• Category
  • Length Range
    32.0-43.3 µm
  • Width Range
    8.3-9.1 µm
  • Striae in 10 µm
  • Reported As
    Cymbopleura fluminea (Lange-Bertalot and Genkal 1999, p. 38, figs 56: 14-16)
    Cymbella naviculiformis var. linearis (Foged 1981, p. 73, plate L, fig. 8)
    Cymbopleura linearis (Krammer 2003, p. 58, figs 80: 1-11, 89: 1-11)



Valves are linear-lanceolate and slightly dorsiventral, with broadly rostrate to capitate apices. Dorsal margins are slightly convex; ventral margins are nearly straight. The axial area, near the median line of the valve, is narrow at the valve ends and widens gradually to merge with a rounded central area of variable size. The central area ranges in size from about one-fifth to four-fifths of the valve width. The raphe is lateral, becoming filiform to reverse-lateral at the proximal ends. The proximal ends are weakly expanded and deflected towards the ventral margin. Terminal raphe fissures are deflected dorsally. Striae are radiate, more widely spaced near the valve center, and very finely punctate. Areolae are difficult to resolve in LM.

This taxon displays considerable variation within a population in length to width ratio, shape of the ends, width of the axial area and width of the central area.

To prepare this taxon page, we compared populations in British Columbia, Saskatchewan, the north slope of Alaska, and Swedish Lapland, along with the iconotype image of Cymbella naviculiformis var. linearis Foged (=Cymbopleura linearis (Foged) Krammer). We conclude that C. linearis is a later, subjective synonym for C. fluminea Patrick and Freese.


Patrick and Freese (1961) described conditions at the type locality as follows: "seepage over silt-gravel surface", pH 6.7, temperature 18C, alkalinity 16 ppm (as CaCO3), hardness 30 ppm (as CaCO3), chloride 25 ppm, total iron (Fe) 0.07 ppm. Krammer (2003) reports both C. fluminea and C. linearis from oligotrophic waters with low electrolyte content. Besides several waters in Alaska, this species has also been reported from the subarctic region of Siberia (Lange-Bertalot and Genkal 1999), from Finnish and Swedish Lapland (Krammer 2003), and from a wet grassy meadow in northern Saskatchewan (photo below).

Sample 5 Overview
Credit: Beverly Boynton, Adventurers and Scientists for Conservation.
Wet grassy meadow near the Clearwater River in northern Saskatchewan, Canada: home of Cymbopleura fluminea.

Original Description

Valve with median raphe, but one margin is convex and the other is straight. Apices broadly rostrate. Axial area narrow, slightly widened into the central area. Central area small, linear. No isolated punctum or stigma present. Striae finely punctate, radiate. Striae 12-14 in 10 µ in the middle part of dorsal margin, 14-15 in 10 µ in middle part of ventral margin. On both sides of the raphe the striae to 18 in 10 µ at the apices. Length 34-40 µ. Breadth 6-8 µ.

  • Basionym
    Cymbella fluminea
  • Author
    R.M.Patrick and Freese 1961
  • Length Range
    34.0-40.0 µm
  • Width
    6.0-8.0 µm
  • Striae in 10µm
    12-14 middle/dorsal, 14-15 middle/ventral, up to 18 at the apices (dorsal and ventral)

Original Images

Cymbella fluminea orig illus 2
Cymbella fluminea HOLOTYPE
Cymbella fluminea HOLOTYPE
Cymbopleura fluminea orig descr

Cite This Page

Bahls, L, and Bogan, D, and Potapova, M. (2015). Cymbopleura fluminea. In Diatoms of North America. Retrieved July 21, 2018, from https://diatoms.org/species/cymbopleura_fluminea


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