Metabarcoding reveals significant differences in communities with and without invasive seaweeds

While the data corresponding to the 2015 collecting trips are being analysed, we would like to share the first results concerning the communities sampled with and without invasive algae. In the Cíes Island, we compared the photophilous community with Cystoseira nodicaulis (natural assemblage) with equivalent communities with the introduced Asparagopsis armata. In Cabrera, we sampled in the same walls photophilous natural assemblages as well as communities dominated by Lophocladia lallemandii, while at deeper waters we sampled the natural sciaphilous community and Caulerpa cylindracea-dominated patches.

We identified with the gene 18S 2937 MOTUs in these communities. Our statistical analyses showed clear qualitative and quantitative differences between assemblages with and without the invasive seaweeds. While this was expected for the bigger size fractions, even for the smallest fraction (i.e., organisms between 1 mm and 65 microns) the differences were significant. This rich component of the biodiversity cannot be efficiently assessed with conventional methods, while genetic techniques have allowed its quantification and analysis.

Thus, metabarcoding revealed community shifts affecting even the small-sized meio-organisms (animals, algae, and protists) at very reduced spatial scales (tens of meters). The presence of invasive algae has therefore profound effects in community structure at all levels. This is one of the several interesting outcomes we are finding with our data, more soon!

This spatial representation (Multidimensional Scaling) allows the visualization of the differences between the sampled communities linked to the presence of invasive seaweeds