Valves are lanceolate with rounded central margins and apices. Striae are radiate throughout the valve. The central area is asymmetrically rectangular and the axial area is broad and straight. Striae on one or both sides of the central area vary in length and are irregularly spaced. The striae are formed between internal costae giving a light interstriae and darker striae appearance in LM. The raphe is lateral, undulating and curving towards the proximal raphe ends. The proximal ends curve to one side of the central area. The distal fissures are scythe shaped. Areolae are distinct and round. A central nodule is evident. In girdle view the frustules are crescent shaped because of one convex and one concave valve face.


A brackish to highly alkaline species found from the type locality along the shoreline at the northern tip of Alaska. The pH of the lake is circumneutral with high levels of both calcium carbonate and sodium chloride.

Original Description

Navicula nunivakiana sp. nov. Pl. 2, Fig. 5

Valva lanceolata, attenuata ad apices rostratos, rotundatos aliquantulum. Area axiali angusta, distincta. Fissuris externis terminalibus raphis magna et versa in eodem cursu. Raphe undulata leniter. Area media inaequali in forma, transversa et asimili. Striis punctatis distincte et crasse, radiatis; paene parallelis inaequalibus in longitudine circum, aream mediam. Striis, 7-12 in 10 µ. Longitudo, 87-100 µ. Latitudo, 21-27 µ.

Valve lanceolate tapering toward the somewhat rostrate, rounded ends. Axial area narrow, distinct. External terminal fissures of the raphe large and turned in the same direction. Central area irregular in shape, transverse and asymmetrical. Striae distinctly and coarsely punctate, radiate; almost parallel and irregular in length about the central area. Striae, 7-12 in 10 µ Length, 87-100 µ. Breadth, 21-27 µ.

This species is distinguished by its slightly undulate raphe and the shape of the central area.

Occurrence in collection rare.

Specimen illustrated.-Station 116 (A-G.C. 8232) . Holotype.

Type locality.-Alaska, Sec. Jud. Div., Nunivak Archaeology Site, Barrow. Coll. L. R. Freese, 8 August 1951.

Distribution.—GEOGRAPHICAL—In addition to the type locality, specimens were found at Barrow Village, Freshwater Lake, Station 148, Coll. L. R. Freese, 18 August 1951 (A-G.C. 8262) . ECOLOGICAL Fresh water. Holotype from moss squeezings on slope of lagoon above high tide level. pH, 7.4. Other specimens from lake plankton. pH, 7.6; temp., 6° C ; alk., 23 ppm (as CaCO3) ; hardness, 50 ppm (as CaCO3) ; Cl, 58 ppm.

  • Author
    R.M.Patrick and Freese 1961
  • Length Range
    87-100 µm
  • Width
    21-27 µm
  • Striae in 10µm

Original Images

Nnunivakiana  Orig Ill Sm
Nnunivakiana  Orig Descr Sm

Cite This Page

Hamilton, P, and Manoylov, K. (2011). Navicula nunivakiana. In Diatoms of North America. Retrieved June 25, 2018, from


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Navicula nunivakiana from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.