915 Sydney Bight
Geology and Seabed Morphology
This Unit extends from the eastern extension of Cape Breton Island, in the vicinity of Scatarie Island, to Cape North on the northern tip of the island. It is underlain mainly by Carboniferous rocks of the Maritime plain, a continuation of onshore geological formations and part of the Carboniferous-Triassic lowlands. Rocks of the Sydney Basin (which contain the onshore coal formations in the Sydney area) extend northward to Newfoundland, where they emerge in Georges Bay. Nearshore rocks in the northern portions are igneous where the Cape Breton highlands extend under the sea. The relatively flat bottom which slopes only gradually offshore in Sydney Bight forms St. Anns Bank, the only major bank in the Inner Shelf zone.
Sediments at depths of less than 100 m are sand and gravel mixtures, frequently in a thin layer through which bedrock is exposed. Deeper parts fall in the Middle Shelf (Unit 923) and are chiefly sands containing silt and clay (Sambro Sand). Nearshore deposits are formed of material eroded from coastal bedrock, and local hydrographic conditions can lead to the development of deposits of sand, gravel, clay, and other materials in some cases.
Especially in summer this area is influenced by the warmer, fresher waters that flow from the Gulf of St. Lawrence. In winter and spring the area is exposed to sea ice which moves out of the Gulf of St. Lawrence.
Many common seaweed species of the Atlantic coast are represented at shallow depths, including the kelps Laminaria longicruris, L. digitata, Sacchorhiza dermatodea, and Agarum cribrosum, the rockweed Fucus spp. and Irish Moss (Chondrus crispus). The latter two occur more frequently and kelps occur less frequently on Sydney Bight coasts than Atlantic coastal areas (Unit 911). The coast from Mira Bay to Great Bras d'Or Channel is sandstone, which is less suitable for attachment of seaweeds.
Atlantic Cod form dense wintering concentrations in deep water in the area and move into the southern Gulf of St. Lawrence in spring to spawn.
Concentrations of Snow Crab occur on soft bottoms on the Middle Shelf (Unit 923) surrounding Sydney Bight. Populations extend at suitable depths to the west of Cape Breton Island into the Northumberland Strait (Unit 914). Colonial seabirds such as puffins occur on the northern reaches of Cape Breton Island. The offshore waters have seabirds in summer which include puffins, shearwaters, and kittiwakes, and winter distributions of fulmars, kittiwakes, and murres.
In addition to fishing, considerable industrial and transportational use is made of the waters of Sydney Bight. Fisheries include lobster, Snow Crab, and ground fisheries, and Capelin have recently been coming to the shores to spawn in early summer, providing a small recreational fishery. Industrial plants, electricity-generating stations, and urbanization have created several forms of pollution in the coastal water. Some fine beaches (e.g., Dominion), the scenic east side of the Cape Breton highlands, and wildlife (e.g., Bird Islands) are important tourist attractions. There is heavy marine traffic, including the Newfoundland ferries and vessels en route to and from the St. Lawrence River.
Sites of Special Interest
- Bird Islands (IBP Proposed Ecological Site 24) - bird nesting sight, with rare arctic-alpine plantsPoint Aconi and area
|T3.5 Offshore Bottom Characteristics|
|T6.1 Ocean Currents|
|T6.2 Oceanic Environments|
|T11.7 Seabirds and Birds of
|T11.12 Marine Mammals|
|T11.14 Marine Fishes|
|T12.11 Animals and Resources||
|Associated Coastal Districts and Units|
|210 Plateau-Fir Forest|
|220 Steep Slopes|
|552 Victoria Coastal Plain|
|531 Sydney Coalfield|