Hydrodynamic provinces and oceanic connectivity from a transport network help designing marine reserves

Abstract

Oceanic dispersal and connectivity have been identified as crucial factors for structuring marine populations and designing marine protected areas (MPAs). Focusing on larval dispersal by ocean currents, we propose an approach coupling Lagrangian transport and new tools from Network Theory to characterize marine connectivity in the Mediterranean basin. Larvae of different pelagic durations and seasons are modeled as passive tracers advected in a simulated oceanic surface flow from which a network of connected areas is constructed. Hydrodynamical provinces extracted from this network are delimited by frontiers which match multiscale oceanographic features. By examining the repeated occurrence of such boundaries, we identify the spatial scales and geographic structures that would control larval dispersal across the entire seascape. Based on these hydrodynamical units, we study novel connectivity metrics for existing reserves. Our results are discussed in the context of ocean biogeography and MPAs design, having ecological and managerial implications.

Edge anisotropy and the geometric perspective on flow networks

“…The thus obtained correlation-based flow networks 25 (as well as similar approaches based on Lagrangian dynamics 26,27 ) have numerous potential applications in the field of atmospheric or oceanic flows. Note that the term flow network is sometimes also used as a synonym for transportation networks in technological applications such as power grids.…”

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“…Particularly the southern part of north-western shelf (area 9) is connected to the region on the southwestern shelf off the Bosphorus (area 1) as well as the southern shelf off Samsun (area 3) is connected to the northeast Black Sea off the Azov Sea (areas 6 and 5) via ocean currents when assuming a 36-day pelagic larval duration. Design of MPA's should therefore focus on these regions, although it should be noted, that this study is based on anchovy larvae and that species with different pelagic larval durations will show different connectivity patterns (Rossi et al, 2014).…”

Lagrangian Transport of Marine Litter in the Mediterranean Sea

“…Different definitions of such a process are available in the literature, typically related with tracer particle Lagrangian displacement described as a stochastic process, and spanning through quite different dispersion scenarios: e.g., particle trapping in porous media (e.g., Koch and Brady, 1985), in convective cells (e.g., Guyon et al, 1987), in anomalous diffusion situations (Young, 1988). In oceanographic flows, particle retention has been assessed with tools derived from dynamical systems theory (e.g., Castiglione et al, 1999;Cencini et al, 1999); the attractive properties of Lagrangian coherent structures may play an important trapping role (Peacock and Haller, 2013; for a Mediterranean application see Rossi et al, 2014). Froyland et al (2014) quantitatively assessed the location and effectiveness of particle attraction areas in the world ocean on the basis of synthetic Lagrangian trajectories interpreted in a Markovian approximation.…”