• Category
  • Length Range
    45-78 µm
  • Width Range
    30-56 µm
  • Striae in 10 µm
    14-17 raphe valves, 14-22 rapheless valves

Identification

Description

Valves are broadly elliptic, with rounded apices. The valve length to width ratio is 1.3-1.7. The raphe valve has a hyaline marginal ring that separates a marginal area from an inner area. Striae are radiate. Striae in the central marginal area have many areolae, as compared to fewer marginal areolae at the apices. Striae in the marginal area are more widely spaced than striae in the inner area. Areolae are elliptic and somewhat disorganized near the valve center. Areolae number 14-16 in 10 µm for both the marginal and inner striae (measured at the hyaline band at middle of the raphe valve). The axial area is very narrow. The central area is small and rounded. The raphe is filiform and straight, with slightly inflated proximal ends.

The rapheless valve lacks a hyaline ring. The axial area is narrow. A central area is lacking. Striae are radiate. Areolae appear as short dashes and are arranged in zig-zag longitudinal rows. Areolae number 7-11 in 10 µm measured near the central area.

Our observations are based on specimens collected from a Pleistocene deposit near Terrebonne, Oregon. VanLandingham (1990) remarked that C. grovei became extinct during the Pleistocene epoch. We are uncertain that this species is extinct because the type locality of the Deschutes River suggests that this species may be extant.

We also observed specimens from other regions in the Northwest that share many of the features of C. grovei, but are much smaller in size. Further work is needed to determine if these represent separate, new species.

Autecology

The Pleistocene lacustrine deposit near Terrebonne also includes Cocconeis rugosa, Stauroneis acuta, and Stauroneis rex, taxa that are characteristic of relatively shallow soft-water environments.

Diatomite deposit, Terrebonne, Oregon
Credit: Rob Kimmich
Diatomite deposit near Terrebonne, Oregon. Collection site of Pleistocene Cocconeis grovei.
c-grovei-1
Credit: Image by Rob Kimmich. Slide by Raymond Hummelink of Neede, The Netherlands.
Raphe valve. Scale bar = 10 µm.
c-grovei-2
Credit: Image by Rob Kimmich. Slide by Raymond Hummelink of Neede, The Netherlands.
Raphe valve. Scale bar = 10 µm.
c-grovei-3
Credit: Image by Rob Kimmich. Slide by Raymond Hummelink of Neede, The Netherlands.
Rapheless valve. Scale bar = 10 µm.
c-grovei-4
Credit: Image by Rob Kimmich. Slide by Raymond Hummelink of Neede, The Netherlands.
Rapheless valve. Scale bar = 10 µm.

Original Description

Schmidt's Atlas (1894). Plate 194, Figure 3. Described from Deschutes River, Oregon.

  • Author
    A. Schmidt 1894

Original Images

Cocconeis Grovei A Schmidt

Cite This Page

Kimmich, R., Bahls, L. (2020). Cocconeis grovei. In Diatoms of North America. Retrieved September 26, 2021, from https://diatoms.org/species/cocconeis-grovei

Responses

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