• Category
  • Length Range
    11.2-82.7 µm
  • Width Range
    3.2-8.8 µm
  • Striae in 10 µm



Valves are linear with an inflation in the center of the valve and capitate to slightly capitate apices. The medial inflation of the valve is wider than the apices. Striae are usually parallel, but can be slightly radiate in the medial inflation. The striae are alternate. The axial area is narrow and linear. The central area is small and rhombic. Short marginal spines are present, although the spines are difficult to see in LM. The girdle bands are closed and have large septa. In addition to large septa, much smaller rudimentary septa can be observed in the girdle bands. The number of girdle bands varies per frustule; there can be any number from two to many. One rimoportula per valve is present, usually located near or within the central area. Cells are joined in colonies, usually in zig-zag or stellate formations. Frustules are rectangular in girdle view.

This taxon is highly variable in its morphology and its variability has been treated differently by different authors. Knudson (1952) described four varieties, based primarily on colony morphology. Koppen (1975), who many have followed for US taxonomy, separated T. flocculosa into three ‘strains’, based on size range and autecology. In Diatoms of the US, I include strains III, IIIp, and IV together in the concept of T. flocculosa.

For those interested in following Koppen (1975), strain III is distinguished by ends that are not distinctly capitate. The medial inflation widens gradually, usually to a width of 4.5-6.5 µm. Valves of strain III can be as long as 83 µm. Cells of strain III grow attached to surfaces, usually on rocks or macrophytes.

Strain IIIp appears nearly identical to strain III, except that valves can reach up to 122µm in length. Strain IIIp valves can also be slightly twisted. In addition, strain IIIp is planktonic.

Strain IV has capitate ends and the medial inflation widens abruptly to 7.5-8.5 µm. Strain IV is smaller than strain III, with a maximum length of 39 µm.


Tabellaria flocculosa var. flocculosa tends to grow in freshwater, slightly acidic to acidic waters, though it can have a wide pH tolerance (Hustedt 1930, Niels 1981, Round, Crawford and Mann 1990, Krammer and Lange-Bertalot 1991). It is commonly found in peat bogs, running water, or lakes. T. flocculosa is cosmopolitan and more common in northern latitudes (temperate to arctic regions). Strains III and IV grow attached to hard substrates or vegetation, while Strain IIIp is planktonic. Strains III and IV grow in zig-zag colonies of indeterminate length. Strain IIIp can grow in zig-zag or stellate colonies, but usually no more than 5 cells per colony.

Original Description

  • Basionym
    Conferva flocculosa
  • Author
    Roth 1797

Original Images

T Flocculosa Orig Illjpg
T Flocculosa Orig Desjpg

Cite This Page

DeColibus, D. (2013). Tabellaria flocculosa. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/tabellaria_flocculosa


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