Aulacoseira ambigua

This taxon is reported to be widespread in freshwater (Foged 1981, Cox 1996). Originally described from Belgium (Grunow 1882), in North America this taxon has been reported from lakes in the northeastern US (Camburn and Charles 2000, Siver et al. 2005), Virginia, Georgia, South Carolina (Bishop et al. 2017), the western US (Bahls 2021), Alaska (Foged 1981) and Ohio (Collins and Kalinsky 1977). Colonies are found in the plankton of 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 and Hamilton 2011), although it has also been reported from the plankton of rivers (Hansmann 1973, Bahls 2021). Reavie and Kireta (2015) report it to be a very weak indicator of moderate stress.

In the Great Lakes National Parks (Edlund et al. 2011, 2012, 2013), this taxon 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 it 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 this taxon as an indicator organism and published regional environmental optima and tolerances including:

Camburn and Charles (2000): Abundance Weighted Mean (AWM) pH – 6.47 +/- 0.77 AWM Acid Neutralizing Capacity – 76 +/- 122 µeq/L, AWM Total Al – 72 +/- 85 µg/L, AWM Dissolved Organic Carbon – 207 +/- 174 µmol/L, Total Phosphorus (TP) – 14.3 +/- 0.8 µg/L for populations from low alkalinity lakes of the American Northeast.

Reavie and Smol (2001): TP – 0.016 mg/L, pH – 8.14, Total Nitrogen – 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 µg/L 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 – 0.170 mg/L TP – 6 µg/L for populations from the Rocky Mountains, Cascades Range, Sierra Nevada Mountains, and the Great Plains.