Quantifying marine larval dispersal to assess MPA network connectivity and inform future national and transboundary planning efforts

A Marine Protected Area (MPA) network, in which multiple reserves are designated in a region, can promote the protection of biodiversity across space. To be effective as a network, the design must consider whether MPAs are likely to be connected through the movement of individuals of species of interest. Additionally, network design may explicitly incorporate design features that promote biodiversity in unprotected habitats through the dispersal or spillover of multiple species. Patterns of dispersal and the ability of MPAs to function as an interacting network, however, are difficult to estimate at broad and transboundary spatial scales, and therefore connectivity is often not fully integrated in the design and assessment of MPA networks. Here, we model the dispersal of multiple nearshore species to estimate the potential connectivity of the existing MPAs in British Columbia, Canada, including connections to MPAs in the United States by simulating dispersal using a biophysical model with regional oceanographic currents. We found that MPAs in BC potentially meet connectivity design criteria for nearshore invertebrate species: the majority of MPAs (65-90%) are likely to exchange individuals (i.e. functional connectivity) and support persistent metapopulations, and more than half the unprotected coast (55-85%) receives a large proportion of the larvae produced in MPAs. Furthermore, we found that species dispersal abilities and the level of exposure of an MPA to open ocean can predict dispersal distance when we account for the random effects of dispersal location and season. Therefore, future predictions of connectivity are possible based on these core biological and physical attributes, without running new simulations. Together, these analyses provide a robust and novel assessment of multi-species connectivity that can support the design of new MPAs with transboundary connectivity on the northwest coast of North America.