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Marsh/Fine Sediment Shoreline

Mortimer Spit - South Side Facing Shark Cove, South Pender Island

Mortimer Spit, South Pender Island
Marshfinesediment Fine Sediment .2.Mortimer Spit South Pender Island


Marsh/fine sediment shorelines are relatively rare, highly valued habitats in the Gulf Islands, accounting for a small percentage of the total shoreline. Marshes are found in areas of low wave energy where there is freshwater input from streams and drainage channels. Fringing salt marsh and sometimes larger areas of estuary vegetation can be present.  An example of marsh/fine sediment shore type is on the south side of Mortimer Spit, South Pender Island. 

The marsh/ fine sediment shore type is less than 5% of the total shoreline in the Islands Trust area based on the twelve major islands that had shoreline mapping completed.  Salt Spring Island has the most at 7%, while Hornby Island has the least at 0%.   Less than 2% of South Pender Island's shoreline has been mapped as the pebble/ sand shore type.

Physical Features

The physical form of marsh/fine sediment shorelines is largely dependent upon the amount of freshwater inputs, sediment supply, tides, wind and longshore sediment transport. The fine sediments of marshes may trap pollutants and accumulate organic material leading to reduced (hypoxic) oxygen or no oxygen (anoxic) conditions in and just above the sediments. Marsh/fine sediment shorelines may tend to accumulate sediment in times of freshwater runoff or calm spring and summer months and loose sediment during the fall and winter storm season. 

Biological Features

Marsh/fine sediment shorelines are characterized by salt tolerant plant communities that are specially adapted to live in the harsh conditions of the changing salinity, temperature and tidal inundations in the transition from marine to terrestrial environment.  Marsh are highly productivity and are important contributes to nutrients and food for many organisms in the coastal food webs. These important habitats support many species for at least a portion of their life cycle, including rearing areas for juvenile fish, and feeding areas for many birds such as Great Blue Herons, shorebirds and other waterfowl.  

Eelgrass meadows are commonly associated with estuary and salt marsh and also contribute to the concentration of productive and highly valued habitat in this shore type.FineMarshSedimentBCStewardship

Page last updated: 01/10/15
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