Platessa conspicua

This taxon has been widely reported from boreal habitats. Populations reported with light micrographs in North America are from British Columbia (Cumming et al. 1995), St. Lawrence River (Reavie and Smol 1998), Northern Alberta and the Northwestern Territiories (Moser et al. 2004), the Great Lakes (Reavie 2020), the Rocky Mountains, the Cascades Mountains, Coast Ranges, and Sierra Nevada Mountains (Bahls 2021). This taxon is known to occur in mountain streams, lakes, and wetlands (Bahls 2021).

In the Great Lakes National Parks (Edlund et al. 2009, 2011, 2012, 2013), this taxon is widely distributed but rare at Voyageurs (Cruiser), Isle Royale (Ahmik, Harvey), Sleeping Bear Dunes (Manitou), Pictured Rocks (Grand Sable) and the St. Croix National Scenic Riverway (Lake St. Croix).

Reported to prefer cool alkaline waters with low levels of nutrients and conductivity (Bahls 2021). This taxon is reported to be a strong indicator of moderately stressed ecosystems (Reavie 2020).

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

Wilson et al. (1994): Optimum Salinity – 0.13 g/L, Range - 0.03 – 0.53 g/L from the Interior Plateau of British Columbia.

Cumming et al. (1995): Optimum Total Phosphorus (TP) – 9.2 µg/L, TP range – 4.3 - 20.0 µg/L, optimum salinity 0.13 g/L, range – 0.03 – 0.53 g/L from lakes in British Columbia.

Reavie and Smol (2001): TP – 18 µg/L, pH – 8.15, Total Nitrogen (TN) – 0.494, Maximum Depth – 18.4 m, Chlorophyll a – 1.78 mg/L from alkaline lakes in outheastern Ontario.

Ruhland et al. (2003): Dissolved Inorganic Carbon - 22.1 mg/L, TN – 0.878 mg/L, Dissolved Organic Carbon – 21.0 mg/L, Depth – 4.4 m, SiO₂ – 0.9 mg/L from lakes in the Central Canadian Arctic.

Moser et al. (2004): pH – 8.2, Conductivity – 235 µS/cm from boreal forest lakes in Northern Alberta and the Northwest Territories.

Reavie (2020): Report the optimum TP to be between 10 and 30 µg/l, and optimum Cl to be below 10 µg/l from the Great Lakes.

Bahls (2021): pH – 7.6, Conductivity – 140 µS/cm, Temperature – 12.8 °C, TN – 0.250 mg/L, TP – 84 µg/L for populations from the Rocky Mountains, the Cascades, Coast Ranges, and Sierras.