Sensitivity of marine protected area network connectivity to atmospheric variability

International efforts are underway to establish well-connected
systems of marine protected areas (MPAs) covering at least
10% of the ocean by 2020. But the nature and dynamics
of ocean ecosystem connectivity are poorly understood,
with unresolved effects of climate variability. We used
40-year runs of a particle tracking model to examine
the sensitivity of an MPA network for habitat-forming
cold-water corals in the northeast Atlantic to changes in
larval dispersal driven by atmospheric cycles and larval
behaviour. Trajectories of Lophelia pertusa larvae were strongly
correlated to the North Atlantic Oscillation (NAO), the
dominant pattern of interannual atmospheric circulation
variability over the northeast Atlantic. Variability in trajectories
significantly altered network connectivity and source–sink
dynamics, with positive phase NAO conditions producing
a well-connected but asymmetrical network connected from
west to east. Negative phase NAO produced reduced
connectivity, but notably some larvae tracked westwardflowing
currents towards coral populations on the mid-Atlantic
ridge. Graph theoretical metrics demonstrate critical roles
played by seamounts and offshore banks in larval supply and
maintaining connectivity across the network. Larval longevity
and behaviour mediated dispersal and connectivity, with
shorter lived and passive larvae associated with reduced
connectivity. We conclude that the existing MPA network is
vulnerable to atmospheric-driven changes in ocean circulation.