Quantifying the effects of fragmentation of connectivity networks of deep-sea vulnerable marine ecosystems

Aim

Protection of vulnerable marine ecosystems (VMEs) in the high seas has focussed on identifying concentrations of indicator species and prohibiting the operation of bottom-contact fishing gears where those occur in significant concentrations. Most such species have planktonic larvae and depend on dispersal networks for inter-generational persistence. Yet, connectivity amongst patches of VME has seldom been considered when spatial management measures are introduced. Here, the relative importance of individual patches for the maintenance of their connectivity networks is evaluated, and a prioritization scheme for management action is proposed. Effective conservation measures should maintain approximately natural network configurations whenever possible.

Location

Grand Bank and Flemish Cap, Northwest Atlantic Ocean.

Methods

3-D Lagrangian particle tracking was used to model larval dispersal connections between known patches of each of seven groups of benthic invertebrate taxa, previously recognized as indicators of VME. Connectivity networks were constructed and the effects of habitat loss simulated by systematic removal of whole patches, to determine the importance of each patch to connectivity within its respective network.

Results

The various patches differed widely in their contributions to network connectivity. Each taxon group had both some patches that, if removed from the network, would result in a major decline in connectedness but also several which could be lost with negligible consequences for the remainder.

Main Conclusions

While protecting each patch of VME has conservation value, the wide variation in connectedness shows that some patches are much more critical than others to the long-term persistence of the taxa, providing a foundation for prioritization of conservation actions.