Gyrosigma fasciola Griffith et Henfrey

Gyrosigma fasciola (Ehrenberg) Griffith et Henfrey (Figure 80)

Literature: (Al-Handal and Wulff 2008a, p. 54, figs. 101, 130– 131; Krammer and Lange-Bertalot 1986, p. 300, fig. 116.6).

Description: Length 97–140 µm, width 11–14 µm, transverse striae 21–24 in 10 µm.

Remarks: One of the most common benthic diatoms in Potter Cove. It forms a thick diatom film in some places.

Ecology and distribution: A marine and brackish-water species of worldwide distribution but more frequent in the marine littoral of the Atlantic and the North Sea (Jahn et al. 2005). Reported from the Arctic (Cardinal et al. 1986; von Quillfeldt 2000). Common in Potter Cove.

Description: Length 85–90 µm, width 13–14 µm, striae not resolved under LM.

Remarks: This species has rarely been described in recent literature but is mentioned only in diatom checklists from Europe and North America (e.g., Hendey 1974; Mather et al. 2010) and is mostly referred to as G. fasciola var. arcuata (Donkin) Cleve. The species can be easily distinguished from G. fasciola by its shorter and strongly arcuate valve poles. Jahn et al. (2005) typified this species and separated it from G. fasciola.

Ecology and distribution: It is difficult to trace the distribution of this species as in many records it might have been confused with G. fasciola. It does not seem to have been reported from Antarctica even in its varietal rank but was observed in the sub-Arctic (Cardinal et al. 1986 as var. arcuata). The species has not been observed in previous samples from Potter Cove. Rare in the present material.