Brachysira arctoborealis

Wolfe and Kling 2001      Category: Symmetrical biraphid

REPORTED AS: Brachysira brebissonii morphotype latior (Lange-Bertalot and Moser 1994, p. 21, Tafel 42:1-4) | Brachysira brebissonii morphotype major (Lange-Bertalot and Moser 1994, p. 21, Tafel 43:2, 3) | Navicula serians var. minor (Grunow in Van Heurck 1880, plate XII, fig. 8) 

Boreozonacola olympica


Brachysira brebissonii

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - March 2014
Length Range: 22-48 µm
Width Range: 7.2-12.1 µm
Striae in 10 µm: 24-26


Valves are rhombic with broadly rounded apices. The axial area is narrow and straight, and bordered by a continuous column of areolae on each side. The central area is small and rhombic, sometimes with an enlarged isolated areola on one side. The raphe is filiform. Proximal raphe ends are weakly expanded. Distal raphe ends are difficult to see in LM. Striae are radiate and uniseriate. Areolae in the striae are transapically elliptic near the axial area and linear near the valve margins. Areolae are widely and irregularly spaced, creating a pattern of undulating longitudinal lines.

Note that valves displayed here from the Cascade Mountains in Washington attain a considerably larger size than those originally described from Canada.

Original Description

Author: Wolfe and Kling 2001
Length Range: 17-31 µm
Width Range: 7-10 µm
Striae in 10 µm: 19-25

Original Description

Original Images

Cite This Page:
Bahls, L. (2014). Brachysira arctoborealis. In Diatoms of the United States. Retrieved April 23, 2018, from

Species: Brachysira arctoborealis

Contributor: Loren Bahls

Reviewer: Marina Potapova


Lange-Bertalot, H. and Moser, G. (1994). Brachysira Monographie der Gattung. Bibliotheca Diatomologica 29: 1-212.

Shayler, H.A. and Siver, P.A. (2004). Biodiversity of the genus Brachysira in the Ocala National Forest, Florida, U.S.A. Proceedings of the Seventeenth International Diatom. Symposium Ottawa, Canada, 25th – 31st August 2002 (M. Poulin, ed.), Biopress limited, Bristol. p. 309-333.

Wolfe, A.P. and Kling, H.J. (2001). A consideration of some North American soft-water Brachysira taxa and description of B. arctoborealis sp. nov. Lange-Bertalot-Festschrift Studies on Diatoms, Dedicated to Dr. Dr. h.c. Horst Lange-Bertalot on the occasion of his 65th birthday.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Brachysira arctoborealis CAS

North American Diatom Ecological Database (NADED)

NADED ID: 18044

Autecology Discussion

Brachysira arctoborealis has been recorded from three lakes in the North Cascade Mountains of Washington. Water quality data are not available, but these lakes are presumed to have cold water, low pH, and low dissolved solids. The species was described from a lake on Baffin Island, Nunavut Territory, and also found in soft-water lakes of the Experimental Lakes Area in western Ontario, Canada (Wolfe and Kling 2001). It was reported by Shayler and Siver (2004) from soft-water lakes in Florida and by Lange-Bertalot ad Moser (1994) from Borneo and the Canadian Rockies (as B. brebissonii morphotype latior and B. brebissonii morphotype major, respectively). Wolfe and Kling (2001) suggest that it is probably a cosmopolitan species, much like B. brebissonii and B. microcephala.


Nada Lake, Chelan County, Washington: home of Brachysira arctoborealis.

Credit/Source: Ryan Davis, Adventurers and Scientists for Conservation