“Relationship between Environmental Factors and Aquatic Macrophyte Distribution in the Old Ausable River Channel” Johan Wiklund, M. Sc. Thesis, Univ. Western Ontario.  All photos © Johan Wiklund 

Wolffia sp and Lemna minor 
bloom covering water surface

Chara vulgaris  
Looking down upon a stand

Chara vulgaris meadow

There are 29 species of large aquatic vegetation located in the Old Ausable River Channel. Six of these species dominate certain sections of the river. The six species include: Chara vulgaris, Elodea canadensis, Myriophyllum spicatum, Vallisneria americana, Wolffia spp. and Lemna minor.

Wiklund (2001) showed that there are differences in aquatic vegetation above and below the dam in the Pinery. 

Above the dam, the dominant species is Chara vulgaris, a plant species that creates a dense mat 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. 

Above the dam, closest to Grand Bend two species, Wolfia spp. and Lemna minor become very abundant later in summer and cover the water surface (looks like algae bloom on surface).

Elodea canadensis
seen up close growing in shallow water

Myriophyllum spicatum 
forming a floating canopy

Vallisneria americana

Below the dam in the Pinery, the turbidity of the water in the channel increases. As well, the water conditions in this section of the channel are heavily influenced by the Ausable River Cut. The water from the “Cut” is higher in nutrients primarily because of inputs from agricultural land base.  Therefore, we observe two plant species that thrive under these conditions: 

Elodea canadensis is dominant where sediments are rich in nutrients. 

Myriophyllum spicatum becomes abundant where sediments have low to moderate ammonium content. 

Vallisneria americana dominates near the confluence with the Ausable River Cut due to the increased velocity and turbidity of the water in this area.

Johan’s research on the sediments of the Old Ausable River Channel concluded that the centre of the channel is filling in with sediment. This is expected due to the slow flowing nature of the present channel. When there is no flow to carry the particles, they fall out of suspension and settle at the bottom of the river.

All photos © Johan Wiklund