Fragilaria vaucheriae

Colonies may be benthic, forming palisade colonies attached to substratum by one end, attached singly to substratum by a mucilage pad (Morales 2010), or they may be planktonic.

This taxon has been reported to be widely distributed in freshwater (Patrick and Reimer 1966, Hansmann 1973, Lawson and Rushforth 1975, Clark and Rushforth 1977, Foged 1977, Bahls 2021). Bahls (2021) reported that this taxon is primarily found in streams and rivers but also occurs in other habitats, a statement supported by Hansmann (1973), Lawson and Rushforth (1975), and Clark and Rushforth (1977). It may, at times, be abundant in collections (Hansmann 1973, Lawson and Rushforth 1975). Clark and Rushforth (1977) reported it to be one of the most abundant and widely distributed taxa in their study, and state that “it pulsed several times at Henry’s Lake outlet”. In North America this taxon has been reported from Ohio (Collins and Kalinsky 1977), Alaska (Foged 1981), lakes in Northeast US (Camburn and Charles 2000), Cape Cod (Siver et al. 2005), and the western US (Bahls 2021).

In the Great Lakes National Parks (Edlund et al. 2011, 2012, 2013), this taxon is not very common, but is found at >1% relative abundance from shallow lake sediment core material from Voyageurs (Mukooda Lake), Isle Royale (Ahmik Lake), Pictured Rocks (Beaver and Grand Sable lakes), and Sleeping Bear Dunes (Bass and Florence lakes).

This species appears to be a generalist; Patrick and Reimer (1966) simply state, “Fresh water, seems to prefer cool water”. Foged (1981) remarked “Oligohalobe (indifferent) pH circumneutral (?)” regarding populations from Alaska. Cox (1996) stated, “Apparently wide ecological range; not clearly defined”. Siver et al. (2005) reported that this taxon displays a preference for alkaline waters of moderate to high nutrient content. Bahls (2021) also indicated that this taxon prefers alkaline waters but reported that populations in the northwestern US prefer low to moderate nutrient content and conductivity.

Many research groups have used this taxon as an indicator organism and published regional environmental optima and tolerances including:

Sovereign (1958): pH 7.0, pH tolerance – 6.0-9.0 for populations in the Pacific Northwest.

Blinn (1993): Specific conductance  – 16.5 mS, Mg⁺² – 24.9 µmol/L, Ca⁺² – 4.4 µmol/L, Na⁺¹ – 141.6 µmol/L, K⁺¹ – 12.2 µmol/L, CO₃^-2 – 44.5 µmol/L, HCO₃^-1 – 36.8 µmol/L, SO₄^-2 – 102.5 µmol/L, Cl^-1 – 49.2 µmol/L for saline lakes in western North America.

Camburn and Charles (2000): Abundance Weighted Mean (AWM) pH – 6.60 +/- 0.61 AWM Acid Neutralizing Capacity – 97 +/- 146 µeq/L, AWM Total Al – 189 +/- 93 µg/L, AWM Dissolved Organic Carbon – 390 +/- 214 µg/L, Total Phosphorus (TP) – 10.65 +/- 8.17 µg/L for populations from lakes in the Northeastern US.

Reavie and Smol (2001): TP - 17 µg/L, pH – 8.24, Total Nitrogen (TN) – 0.498 mg/L, Max Depth – 20.3 m, Chla – 1.82 mg/L for populations in southeastern Ontario. This taxon was treated as sensu lato in this publication.

Siver et al. (2005): pH optima – 7.2 +/- 0.4 TP optima – 15.4 +/- 3.8 µg/L

Reavie and Kireta (2015): Report a TP optima just below 30 µg/L and a Cl optima just over 10 µg/L for populations in the Great Lakes.

Bahls (2021): Conductivity – 320 µS/cm, pH – 7.6, Temperature – 12.9 °C TN – 490 µg/L, TP 69 µg/L for populations from the western US. Bahls stated that he treated this taxon as sensu lato in his analyses.