Seminar Details

Species diversity and seasonality in the marine planktonic diatom Chaetoceros assessed by means of metabarcoding

Date

06/02/2020

Lecturers

Dr. Wiebe Kooistra - Dept. of Integrative Marine Ecology (IME), Stazione Zoologica Anton Dohrn, Italy

Abstract

Environmental DNA metabarcoding is proving to be a powerful approach to assess planktonic diatom diversity next to cell counting by means of LM. Here we examine the performance of 18S rDNA V4-metabarcoding in revealing the diversity in the diatom family Chetocerotaceae at the LTER-MC station in the Gulf of Naples. The LTER is located in the transition zone between near-shore water and the open sea. We analysed a metabarcode dataset collected on 48 sampling dates over 3 years, and assigned them to distinct species based on a phylogenetic analysis including named reference sequences from a database of taxonomically validated strains. Chaetocerotaceans resolved into a series of solitary haplotypes, each containing a modest number of reads, as well as a series of terminal polytomies composed of multiple haplotypes, each with usually one haplotype containing the vast majority of reads. Both the solitary haplotypes as well as the dominant haplotypes with their retinues of peripheral haplotypes were considered taxa. A total of 53 out of the 73 taxa included a reference, usually matching its solitary or dominant haplotype, and could thus be identified to the species-level. Distribution of the metabarcodes over the sampling dates revealed clear seasonal patterning with different species in cryptic species complexes found in offset periods. A comparison with contextual LM data showed that the species commonly recognized in the LM data were also present in the contemporary metabarcode data.

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