From single species to multi-species connectivity networks for MPA positioning – the Gulf of Lions case study

The creation of networks of interconnected highly protected marine areas is one way of increasing population resilience and halting the long-term loss of biodiversity in the oceans. In this study, we evaluated the efficiency of systematic conservation planning (SCP) varying their adequacy level. Conservation plans with objectives of conserving 10% and 30% of the fragmented hard bottom habitat surface were established by crossing current pressures in the Gulf of Lion (NW Med Sea) with three types of connectivity : (i) structural connectivity (ii) early summer and (iii) late summer connectivity estimated from larval dispersal modeling, according to the reproductive traits of two umbrella species, the gorgonians Eunicella singularis and Leptogorgia sarmentosa. The efficiency of each conservation plan in protecting populations in the Gulf of Lion was then assessed against independent observations of the spatial distribution of the two species. When functional connectivity replaced structural connectivity, the spatial distribution of highly protected areas was significantly modified targeting sites in the central Gulf of Lion, and the efficiency (ratio of proportion of individuals under protection to protection cost) increased by 300 % (20 %, respectively) in the objective of conserving 10% (respectively, 30%) of the hard bottom habitat surface. Moreover, SCP was more focussed when functional connectivity replaced structural connectivity, showing that using functional connectivity is all the more important that the conservation target is low. This study illustrates as well the potential for trait-based estimates of functional connectivity arising from larval dispersal.