3 km-resolution physical ocean model as forcing for a particle-trackingmodule, particles representing passively floating organisms and organismswith vertical swimming behavior are released within an eddy and monitoredfor 20 to 30 days. The role of hydrodynamic conditions on the distributionof biomass is discussed in relation to the acoustic measurements. Particlesreleased close to the surface tend, in agreement with the observations, toaccumulate around the edge of the eddy, whereas particles released at depthgradually become distributed along the isopycnals. After a month they aredisplaced several hundreds meters in the vertical with the deepest particlesfound close to the eddy center and the shallowest close to the edge. Thereis no evidence of aggregation of particles along the eddy rim in the lastsimulation. The model results points towards a physical mechanism foraggregation at the surface, however biological processes cannot be ruled outusing the current modeling tool.

[学科分类] 海洋学与技术