Connectivity of benthic priority marine species within the Scottish MPA network | Scottish Marine and Freshwatwe Science Vol 4 No 2

Our modelling approach involved the following components. 1. The output from an existing hydrodynamic model covering Scottish waters and the compilation of a climatological flow-field to represent "average" conditions. 2. Proposed MPA locations as "source" and "target" areas for the dispersal of individual species (at the relevant life stage for dispersal). 3. Species life cycles divided into categories, based on common biological characteristics that may influence dispersal patterns, such as the duration of larval phase/settlement window and season of spawning. 4. Simplistic Individual-Based Models that allow the characterisation at individual level of the origin, destination and trajectory of particles representing PMF larvae, and could also be used to simulate the interplay between physical transport and biological characteristics such as development, mortality and "behaviour", although such interactions were not taken into account here largely due to lack of reliable relevant biological information. 5. Simulation results processed to quantify connectivity and export/import out of/into proposed MPA locations to assess the most suitably located sites and the replication needed. With respect to 3, year was split into quarters to consider approximate spawning windows, whilst PLD was split into 11 daily time intervals for the 18 PMF species considered. The lack of information on even the most basic behavioural attributes in most cases, such as vertical distribution in the water column, meant that species behaviour could not be considered. An existing hydrodynamic model covering Scottish waters and the compilation of a climatological flow-field to represent "average" conditions was used to predict larval transport. Proposed MPA locations were considered as "source" and "target" areas for the dispersal of individual species (at the relevant life stage for dispersal).

A biophysical modelling approach that accounts for regional oceanographic variation and some degree of biological realism was used to estimate larval transport of 18 benthic invertebrates identified as priority marine features for possible nature conservation MPAs. Mean transport distance was mostly related to the duration of the pelagic larval phase (PLD), although season of spawning and distance to shore were also important factors. Larvae of species with a PLD = 30 days that were not solely associated with sea lochs or near-shore regions could be advected from the Celtic Sea to the Greater North Sea OSPAR sub-region. These species include tall sea pen, burrowing anemone, spiny lobster and most bivalve molluscs. Due to the limited distance between possible MPAs, connectivity among protected regions should be possible for many species with PLD = 10 d within OSPAR subregions. Those species at risk of local impacts due to low connectivity were species with a short PLD (burrowing amphipod, northern feather star, pink soft coral and northern sea fan) and/or present only in a small number of MPAs (heart cockle and horse mussel). Possible MPAs that were too close to shore to resolve in this analysis are also likely to be less dispersive environments than open water possible MPA sites. The model estimates of larval transport could be significantly influenced by larval behaviour and hatching times, highlighting the need for better information on these parameters. Information on habitat suitability is also needed to resolve suitable settlement areas. Future high resolution hydrodynamic models should allow us to improve our estimation of connectivity.