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BC Conservation Data Centre: Ecological Community Summary

Distichlis spicata Estuarine Marsh
seashore saltgrass Estuarine Marsh

 
Scientific Name: Distichlis spicata Estuarine Marsh
English Name: seashore saltgrass Estuarine Marsh
Scientific Name - Concept Reference: MacKenzie, W.H. and J.R. Moran. 2004. Wetlands of British Columbia: a guide to identification. Res. Br., B.C. Min. For., Victoria, B.C. Land Manage. Handb. No. 52.
Ecosystem Group: Estuarine Realm: Estuarine Marsh Class (Em)
   
Conservation Status / Legal Designation
Global Status: GNR (Dec 2008)
Provincial Status: S1S2 (Feb 2018)
BC List: Red
Provincial FRPA list:   
Notable Species:
 
Ecology & Dynamics
Environmental Summary: This open, salt-marsh wetland is dominated by Distichlis spicata var. spicata (seashore saltgrass) and occurs in the intertidal zone of protected shorelines in south coastal B.C. It is most abundant in shallow lagoons or bays enclosed by spits or other protective features which create low-energy environments for sediment accretion (Pennings and Bertness 2001). It also occurs seaward of sedge-dominated estuarine marsh communities in some river deltas (MacKenzie and Moran 2004). All occurrences are in the higher intertidal zone from about +1.0 to +1.8 m (geodetic datum). Most are submerged daily by tides, but some are flooded less frequently.

Soils are composed of layers of silty-sand or clay with a high proportion (>10%) of organic material derived from marine algae and eelgrass. For example, soil analysis in lagoon sediment in Boundary Bay found it was composed of approximately 60% silt, 32% clay, and 15% organic matter (Page et al. 1998).

MacKenzie and Moran (2004) described a Seashore Saltgrass estuarine association on fine textured, poorly drained sediments that are flooded for prolonged periods by brackish water. This ecological community is characterized as salt marsh rather than estuarine marsh due to its occurrence in locations that have purely saline waters without any freshwater inputs (Pennings and Bertness 2001; MacDonald and Barbour 1974).

Prominent sites in the Strait of Georgia with Seashore Saltgrass Herbaceous Vegetation include the shore of Boundary Bay, the Tsawout wetland near Sidney Spit, Witty's Lagoon near Metchosin, and Sidney Lagoon on Sidney Island (within the Southern Gulf Islands National Park Reserve). Smaller occurrences can also be found in Port Moody, Roberts Bank and in the Burrard Inlet (Page 2011a; Page 2011b). Many very small occurrences are located along the coastline of east Vancouver Island and the Sunshine Coast from Malaspina Peninsula to Howe Sound (Sensitive Ecosystems Inventories; 2004, 2005). Ward et al. (1992) found that salt marsh (including seashore saltgrass communities) accounted for only 4% (235 ha) of the marshes in the Lower Fraser River and just over 8% of the marshes in the Fraser River estuary.
Vegetation Summary: This ecological community is an open, salt marsh wetland community found along B.C.'s south coast. The majority of occurrences are located in protected shoreline areas of the Strait of Georgia. It is characterized by low plant species richness and low (<30 cm tall), often monotypic growth of Distichlis spicata var. spicata (seashore saltgrass). This grass species is perennial, retaining some leaf and stem structure in the fall but senescing over the winter. It is often clonal (Hitchcock 1971), forming extensive rhizomes that allow it to spread rapidly into disturbed or newly deposited soil. It can also disperse by seed.

Distichlis spicata var. spicata is generally very abundant (> 90% cover) in this community with few other plant species tolerant of the harsh environmental conditions of high salinity and frequent tidal inundation. Occasional associate species are Sarcocornia pacifica (American glasswort), Potentilla anserina (common silverweed), Atriplex patula (common orache), Symphyotrichum subspicatum (Douglas' aster), Glaux maritima (sea-milkwort), and Spergularia canadensis (Canadian sand-spurry) (MacKenzie and Moran 2004; Stacey and Filatow 2009; Page 2011a; Page 2011b). Bolboschoenus maritimus (seacoast bulrush) sometimes occurs in brackish ponds within a matrix of Distichlis spicata var. spicata Herbaceous Vegetation. Composition varies by elevation and salinity but there is little regional variation in structure or composition. Transition to adjacent communities such as Sarcocornia pacifica salt marsh is often controlled by elevation in relation to tidal inundation.

This community is often associated with the estuarine marsh Sarcocornia pacifica - Glaux maritima (American glasswort - sea-milkwort), estuarine sedge or rush marshes, and unvegetated or algae-rich mudflats (MacKenzie and Moran 2004).
Dynamic Processes Summary: This salt marsh ecosystem occurs in a highly stressful environment characterized by regular flooding by saline marine water, disturbance from waves, and competition for limited resources (Pennings and Bertness 2001). An important process sustaining this ecological community is the slow accumulation of inorganic and organic sediment. The community is confined to low-energy sites which act as a net sink for marine sediment. Sediment accretion rates in these communities are around 3.6 mm/year in salt marshes in Oregon and Washington (Thom 1992) which may be similar to rates on B.C.'s south coast. Succession to higher marsh communities such as Deschampsia- or Agrostis-dominated marshes (see MacKenzie and Moran 2004) can occur over time with the increased sediment accumulation. Changes to sediment movement from diking or the construction of wharves and breakwaters may reduce or increase sediment movement and deposition in salt marshes, which in turn can change their extent, structure and/or composition.

