Metabarcoding has proven an effective method for comprehensive biodiversity assessment. However, its application in biomonitoring requires the generation of time series data, which are mostly wanting. We have obtained COI metabarcoding datasets of benthic reef communities of the two marine National Parks established in Spain, one in the Mediterranean (Cabrera Archipelago), and the other in the Atlantic (Cíes Islands) coast. These sanctuaries are under stress as a result of invasive seaweeds and warming. We have sampled four (Cabrera) and three (Cíes) time points over a six-year span (2014-2020), analyzing five community-types in each Park, with and without invasive algae. We devised a method for direct sampling of the reef communities using quadrats and size-fractionation. The generation of time series required adjustments of the bioinformatics pipelines as the volume of data grew exponentially. We chose to reduce the datasets at each time point using a denoising procedure within samples that took into account the variability of each codon position in the coding sequences. These reduced datasets can be easily assembled, and clustered into molecular operational taxonomic units, at desired time points. Our results showed a highly diverse assemblage, with ca. 270,000 sequence variants that clustered into 35,543 molecular operational taxonomic units (MOTUs). The effect of invasive algae was overall minor, while a clear effect of time was detected at the last sampling date (2020), indicating ongoing changes. Our study proves the feasibility of biomonitoring benthic reef communities over time, and our survey will continue in the forthcoming years.

Primary Presenter: Xavier Turon, Consejo Superior Inv. Cientificas (xturon@ceab.csic.es)

Authors:

Xavier Turon, Centre for Advanced Studies of Blanes (CEAB, CSIC)  (xturon@ceab.csic.es)

Adrià Antich, Centre for Advanced Studies of Blanes (CEAB, CSIC)  (a.antich@ceab.csic.es)

Jesús Zarcero, Centre for Advanced Studies of Blanes (CEAB, CSIC)  (jzarcero@ceab.csic.es)

Creu Palacín, University of Barcelona  (cpalacin@ub.edu)

Owen Wangensteen, University of Barcelona  (owenwangensteen@ub.edu)