by Xavier Turon
In November, 2015, Manuel Orobitg, student of the Master of Ocenagropahy and Management of the Marine Environment at the University of Barcelona, presented his MSc Thesis “
Morphology vs metabarcoding. A comparison of techniques for biodiversity assessment in Maërl beds”, supervised by Xavier Turon, Creu Palacin and Owen Wangensteen. This Thesis reported results from the
Metabarpark project, with which the ChallenGen project is closely collaborating.
 |
| Sampling of the Maërl community in Islas Cíes. |
 |
| Assortment of crustaceans from the 1 mm fraction. |
In this study, Manuel analysed morphologically samples collected at the same time as the ones for the genetic studies in the detritic bottoms of Islas Cies and Cabrera Archipelago. He focused his analyses on three major groups: polychaetes, crustaceans, and molluscs. He identified at the lowest level possible, with the help of taxonomists (a big thanks goes to Daniel Martin and Lídia Delgado) the species present in the 10 mm and 1 mm filtrates, and obtained biomass values by weight. The morphological analyses found 77, 45, and 44 morphospecies of polychaetes, crustaceans, and molluscs, respectively, while the genetic analyses yielded 182, 245, and 70 MOTUs, respectively, for the same size fractions. Thus, metabarcoding allowed the determination of a higher diversity, but the taxonomic precision attained was higher with morphology. On the other hand, all structural parameters (biomass dominance curves, alpha- and beta-diversity patterns) were markedly different between the metabarcoding and the morphology datasets, indicating that both methods capture different aspects of the biodiversity structure present. The morphological datasets tended to be quantitatively dominated by a few species, while metabarcoding found a more even distribution of biomass of the dominant MOTUs.
