Diatoms of the northeastern Gulf of Mexico: Vallithidium (Achnanthales: Achnanthidiaceae), a new monoraphid genus based on Navicula marginulata Cleve

Abstract

While conducting a systematic investigation of phytoplankton assemblages in the northeastern Gulf of Mexico (GOM) in the aftermath of the Deepwater Horizon blowout we took the opportunity to collect sediment samples from off the coast of Pensacola Bay, Florida. These samples contained sufficient numbers of a monoraphid diatom initially identified as Achnanthes controversa Hustedt (Navicula marginulata Cleve) to examine its fine structure in detail. The results of these investigations clearly show that this taxon could not be accommodated in Achnanthes as currently understood, or in any currently described genus in the Achnanthidiaceae. We, therefore, propose a new genus, Vallithidium, with Vallithidium marginulatum (Cleve), J.A. Nienow & A.K.S.K Prasad as the generitype. Our investigations also show that the taxon Hustedt illustrated from Campeche Bay is not the same as the taxon described from the northeastern Gulf. We therefore describe it as a separate species in the new genus, Vallithidium campechianum sp. nov.