Pseudostaurosira parasitica

This taxon is widespread (Foged 1981), with North American populations considered to conform to European populations (Morales et al. 2015). It has been reported (with light micrographs) in North America from Ohio (Collins and Kalinsky 1977), Alaska (Foged 1981), the northeastern United States (Camburn and Charles 2000), Québec (Fallu et al. 2000), Cape Cod (Siver et al. 2005), the Saint Lawrence River (Reavie and Smol 1998), the Great Lakes (Reavie and Kireta 2015), North Carolina (Bishop et al. 2017), British Columbia (Cumming et al. 1995), the Rocky Mountains, Great Plains, Sierra Nevada Mountains, and coastal streams of California (Bahls 2021).

In the Great Lakes National Parks (Edlund et al. 2009, 2011, 2012, 2013), this taxon is common (1-5% relative abundance) in Isle Royale National Park (Ahmik Lake) and is uncommon (<1% relative abundance) in the St. Croix National Scenic Riverway (Lake St. Croix).

Known to occur in cool, alkaline waters with moderate nutrients and conductivity (Patrick and Reimer 1966, Bahls 2021). Commonly observed as an epiphyte on other diatoms, particularly taxa in the genera Nitzschia and Surirella (Smith 1856, Patrick and Reimer 1966). Cells attach to a host via one of the ocellulimbi (Smith 1856, Morales et al. 2015).

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

Cumming et al. (1995): Total Phosphorus (TP) – 10.1 µg/L.

Fallu et al. (2000): Dissolved Organic Carbon - 9.72 +/- 1.55 mg/L for populations from Québec.

Reavie and Smol (2001): Total Phosphorus (TP) – 15 µg/L, pH – 8.22, Total Nitrogen (TN) – 0.426 mg/L, Max Depth – 16.3 m, Chlorophyll a – 1.82 mg/L.

Siver et al. (2005): pH – 6.6 +/- 0.8, TP – 15.2 +/- 6.5 µg/L for populations from low alkalinity lakes in the northeastern United States.

Reavie and Kireta (2015): Report an optimum TP just below 30 µg/L and an optimum chloride concentration just below 10 µg/L. They also report this taxon to be a weak indicator of moderate stress.

Bahls (2021): pH –7.7, Conductivity – 472 µS/cm, Temperature – 14.5 °C, TN – 0.580 mg/L, TP – 108 µg/L for populations from the Rocky Mountains, Great Plains, Sierra Nevada Mountains, and coastal streams of California.