The MPA “Parc naturel marin d'Iroise” (France, Brittany), a zone of high conservation value for kelp forest biodiversity

Abstract : The MPA « Parc naturel marin d’Iroise » (PNMI) aims to know and protect the marine environment and promote sustainable maritime activities. In this MPA, kelps form large underwater forests that dominate the low intertidal to high subtidal zone and two kelp species are currently harvested: Laminaria digitata and Laminaria hyperborea. Our aim was to explore the conservation value of the PNMI regarding kelp forest biodiversity by characterizing and comparing this zone to other regions of Brittany regarding environmental conditions, genetic diversity of the two harvested kelp species and species diversity of seaweed communities living beneath the kelp canopy. We showed that, together with the Morlaix Bay, the PNMI constitutes a cold resilient water pocket surrounded by warmer and less resilient ones. The use of genetic tools revealed that both L. digitata and L. hyperborea populations exhibit high levels of genetic diversity within the PNMI and the Morlaix Bay; moreover, our results suggested that L. digitata populations in these two regions display unique genetic diversity and may have an exporting role to adjacent regions. The PNMI and the Morlaix Bay also displayed highly diverse seaweed communities and might constitute a refuge area from climate change for some red seaweed species.