Nitzschia gobbii sp. nov. (Bacillariophyceae): a common but overlooked planktonic diatom species from the northwestern Adriatic Sea

ABSTRACT

Planktonic diatoms of the family Bacillariaceae, including Nitzschia spp, Pseudo-nitzschia spp and Cylindrotheca closterium, are common and often highly abundant in the Adriatic Sea. During the 30 years of phytoplankton monitoring at the coastal site of the LTER Senigallia-Susak transect, a nitzschioid diatom with morphology matching that of Nitzschia section Nitzschiella (dilated central portion and two long rostra) was frequently observed. In this study, we describe this new species as Nitzschia gobbii sp. nov., combining morphological (transmission electron microscopy and scanning electron microscopy) and molecular (LSU and ITS rDNA) data. The morphology of Nitzschia gobbii makes it easy to confuse with other common species in the Adriatic Sea (Cylindrotheca closterium and Pseudo-nitzschia galaxiae). The partial LSU rDNA sequences of strains of Nitzschia gobbii sp. nov. were resolved in a well-supported clade. In this area, this species has been mainly recorded in spring-summer with a maximum abundance of 3.2 × 10⁶ cells l^–1. None of the tested Nitzschia gobbii strains produced domoic acid in detectable amounts.

KEYWORDS:

• Diatom systematics
• ITS
• LSU
• LTER-site
• Phytoplankton
• Time series

ACKNOWLEDGEMENTS

The long-term monitoring has been carried in the framework of LTER-ITALY (Italian Long-Term Ecological Research Network) activities. The authors thank the Centro di Ricerca e Servizio di Microscopia delle Nanostrutture (CISMiN) of the Università Politecnica delle Marche for the Electron Microscopy service. Sincere thanks to the two anonymous referees for their valuable help in improving this manuscript.

SUPPLEMENTARY MATERIAL

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Additional information

Funding

This research was partially supported by the Italian Ministry of Health (Ricerca Finalizzata 2016) under grant number GR-2016-02363211 and by the EU 2014–2020 Interreg V-A Italy-Croatia CBC project ECOSS (Observing System in the Adriatic Sea: oceanographic observations for biodiversity) ID: 10042301. The cruises carried out with the M/N Actea were entirely funded by the Department of Life and Environmental Sciences (Università Politecnica delle Marche).