Coupled benthic-pelagic processes in the Patagonian shelf break

BÁRBARA C. FRANCO; ELBIO D. PALMA; VINCENT COMBES

Praga, República Checa

Conferencia; 26th General Assembly of the International Union of Geodesy and Geophysics (IUGG); 2015

The largest aggregations of the Patagonian scallop (Zygochlamys patagonica), a filter feeder of phytoplankton, are located along the argentinean outer shelf and continental slope following the surface signature of the Patagonian Shelf Break Front (PSBF). The region currently supports one of the most important scallop fisheries in the world. The PSBF is associated with areas of high concentration of phytoplankton and therefore it has been suggested that coupled benthic-pelagic processes would be the main process explaining the location of the major scallop beds. In this work we investigate this hypothesis using stochastic particle tracking simulations driven with flow and diffusivity fields generated by idealized and realistic high-resolution hydrodynamic numerical models. To analyze the dynamics of coupled benthic-pelagic processes particles were released at the surface over shelf break in an idealized model. The model results showed that semidiurnal (tidally driven) oscillations induce high mixing processes over the shelf break, with horizontal displacements of ~10 km of the particles. These horizontal movements interact with the local stratification generating disturbances in the density field that enhanced vertical particle displacements and allowed benthic-pelagic coupling. Such coupling and vertical transports of particles reaching the bottom (~200 m depth) occur only in the model which is forced with tides and a slope current. Particles released at the surface of the PSBF in the realistic models reach the bottom near the location of the main scallop beds, further supporting the proposed coupling mechanism. It is also interesting to note that an important amount of particles were also dispersed offshore along the continental slope.