There are 29 species of large aquatic vegetation located in the Old Ausable Channel. Six of these species dominate certain sections of the river:
AQUATIC PLANT SPECIES
Common Stonewort is the most dominant aquatic plant upstream of the Pinery Park dam, growing in dense mats on the bottom of the river. This species is present due to the low turbidity and bicarbonate-rich groundwater that feeds the system in this section of the river.
Wolffia sp. and Lemna minor
Duckweeds such as Wolfia spp. and Lemna minor can become so plentiful in summer that it can cause the appearance of an algae bloom on the surface. This is most common in the areas nearest to Grand Bend.
Canadian Waterweed is dominant where sediments are rich in nutrients, so it is found more commonly downstream of the park dam due to turbidity increases in the water.
Eurasian Water-milfoil is an aggressive invasive species that is predominately found where sediments have low to moderate ammonium content. Learn more about invasive species in the OAC.
Water Celery dominates near the confluence with the Ausable River Cut due to the increased velocity and turbidity of the water in this area.
Source: “Relationship between Environmental Factors and Aquatic Macrophyte Distribution in the Old Ausable River Channel” Johan Wiklund, M. Sc. Thesis, Univ. Western Ontario. All photos above © Johan Wiklund