Geissleria decussis | Species - Diatoms of North America

Category

Symmetric Biraphid
Length Range

16-30 µm
Width Range

6–9 µm
Striae in 10 µm

14-18

Contributor

Marina Potapova - Mar 2009
Reviewer

Sarah Spaulding - May 2010

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Identification

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Description

Valves are elliptical-lanceolate with rostrate to capitate apices, 6-9 µm wide and 16-30 µm long. The raphe is straight and filiform. Externally, the proximal raphe ends are surrounded by two small grooves. The axial area is narrow and linear. The central area is rectangular to irregular in shape, with an isolated stigma. Striae are uniseriate and radiate, becoming parallel or slightly convergent at the ends. The striae are also usually deflected, or bent, and number 14-18 in 10 µm. Short and long striae alternate in the central valve. Areolae are apically elongated and number approximately 60-70 in 10 µm. Subpolar areolae (annulae) are larger than the other areolae, forming two rows on either side of the raphe at the poles. Internally, the annulae are surrounded by spherical nodules, typical of the genus Geissleria.

Autecology

Fresh waters of moderate to high ionic strength

Size Range, µm3

101-1000
Motility

Moderately motile
Attachment

Unattached
Habitat

Benthic
BCG

BCG 4
Waterbody

Inland
Distribution

Western rivers 2004 Southeast rivers 2014 California coastal rivers 2017 Northeast lake sediments
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Original Description

Long. 16-22 µ, Lat.6-7 µ. Str. 16-20 in 10 µ, transverse lineatis. Valva elliptica, apicibus capitatis. Raphe directa, area hyalina angusta, media in parte valvae in aream transersam dilatata, cincta. Striis radiantibus, in apicibus convergentibus, mediis tribus longiudine diversa itaqve inter se remotis, ut amplificatione mediocre figura decussis existat. Nodulis terminalibus summis in apicibus situatis.

Basionym

Navicula decussis
Author

Østrup 1910
Length Range

16-22 µm
Width

6–7 µm
Striae in 10µm

16-20

Original Images

Citations & Links

Citations

Cite This Page

Potapova, M. (2009). Geissleria decussis. In Diatoms of North America. Retrieved December 16, 2024, from https://diatoms.org/species/44469/geissleria_decussis

Responses

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