Eunotia incisa

Eunotia incisa is common in acidic, low nutrient, freshwater environments ranging from bryophyte epiphytes to ponds and small lakes, and can occasionally occur in high abundances (Patrick and Reimer 1966, Camburn and Charles 2000, Siver et al. 2011, Krammer and Lange-Bertalot 1991). Populations are often noted to contain several forms suggesting additional studies are warranted in this group (Krammer and Lange-Bertalot 1991, Siver et al. 2005, Peeters and Ector 2018).

North American populations of Eunotia incisa have been illustrated and reported from several microhabitat types in the Carolina Bays (Gaiser and Johansen 2000) and common as a Fontinalis epiphyte in Long Branch Creek (Camburn et al. 1978), South Carolina. Furey et al. (2011) found it in moderate to high abundance as epiphytic on bryophytes in 1^st-5^th order streams below 1605 masl in the Great Smoky Mountains National Park. Camburn and Charles (2000) report it from sediment cores taken in New York and Adirondack lakes. Bahls (2011) illustrated populations of Eunotia incisa from small ponds and lakes in Montana and Washington. Reavie and Kireta (2015) report it in protected wetlands in the Laurentian Great Lakes especially around Lakes Superior, Michigan, and Ontario. In the Great Lakes Network National Parks, it is found as rare in sediment samples form many GLKN lakes, but notably common in Outer Lagoon (Apostle Isands National Lakeshore) and Shoepack Lake (Voyageurs National Park). In the eastern US, E. incisa is reported as two forms from acidic oligotrophic ponds on Cape Cod, Massachusetts Siver et al. (2005), and from a few acidic and oligotrophic waterbodies on the Atlantic Coastal Plain (Siver and Hamilton 2011).

In Canada, Eunotia incisa is widely reported from stained softwater lakes in Quebec and Labrador (Fallu et al. 2000) and rivers in Quebec (Lavoie et al. 2008).

Many groups have used Eunotia incisa as an indicator organism and published regional environmental optima, including:

Gaiser and Johansen (2000): pH 4.6, water depth 17 cm

Reavie and Kireta (2015): TP 25 µg/l, Cl- 10 µg/l

Camburn and Charles (2000): pH 5.21, ANC 12 µeq/l, TP 6.28 µg/l

Furey et al. (2011): Found between pH 3.9-5.6.

Siver et al. (2005): the common form optima of pH 5.2, TP 11.2; the narrow form pH 5.2, TP 10.8

Siver and Hamilton (2011): pH 5.3, TP 12.9

Fallu et al. (2000): DOC opt 10.5 mg/l, alk 22 µeq/l