Designing marine reserve networks to mitigate larval dispersal volatility with the connectivity portfolio effect

Context Marine reserve networks designed to enhance larval dispersal provide important biodiversity benefits. Designs are commonly based on time-averaged means of dispersal estimates. It is unclear whether they capture the connectivity portfolio effect, by which temporal variation in individual reserve performance is buffered by the entire network.

Objectives To evaluate the implications of dispersal variability and derive general rules for network design.

Methods We modelled larval dispersal of four commercially important reef species for 20 years in Southeast Sulawesi, Indonesia. We built reserve network scenarios informed by temporal dispersal as either an interannual mean or dispersal for individual years. We then evaluated reserve network performance.

Results Plectropomus leopardus and Siganus canaliculatus experienced higher variability in interannual larval flow compared to Lutjanus malabaricus and Octopus vulgaris. We discover that using a single time-averaged mean dispersal estimate can create subpar reserve networks in highly variable systems. Mean dispersal was suitable for less variable species such as O. vulgaris, but not for more variable species where high larval flow was not protected over time. By explicitly identifying reefs contributing a high amount of larval flow in each of the 20 years, we were able to improve network designs and provide a more consistent protection of larval supply over time.

Conclusions We develop methods to improve network performance by protecting reefs with high larval flow contribution across years. The steps outlined here illustrate how information from multitemporal connectivity datasets can help inform a spatial prioritisation framework to accommodate larval dispersal volatility.