• Category
  • Length Range
    15-80 µm
  • Width Range
    4-7 µm
  • Striae in 10 µm
  • Synonyms
    Ceratoneis arcus (Ehrenb.) Kütz.



Valves are asymmetric to the apical axis; the dorsal margin is highly arched and convex, while the ventral margin is concave. A central, unilateral swelling is present on the ventral margin. Ghost striae may be present in the central swelling. Valve apices are capitate to attenuate. A narrow, distinct central sternum is present. One to two rimoportulae are present at the valve apices.


Hannaea arcus is found in cool flowing water in mountainous regions across the US.

Original Description

  • Basionym
    Navicula arcus
  • Author
    Ehrenb. 1836

Original Images

Navicula Arcus Orig Desc Text


Jul 19, 2024 - Citation correction

The transfer of Ceratoneis arcus (Ehrenberg) Kützing to Hannaea arcus Patrick 1961 was listed incorrectly as occurring in Patrick and Freese 1961. The transfer should appear as Hannea arcus Patrick (Patrick and Reimer 1966, pg. 132). - S. Spaulding

Cite This Page

Kociolek, P. (2010). Hannaea arcus. In Diatoms of North America. Retrieved July 19, 2024, from https://diatoms.org/species/hannaea_arcus


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Hannaea arcus 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.