• Category
  • Length Range
    48-53 µm
  • Width Range
    9-10 µm
  • Striae in 10 µm
    8-9 at the center, 11-12 towards the apices

Identification

Description

Valves are lanceolate with elongate-protracted, rounded apices. The axial area is narrow, straight, widening to form an irregularly-rounded to elliptical central area. The central area is formed by shortened striae that are also more widely spaced than elsewhere on the valve. The raphe is lateral, slightly arched, with dilated proximal raphe ends. Striae are distinctly lineolate, radiate around the center, becoming parallel, then convergent at the ends.

Taxonomic note: We present N. rhynchocephala following Lange-Bertalot (2001). The specimen illustrated as N. rhynchocephala in Patrick & Reimer (1966) corresponds to our treatment of N. rhynchotella. The type material of N. rhynchocephala, however, has not been investigated and further work may clarify the original type as designated.

Autecology

Reported to be widespread in freshwater (Patrick and Reimer 1966, Hansmann 1973, Foged 1981, Cox 1996). In North America this taxon has been reported from Alaska (Foged 1981), Utah (Grimes and Rushforth 1982, Bateman and Rushforth 1984), Quebec (Reavie and Smol 1998) Cape Cod (Siver et al. 2005), Virginia, South Carolina (Bishop et al. 2017), and all states and ecoregions in the northwest (Bahls 2021). This taxon is reported to occur in rivers, streams (Bahls 2021), ponds (Siver et al. 2005), and lakes (Grimes and Rushforth 1982, Bateman and Rushforth 1984). Bahls (2021) reported that this taxon mostly occurs in the mountains.

In the Great Lakes National Parks (Edlund et al. 2011, 2012, 2013), this taxon is common (1-10% relative abundance) in sediment core material from lakes in Sleeping Bear Dune (Shell and Bass lakes) and Isle Royale (Ahmik Lake).

Reported to prefer alkaline waters (Sovereign 1958, Foged 1981, Siver et al. 2005, Novais et al. 2014, Bahls 2021). Most sources also report a preference for low to moderate conductivity (Foged 1981, Cox 1996, Bahls 2021); however, Patrick and Reimer (1966) reported it to be, “halophilous to indifferent to small amounts of chloride”, and Çelekli et el. (2018) report this taxon to be associated with elevated conductivity and nutrient content. Bahls (2021) reported this taxon to prefer waters with low to moderate nutrients. Cox (1996) reported this taxon to occur in β-α-saprobic conditions. Novais et al. (2014) reported that this taxon is indicative of permanent waterbodies, but also report it to occur in periodic water or wet subaerial habitats. Novais et al. (2014) also report this taxon to be indifferent to current and trophic state. Reavie and Andresen (2020) report this taxon to be a very weak indicator of moderate environmental stress in the Great Lakes.

Several research groups consider this taxon as an indicator organism and published regional environmental optima and tolerances including:

Sovereign (1958): pH 6.0-9.5 for populations from the pacific northwest.

Novais et al. (2014): Current Velocity – 0.57 m/s, range – 0.17-0.97 m/s, Temperature – 24.4°C, range 11.8-29.2°C, Conductivity – 210 µS/cm, range 65-616 µS/cm, pH – 6.7, range – 5.7-7.7, Dissolved Oxygen – 82.3%, range – 31.5-106.5%, Alkalinity – 43 mg/L, range – 25-157 mg/L, Calcium – 14.3 mg/L, range – 5.6-58.0 mg/L, Chloride – 34.1 mg/L, range – 9.9-163.8 mg/L, Hardness – 40 mg/L, range – 10-165 mg/L, Magnesium – 4.6 mg/L, range – 0.7-11.9 mg/L, Sodium – 4.3 mg/L, range - 0.7-13.1 for populations from Portugal.

Reavie and Andresen (2020): Total Phosphorus (TP) optima in excess of 30 µg/L, and Chloride optima between 10 and 50 µg/L for populations from the Great Lakes.

Bahls (2021): pH – 7.4, Conductivity – 685 µS/cm, Total Nitrogen – 1.140 mg/L, TP – 101 µg/L, Temperature – 13.9 °C for populations in the Northwest.

Original Description

  • Author
    Kütz. 1844

Original Images

N Rhynchocephala  Kutzing 1844

Citations & Links

Citations

Links

Updates

Nov 08, 2024 - Addition of Autecology

From 2011 until 2024 the autecological information on this taxon page was limited. As of this update, information on ecology, biogeography, and environmental optima have been added. - Lane Allen & Mark Edlund

Cite This Page

Kociolek, P., Allen, L., Edlund, M. (2011). Navicula rhynchocephala. In Diatoms of North America. Retrieved December 16, 2024, from https://diatoms.org/species/46400/navicula_rhynchocephala

Responses

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

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