Hydrodyamic connectivity in the Seaflower Reserve system and its potential impact on biological connectivity

Abstract

The influence of the ocean currents over marine population connectivity is pivotal in territory planning since they should be considered in marine protected areas (MPA’s) design and its implementation, maritime spatial planning strategies, restoration plans, among others. Their influence is also vital to broadening the relationship knowledge between oceanographic drivers and ecosystems configuration. However, and despite their importance, knowledge of ocean currents and its role in corals connectivity is poorly known at the Seaflower Marine Reserve, an area that harbors the third large true barrier reef in the world and that was declared as Biosphere Reserve in 2000. In consequence, the aim of this work is characterize larval transport patterns associated with the surface currents that lead connectivity at the Reserve. To achieve this aim, we had simulated the advection of buoyant coral larvae of Acropora Palmata during nine spawning events. Larval dispersal patterns were obtained through the offline coupling of a high spatiotemporal resolution hydrodynamic field and a biophysical lagrangian model for particle dispersion. The ocean currents fields were generated through a Regional Ocean Modelling System (ROMS) adequately configured for the domain. Larvae dispersion was carried out throughout an Individual-Based Model (Ichthyop). Results show that there are heterogeneous connectivity patterns during the spawning events at seasonal and inter-annual scales. This behavior seems to be associated with the high spatiotemporal dynamic variability in the region, such as the Caribbean Current bifurcation close to the Nicaraguan Rise, the intrusion-formation of mesoscale or sub-mesoscale eddies, and the semi-permanent presence of the Panamá-Colombia Gyre (PCG). We also identified Serranilla, B.Alicia, and B.Nuevo as the most important sources for potential connectivity (in terms of events recurrence), even when some mortality rates are included (effective connectivity). In contrast, the weakest sources were the southernmost reefs (Albuquerque, San Andrés, and Bolívar) due to the continuous influence of the PCG. In the case of the potential and effective connectivity of the sinks, the most recurrent reefs were Serranilla, Providencia, Quitasueño, and Serrana while the least were B.Nuevo and Roncador. Recruitment distances oscillate between 0 km (for self-recruitment) and 500 km. However, larvae settlement is likelier until 50 km from the release point. In the case of recruitment time, larvae settle until the end of the pelagic larval duration (PLD), but higher rates of settlement were identified between 3 and 4 days after the spawn.

Our results highlight the need for the incorporation of the most important source areas in the current MPA zonification, that could lead to the improvement of the MPA effectiveness. Findings also suggest the possibility to implement an MPA network between Jamaica and Colombia that could allow the populations to be resilient to environmental changes and less prone to local extinctions. We also stand out the need for the suitable representation of the dynamic oceanic processes in whole water column since they play a crucial role in larval dispersal. Among the most important dynamical features are: meso and sub-mesoscale eddies, fronts, and filaments.nts.