Diatoms of the Northeastern Gulf of Mexico: Light and Electron Microscope Observations of Sulcatonitzschia, a new Genus of Nitzschioid Diatoms (Bacillariales: Bacillariaceae) with a Transverse Sulcus

• Published in: Gulf and Caribbean research 2021, Vol.32 (1), p.34-45
• Main Authors: Nienow, James, Prasad, Akshinthala
• Format: Article
• Language: English
• Subjects: Bacillariaceae; Blowouts; Colonies; Deep water; Diatoms; Electron microscopy; Fine structure; Fragilariopsis; Marine microorganisms; New genera; New genus; New species; Nitzschia; Offshore; Phytoplankton; Plankton; Ultrastructure
• ISSN: 2572-1410; 1528-0470; 2572-1410
• DOI: 10.18785/gcr.3201.06

During a systematic investigation of phytoplankton assemblages in the northeastern Gulf of Mexico (GOM) in the aftermath of the Deepwater Horizon blowout we encountered a population of diatoms morphologically similar to Nitzschia ossiformis (Taylor) Simonsen located about 75 km offshore and concentrated at a depth of 60—120 meters. The density of individuals in the population was sufficient to make detailed observations using light and electron microscopy. Our specimens were frequently united into short ribbon—like colonies. This, plus features of the fine structure of valve (biseriate striae, raphe canal without pores and flush with the valve surface) suggest the GOM population is more closely related to Fragilariopsis than to Nitzschia sensu stricto. The presence of a unique feature, described here for the first time, a transverse sulcus in the exterior surface of one of the poles, coupled with the characteristic shape of the valve, suggest our taxon cannot be accommodated in Fragilariopsis, or any other genus hitherto known within the family Bacillariaceae. We, therefore, propose a new genus, Sulcatonitzschia for this diatom and any other nitzschioid diatom with a transverse sulcus, with a new species, Sulcatonitzschia novossiformis as the generitype. Published descriptions suggest that some populations identified as Nitzschia ossiformis may be conspecific with S. novossiformis, but the type of N. ossiformis as delineated by Taylor is not. Examination of the fine structure of the valves is necessary to resolve these relationships.