Phytoplankton community structure in the Goro lagoon analyzed by microscopy and molecular approaches

Fondo, Joyce Rukia

http://hdl.handle.net/10400.1/19845

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Authors

Fondo, Joyce Rukia

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Abstract(s)

This study aimed at investigating the phytoplankton dynamics in a coastal lagoon with complex hydrological dynamics (Sacca di Goro, Northern Adriatic Sea, Italy) highly utilized for shellfish farming, by combining a morphological approach (microscopy) with the innovative eDNA metabarcoding, towards a more informed management of transitional areas. A monthly sampling was carried out between September 2020-2021 in 4 sites. Both the molecular and morphological method resulted valid tools for phytoplankton monitoring. Seasonal variation in phytoplankton abundances and high densities during spring dominated by diatoms (Chaetoceros, Skeletonema, Pseudo-nitzschia, and Cyclotella spp.) were found. Differences in taxa identification between the two methods were observed, as 147 and 158 taxa were reported using the morphological and molecular approach respectively. Although eDNA resulted efficient in detecting cryptic taxa and picophytoplankton that were not morphologically identified, limitations were reported in resolution at species level, in quantification and in identification of some groups (Cyanobacteria and Euglenophyceae), due to the lack of representative sequences in current databases. Potential HAB species were found at low densities (dinoflagellates: Prorocentrum cordatum, Gonyaulax sp., Alexandrium sp., Heterocapsa sp., and diatoms: Pseudo-nitzschia delicatissima and seriata complex) which could be threats to shellfish farm and human health. The study highlights the value of implementing monitoring programs using innovative tools (e.g., eDNA) to analyse the phytoplankton diversity and identify toxic species. Due to the sensitivity of transitional ecosystems, combining different approaches, such as microscopy able to quantify phytoplankton at low taxonomic level and a fast and powerful molecular tool, could be fundamental to assess the composition and ecological function of microalgal communities and facilitate a better conservation strategy in view of climate changes.