Integrated taxonomic identification of ichthyoplankton samples by DNA metabarcoding in the Menorca Channel (Western Mediterranean Sea)

Abstract

Morphological identification and DNA metabarcoding (COI, 12S) were used to characterize the taxonomic composition and the structure of an ichthyoplankton spring assemblage in the Menorca Channel (Western Mediterranean Sea). We sampled 22 stations along six transects across the Channel with 300 m nets fitted to a Bongo plankton sampler. The COI marker was able to detect more taxa (66 at genus or species level) than the 12S marker (41 taxa) or morphologic taxonomy (46 taxa). The abundance of 16 taxa with high visual counts (≥10 ind./10 m2) and high occurrence (≥50% of samples) in the morphological taxonomic data set correlated well with high number of assigned sequences of the genetic marker COI; for instance, for Cyclothone braueri, Lampanyctus crocodilus, Spicara smaris or Engraulis encrasicolus. Integrating morphological taxonomy and DNA metabarcoding provided a complete and accurate picture of the ichthyoplankton community. This assemblage was rich in species (90 taxa, of which 84 identified at genus or species level) and was composed of a majority of locally-spawned benthopelagic species, along with 18 mesopelagic species (mostly Myctophidae and Gonostomatidae). The multivariate analysis of the species assemblage suggests that sea floor habitat type (presence of rhodolith beds) and water masses play an important role in the spatial distribution of ichthyoplankton in the Menorca Channel.