Aulacoseira ambigua

This taxon is reported to be widespread in freshwater (Foged 1981; Cox 1996). Originally described from Belgium (Grunow 1882), verified reports from North America exist from lakes in the Northeastern US (Camburn and Charles 2000; Siver et al. 2005), the Western US (Bahls 2021), Alaska (Foged 1981) and Ohio (Collins & Kalinsky 1977). Reported to occur planktonically in oligotrophic (Bahls 2021), mesotrophic (Siver et al. 2005), and eutrophic waters (Cox 1996). This taxon appears to prefer large and deep waterbodies (Siver et al. 2005; Siver & Hamilton 2011), though it has been reported from the plankton of lotic systems as well (Hansmann 1973; Bahls 2021). Reavie & Kireta (2015) report this taxon to be a very weak indicator of moderate stress.

In the Great Lakes National Parks (Edlund et al. 2011, 2012, 2013), A. ambigua is very common (>10% relative abundance) in sediment core material from lakes in Isle Royale (Richie and Ahmik lakes), Voyageurs (Shoepack, Peary, Mukooda, Brown and Ek lakes), Sleeping Bear Dunes (Manitou Lake), and Pictured Rocks (Grand Sable and Beaver lakes).

This taxon prefers circumneutral to alkaline waters (Foged, 1981; Siver et al. 2005; Bahls 2021).

Foged (1981) describes this taxon as an “oligohalobe (indifferent)” suggesting that this taxon prefers low conductivity systems but is not particularly sensitive to conductivity. Bahls (2021) also states that this taxon prefers water with low conductivity.

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

Camburn and Charles (2000): AWM pH – 6.47 pH Tol – 0.77 AWM ANC – 76 µeq/L, ANC Tol – 122 µeq/L, AWM Total Al – 72 µg/L, Total Al Tol – 85 µg/L, AWM DOC – 207 µmol/L DOC Tol – 174 µmol/L, TP – 14.3 µg/L, TP Tol – 0.8 µg/L for populations from low alkalinity lakes of the American Northeast.

Reavie & Smol (2001): TP – 0.016 mg/L, pH – 8.14, TN – 0.469 mg/L, Max Depth – 19.4 m, Chla – 1.72 mg/L for populations from lakes in southeastern Ontario.

Siver et al. (2005): pH optima – 6.5 +/- 0.7, TP optima – 14.3 +/- 0.8 for populations from Cape Cod.

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

Bahls (2021): Conductivity – 100 µS/cm, pH – 7.6, Temperature 14.0 °C, TN – 170 µg/L TP – 6 µg/L for populations from the Rockies, Cascades, Sierras and Great Plains.