Influence of the summer deep-sea circulations on passive drifts among the submarine canyons in the northwestern Mediterranean Sea

Abstract

Abstract. Marine biophysical models can be used to explore the displacement of individuals in and between submarine canyons. Mostly, the studies focus on the shallow hydrodynamics in or around a single canyon. In the northwestern Mediterranean Sea, knowledge of the deep-sea circulation and its spatial variability in three contiguous submarine canyons is limited. We used a Lagrangian framework with three-dimensional velocity fields from two versions of the Regional Ocean Modeling System (ROMS) to study the deep-bottom connectivity between submarine canyons and to compare their influence on the particle transport. From a biological point of view, the particles represented eggs and larvae spawned by the deep-sea commercial shrimp Aristeus antennatus along the continental slope in summer. The passive particles mainly followed a southwest drift along the continental slope and drifted less than 200 km considering a pelagic larval duration (PLD) of 31 d. Two of the submarine canyons were connected by more than 27 % of particles if they were released at sea bottom depths above 600 m. The vertical advection of particles depended on the depth where particles were released and the circulation influenced by the morphology of each submarine canyon. Therefore, the impact of contiguous submarine canyons on particle transport should be studied on a case-by-case basis and not be generalized. Because the flows were strongly influenced by the bottom topography, the hydrodynamic model with finer bathymetric resolution data, a less smoothed bottom topography, and finer sigma-layer resolution near the bottom should give more accurate simulations of near-bottom passive drift. Those results propose that the physical model parameterization and discretization have to be considered for improving connectivity studies of deep-sea species.

Male Deep-Sea Shrimps Aristeus antennatus at Fishing Grounds: Growth and First Evaluation of Recruitment by Multilocus Genotyping

“…This is a well-defined western Mediterranean current that extends to 300-400 m depth, with a general southwest flow that follows the continental slope from Italy to Spain [52,53]. Using hydrodynamic models to predict connectivity among A. antennatus populations by passive egg and larval drift among submarine canyons in our study region, Clavel-Henry et al predicted a global pattern of southward dispersal, according to the Northern Current [22]; however, the authors also predicted high average retention rates in submarine canyons in some models (reaching up to 60%). Our genetic analyses support these predictions, showing assignation rates of 50-70% for all juveniles and pre-adult males captured in 2016 at the Palamós fishing ground to the simulated F1 between females and their spermatophores sampled in 2015 (Table 3), as well as the contribution of migrants from northern grounds ( Table 4).…”

“…After hatching on the bottom substrate, the first larval stages perform an ontogenic migration through the water column to the surface to optimize feeding and enhance development of the late larval stages [21]. Surface currents disperse these protozoea and zoea larval stages [22]. Finally, the decapodid stage organisms exhibit a downward vertical migration to deep waters, where they settle [7,23].…”

Indicators to assess interannual variability in marine connectivity processes: a semi-theoretical approach

“…The velocity fields from the hydrodynamic model are provided daily for the climatological year and between the years 2006 and 2020 on a grid with a spatial resolution around 2 km and vertically discretized over 40 sigma layers. Details on the implementation and validation of the climatological years are provided in [26, 27]. The 2006-2020 model has been forced with interannual atmospheric data provided by the Copernicus’ Climate reanalysis database (ERA-Interim from 2006 to 2016 and ERA-5 from 2016 to 2020 [28, 29]) and provided by the Cross-Calibrated Multi-Platform (version 3) from the Remote Sensing System [30].…”

Systematic Conservation Planning at an Ocean Basin Scale: Identifying a Viable Network of Deep-Sea Protected Areas in the North Atlantic and the Mediterranean

“…Whereas this study did not evaluate the performance of the current MPA network in maintaining deep-sea benthic connectivity, similar particle-tracking model assessments have been undertaken quite recently at sub-basin scale in the North Atlantic (Fox et al, 2016;Ross et al, 2017;Kenchington et al, 2019b) and at smaller scale in the Mediterranean (Basterretxea et al, 2012;Clavel-Henry et al, 2019). While the NAFO VME fishing closures in the northwest Atlantic (Kenchington et al, 2019b) and MPAs in the EEZs such as the west of the United Kingdom and Ireland (Fox et al, 2016;Ross et al, 2017) and the Mediterranean (IUCN, 2019) form networks, these are the result of ad hoc additions of new fisheries closures and MPAs over time without any attempt to take network properties such as connectivity into account.…”

“…This would result in improved within-network exchange increasing genetic variability and hence overall resilience (Ross et al, 2017;Kenchington et al, 2019b;Manea et al, 2020). However, building networks that are highly connected is extremely challenging in the deep sea since lifehistory traits and the behaviour of deep-sea larvae remains largely unknown (Hilário et al, 2015;Clavel-Henry et al, 2019;Kenchington et al, 2019b), thus limiting the precision of predicted connectivity patterns. Approximate estimates may be modelled, as they were here, where different release depths were used to account for larval dispersion behaviour strategies rather than model specific swimming, floating and sinking parameters.…”