Herbivore browsing (e.g. by geese), which can be significant in other coastal marshes, is minimal in seashore saltgrass communities.

The increase in sea level predicted with climate change would affect the distribution and extent of this community. It is possible that as the intertidal zone moves up in elevation, Seashore Saltgrass Herbaceous Vegetation occurrences will also move up to occupy the same ecological niche they currently do, if suitable area is available. However, this would be dependent upon a number of factors including the rate of sea level rise and the nature of the ecosystems previously occupying the newly inundated zone.
Spatial Pattern: Small patch
 
Distribution
Endemic:
   
Authors / Contributors
Author: Schaefer, C. and C.M. Cadrin
Last updated: Apr 20, 2012
   
References and Related Literature
Flynn, S., C. Cadrin, and D. Filatow. 2006a. Estuaries in British Columbia. B.C. Minist. Environ., Ecosystems Branch. Victoria, B.C. 6pp.
MacDonald, K.B. and M.G. Barbour. 1974. Beach and salt marsh vegetation of the North American Pacific Coast. Pages 175-233 in R.J. Reimold and W.H. Queen, ed. Ecology of Halophytes. Academic Press Inc. New York. 58pp.
MacKenzie, W.H. and J.R. Moran. 2004. Wetlands of British Columbia: a guide to identification. Res. Br., B.C. Min. For., Victoria, B.C. Land Manage. Handb. No. 52.
McPhee, M., P. Ward, J. Kirkby, L. Wolfe, N. Page, K. Dunster, N.K. Dawe, and I. Nykwist. 2000. Sensitive Ecosystems Inventory: East Vancouver Island and Gulf Islands, 1993 - 1997. Volume 2: Conservation Manual. Tech. Rep. Ser. No. 345, Can. Wildl. Serv., Pac. and Yukon Reg., BC.
Page, N. 2011b. Grauer Marsh Vegetation Assessment. Unpublished memo prepared by Raincoast Applied Ecology for Ducks Unlimited Canada. 21 pp.
Page, N., J. Millar, J. Harper, R. Gillie, A. Poynter, I. Robertson, and M. Tarbotton. 1998. Beach Grove Lagoon: shoreline processes and habitat assessment study. Unpublished report for GVRD Parks and others. 58 pp. + appendices.
Page, N.A. 2010. Cordova Shore conservation strategy. Unpublished report prepared for Capital Regional District Regional Parks, Tsawout First Nation, and Canadian Wildlife Service, by Raincoast Applied Ecology, Vancouver, BC. 66 pp.
Page, Nick. Personal communication. Ecologist, Raincoast Applied Ecology.
Pennings, S.C. and M. D. Bertness. 2001. Salt Marsh Communities. In: Marine Community Ecology. M. D. Bertness, S.D. Gaines, and M. Hay (Editors). Sinauer Associates, Sunderland Massachusetts.
Sensitive Ecosystems Inventory [SEI] of East Vancouver Island and Gulf Islands: Sensitive Ecosystems Mapping, Disturbance Mapping and Re-evaluation of Major Riparian Corridors. 2004. Prepared by Axys Environ. Consulting Ltd. for Environ. Can., Can. Wildl. Serv., B.C. Minist. Sustainable Resour. Manage., and B.C. Minist. Water, Land and Air Prot., and the Habitat Conserv. Trust Fund. 66 mapsheets, 1:20 000 scale.
Sensitive Ecosystems Inventory [SEI] of the Sunshine Coast and Adjacent Islands. 2005. Cadrin, C., C. Erwin, B. Fuller, C. Schaefer and J. Stacey. 1:20 000 spatial data.
Terrestrial Ecosystem Mapping [TEM] of the Coastal Douglas-fir Biogeoclimatic Zone. 2008. Prepared for B. Zinovich, Integrated Land Management Bureau, B.C. Minist. of Agric. and Lands, Nanaimo B.C. by Madrone Environmental Services, Duncan B.C. 1:20,000 spatial data.
Terrestrial Ecosystem Mapping [TEM] of TIXEN/Cordova Spit. 2009. Prepared for the Tsawout First Nation, CRD Parks, Canadian Wildlife Service and Central Saanich Parks, by J. Stacey and D. Filatow, B.C. Minist. of Environ. Victoria BC. 1:20,000 spatial data.
Thom, R.M. 1992. Accretion rates of low intertidal salt marshes in the Pacific Northwest. Wetlands 12 (3): 147-156.
Ward, P., G. Radcliffe, J. Kirkby, J. Illingworth, and C. Cadrin. 1998. Sensitive Ecosystems Inventory: East Vancouver Island and Gulf Islands 1993-1997. Volume 1: Methodology, Ecological Descriptions and Results. Tech. Rep. Ser. No. 320, Can. Wildl. Serv., Pac. and Yukon Reg., BC.
Ward, P., K.Moore and R.Kistritz. 1992. Wetlands of the Fraser Lowland, 1989: an inventory. Technical Report Series No. 146, Canadian Wildlife Service, Pacific and Yukon Region, B.C. 216pp.
 

Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.

Suggested Citation:

B.C. Conservation Data Centre. 2012. Ecological Community Summary: Distichlis spicata Estuarine Marsh. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 15, 2026).