Staurophora amphioxys

The specimens of Staurophora amphioxys pictured on this website are from Brush Lake, a deep clear lake in the prairie pothole region of northeastern Montana (photos below). On the date of collection, Brush Lake had the following water quality characteristics: conductivity = 5760 µmhos/cm; pH = 9.30; total alkalinity = 1350 mg/L CaCO3; total hardness = 1168 mg/L equivalent CaCO3; Kjeldahl nitrogen = 1.3 mg/L; total phosphorus = 0.018 mg/L; dissolved oxygen = 7.50 mg/L; temperature = 18 C; CO3 = 1070 mg/l; SO4 = 2210 mg/L; Cl = 72.3 mg/L.

In Brush Lake, S. amphioxys is part of a remarkable diatom association that includes Scoliopleura peisonis, Surirella crumena, and other brackish-water species that are typical of coastal waters and inland waters of higher conductivity. Witkowski et al. (2000) report S. amphioxys as a “marine to brackish-water species widespread on European coasts of the Atlantic Ocean, found also in the Baltic Sea”. Hustedt (1959) reports it as a "mesohalobe, euryhaline salt water form, widely distributed and not rare in European coastal areas". The Brush Lake diatom flora may be a relict of the flora that populated the shallow inland sea that covered much of the Great Plains until about 55 million years ago.