Description
An excellent shoreline marsh complex on the Bothwell Sand Plain, offering the best representation of a cattail marsh and meadow marsh complex with a beach barrier. Only a small remnant of formerly extensive marshes remain (Eagles & Beechey, 1985).

East shore marshes of Lake St. Clair (Eagles & Beechey, 1985):
An extensive and ecologically important system of marshes lie along the east shore of Lake St. Clair. These marshes are of international importance for their vital support of numerous waterfowl species during spring and fall migrations. They provide habitat for an appreciable number of rare, vulnerable or endangered species of plants and animals. This mash system is a remnant of a pattern of biotic communities once common in the region but now greatly reduced in extent. The area is large, has a high diversity of species, and is near to another significant marsh system, Walpole Island.

Vegetation
Vegetation types represented here include cattail marsh, reed marsh, meadow marsh, submerged aquatic communities, wooded swamp, and barrier beach communities. These are interspersed with a few pockets of open water (Klinkenberg, 1984 in Eagles & Beechey, 1985).

The St. Clair NWA contains examples of three major habitat types of the Lake St. Clair east shore marsh system: continuous emergent marsh; emergent marsh interspersed with small ponds, bays and channels; and open water marsh. Emergent marsh habitats are predominantly cattail stands, interspersed with a few meadow complexes of sedges with Phragmites patches. The cattail is usually dense, but other plants that occur within it include Lythrum salicaria, Impatiens biflora, and Carex stricta. Wet meadows occur on slightly higher ground within the marsh and host a variety of plant species (Eagles & Beechey, 1985).

Emergent marshes interspersed with small ponds provide sheltered aquatic habitats. These water areas have stands of aquatic emergents other than cattail and cover about 40% of St. Clair NWA. They contain a mosaic of species, with the principal elements being Pontederia cordata, Scirpus acutus, Scirpus validus, Sparganium spp., and Nymphaea tuberosa. Submergents include Chara sp., Vallisneria americana, Anacharis canadensis, Potamogeton spp., Myriophyllum spp., and Ceratophyllum demersum. Recent cattail and water level control measure have increased areas of open water with submergent vegetation (Eagles & Beechey, 1985).

Marsh zones that are open to Lake St. Clair vary in character as lake levels change. In some areas, large increases in the amount of quality waterfowl foods such as Sago Pondweed (Potamogeton pectinatus) and Wild Celery occurred when high lake levels killed extensive beds of emergent vegetation, largely cattails. Some extensive submerged beds of muskgrass occur. St. Clair NWA has a small area of open water marsh, where floating mats of Greater Burreed (Sparganium eurycarpum), Hardstem Bulrush, Tussock Sedge and Purple Loosestrife dominate, and other vegetation includes Tuberous Water Lily, Spatterdock (Nuphar advena var. variegatum) and cattail (Eagles & Beechey, 1985).

Representation
This wetland site offers excellent representation of shallow shoreline marsh complexes of the Bothwell Sand Plain (Kinkenberg, 1984 in Eagles & Beechey, 1985).

Landform
Lake St. Clair is a shallow, mesotrophic link in the Great Lakes system. Waters from Lake Huron flow in via the St. Clair River and out the Detroit River to Lake Erie. A major tributary, the Thames River, drains a 3500 sq. km watershed of southern Ontario lands, mostly in agricultural use. As the river approaches St. Clair, it crosses flat clay plains; between Chatham and the lake, the river drops less than 0.01m/km. The shallow Thames River channel has been extensively dyked to control the frequent spring flood waters, and little natural wetland habitat remains along the river flood plain. The lakeshore marshes lie on stratified clays combined with a series of sandy beach ridges formed long ago by lake wave action. There is an overlying deposit of organic materials from decayed marsh vegetation. The clay plains are among the most fertile in Canada. The rich soils once supported tall grass prairies and now produce fertile marshes or high yields of agricultural crops (Eagles & Beechey, 1985).

References

• Allen, G.M., P.F.J. Eagles and S.D. Price (eds.) 1990. Conserving Carolinian Canada: Conservation Biology in the Deciduous Forest Region. University of Waterloo Press, Waterloo. 346 pp.
  
  
• Eagles, P.F.J. and T.J. Beechey (eds.) 1985. Critical Unprotected Natural Areas in the Carolinian Life Zone of Canada. Final Report, Identification Subcommittee, Carolinian Canada. The Nature Conservancy of Canada, The Ontario Heritage Foundation and World Wildlife Fund (Canada). 400 pp.
  
  
• Klinkenberg, R. 1984. Life Science Areas of Natural and Scientific Interest in Site District 7-1: A Review and Assessment of Significant Natural Areas in Site District 7-1. Ontario Ministry of Natural Resources, Parks and Recreational Areas, Southwestern Region, London. OFER 8403. vii + 22 pp. + appendices.
  
  

St. Clair National Wildlife Area

© Natural Heritage Information Centre, 1998