• Category
  • Length Range
    17-51 µm
  • Width Range
    4.6-7.5 µm
  • Striae in 10 µm
    18-28 dorsal, 19-28 ventral

Identification

Description

Valves are lanceolate and weakly dorsiventral. Apices are rounded and may be slightly protracted. The axial area is narrow. The raphe is lateral. Proximal raphe fissures are reverse-lateral and ventrally deflected. Terminal raphe fissures are filiform and are dorsally deflected. Striae are radiate throughout. Near the valve center, striae are more widely spaced. Areolae cannot be resolved under the light microscope.

The size and shape of the valves and width of the apices of Delicata alpestris are variable depending on habitat (see Autecology section). Of the three supposed morphotypes of this taxon from Montana, the one chosen to represent it here, from Belly River, Glacier National Park, is the one most similar to the type population from the Austrian Alps.

Autecology

Delicata alpestris is found in springs, streams and mossy seeps at higher elevations in western Montana. Valve size and shape and the width of the apices are highly variable depending on habitat. Three such morphotypes are shown below. Genetic analysis may prove these forms to be separate taxa, but for now they fit under the rather wide morphological range of D. alpestris.

The name "alpestris" signifies alpine habitats. The taxon was originally described from the Lechtaler Alps in the Austrian Tyrol. The morphotype from Montana that most closely resembles the type population was collected from a river in Glacier National Park. Another Montana morphotype was also collected from Glacier, this one from mossy seeps at the foot of Jackson Glacier, one of the few remaining alpine glaciers in the park.

*Delicata alpestris* Morphotypes
Credit: Loren Bahls
Three morphotypes of Delicata alpestris from mountain habitats in western Montana.
Jackson Basin Site 1
Credit: Tara Luna
Mossy seep at the foot of Jackson Glacier in Glacier National Park, home of Delicata alpestris.
Jackson Basin Site 2
Credit: Tara Luna
Mossy seep at the foot of Jackson Glacier in Glacier National Park, home of Delicata alpestris.

Original Description

Differs from the nominate variety by valve ends broader protracted, valves broader up to 6.7 µm, structure coarser with 15-18 striae/10 µm.

  • Basionym
    Delicata delicatula var. alpestris
  • Author
    Krammer 2003
  • Length Range
    35-48 µm
  • Width
    4.4-6.7 µm
  • Striae in 10µm
    15-18

Original Images

Delicata Alpestris Origimag001
Delicata Alpestris Origdesc001

Cite This Page

Bahls, L. (2017). Delicata alpestris. In Diatoms of North America. Retrieved October 17, 2019, from https://diatoms.org/species/delicata_alpestris

Responses

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