Under the canopy: Community-wide effects of invasive algae in Marine Protected Areas revealed by metabarcoding
We analysed with multigene (18S and COI) metabarcoding the effects of the proliferation of invasive seaweeds on rocky littoral communities in two Spanish Marine Protected Areas. The invasive algae studied were Caulerpa cylindracea, Lophocladia lallemandii and Asparagopsis armata. They are canopy-forming, landscape-dominant seaweeds, and we were interested in their effects on the underlying communities of meiobenthos and macrobenthos, separated in two size fractions through sieving. A new semiquantitative treatment of metabarcoding data is introduced. The results for both markers showed that the presence of the invasive seaweed had a significant effect on the understory communities for Lophocladia lallemandii and Asparagopsis armata but not for Caulerpa cylindracea. Likewise, changes in MOTU richness and diversity with invasion status varied in magnitude and direction depending on the alga considered. Our results showed that metabarcoding allows monitoring of the less conspicuous, but not least important, effects of the presence of dominant invasive seaweeds ; This research was funded by projects Metabarpark and CORCLIM from the Spanish National Parks Autonomous Agency (OAPN 1036/2013 and 766S/2012), and ChallenGen CTM2013-48163 and ANIMA CGL2016-76341-R projects from the Spanish Government. OSW is currently funded by project SeaDNA, NE/N005759/1 grant from the Natural Environment Research Council (NERC)