Coastal Plain Marsh
Coastal plain marsh is a grass-, spike-rush-, and rush-dominated wetland community that contains numerous plant disjuncts from the Atlantic and Gulf coastal plains. The community occurs in depressions on sand deposits associated with postglacial lakes and outwash channels in western Lower Michigan, northern Indiana, northern and central Wisconsin, and the southeastern Georgian Bay region of Ontario.
County Distribution Map
Global Rank: G2 - Imperiled
State Rank: S2 - Imperiled
Coastal plain marshes occur in depressions in sandy, acidic, pitted outwash plains and lakeplains. They are often found along the shores of softwater seepage lakes, ponds, and depressions, where water levels fluctuate both seasonally and yearly. Coastal plain marsh may be bordered by other wetland communities such as a floating bog, lakeplain prairie, wet-mesic sand prairie, shrub-carr, or southern hardwood swamp. Today, most coastal plain marshes are bordered by closed-canopy dry southern forest, dry-mesic southern forest, and dry-mesic northern forest. However, in the 1800s, prior to fire suppression, the uplands bordering coastal plain marshes supported a variety of open-canopy, fire-dependent communities including oak openings, lakeplain oak openings, bur oak plains, oak barrens, oak-pine barrens, dry sand prairie, mesic sand prairie, and dry-mesic prairie.
The sandy soils underlying coastal plain marshes are strongly to very strongly acidic and nutrient-poor. Organic deposits of peat or sandy peat may overlay the sandy substrate, and in some basins a clay layer may occur several meters below the surface.
The dominant natural processes in coastal plain marshes are seasonal and yearly water level fluctuations. Seasonally, water levels tend to be highest during the winter and spring and lowest in late summer and early autumn. Yearly water level fluctuations are less predictable. Fluctuating water levels facilitate seed germination by drawing down water levels and thus allowing direct sunlight to penetrate the exposed pond shore and trigger seed germination. Fluctuating water levels also limit competition from woody plants and are an important mechanism for seed and nutrient dispersal to the outer margins of the wetland basin.
Historically, during low-water years, fire likely carried from adjacent uplands into coastal plain marshes. Because fire has been shown to increase seed germination, enhance seedling establishment, and bolster flowering, it likely acted as an important mechanism for maintaining plant species diversity and replenishing seed banks.
Long distance seed dispersal among Midwest coastal plain marshes and between the Midwest and Atlantic and Gulf coastal plains is thought to be facilitated by migratory waterfowl. Waterfowl moving among nearby wetlands may also restore species that have been depleted from a site’s seed bank.
Coastal plain marshes typically contain four distinct vegetation zones, often occurring as concentric bands around the open water portions of depressions, lakes, and ponds. The deepest portion of the depression is usually inundated and supports floating aquatic plants such as water shield (Brasenia schreberi), sweet-scented water-lily (Nymphaea odorata), pondweeds (Potamogeton spp.), and bladderworts (Utricularia spp.). Along the shoreline is a seasonally flooded zone that supports a sparse graminoid cover of species such as tall beak-rush (Rhyncospora macrostachya, state special concern) and autumn sedge (Fimbristylis autumnalis). In the saturated soils further from shore is a dense graminoid-dominated zone of bluejoint grass (Calamagrostis canadensis), twig-rush (Cladium mariscoides), coastal flat-topped goldenrod (Euthamia caroliniana), beak-rush (Rhynchospora capitellata), and others. Lastly, many coastal plain marshes contain a temporarily flooded shrub and tree zone with black chokeberry (Aronia prunifolia), buttonbush (Cephalanthus occidentalis), dogwoods (Cornus spp.), and steeplebush (Spiraea tomentosa). In addition to the above, the following species are characteristic of coastal plain marsh: three-awned grass (Aristida necopina), bushy aster (Symphyotrichum dumosum), sedge (Bulbostylis capillaris), umbrella sedge (Cyperus bipartitus), Robin’s spike-rush (Eleocharis robbinsii), pipewort (Eriocaulon aquaticum), dwarf bulrush (Lipocarpha micrantha, state special concern), Canadian St. John’s-wort (Hypericum canadense), two-flowered rush (Juncus biflorus), brown-fruited rush (J. pelocarpus), round-headed rush (J. scirpoides, state threatened), bog clubmoss (Lycopodiella inundata), panic grass (Dichanthelium spretum), beak-rush (Rhynchospora capitellata), tooth-cup (Rotala ramosior), tall nutrush (Scleria triglomerata, state special concern), bulrushes (Schoenoplectus purshianus and S. smithii), little ladies’-tresses (Spiranthes tuberosa), Virginia marsh St. John’s-wort (Triadenum virginicum), lance-leaved violet (Viola lanceolata), and yellow-eyed-grass (Xyris torta).
Seasonally inundated coastal plain marshes provide breeding habitat for amphibians and are important feeding areas for shorebirds and waterfowl.
- Bartonia paniculata (panicled screw-stem, state threatened)
- Carex albolutescens (greenish-white sedge, state threatened)
- Carex festucacea (fescue sedge, state special concern)
- Echinodorus tenellus (dwarf burhead, state endangered)
- Eleocharis atropurpurea (purple spike-rush, state special concern)
- Eleocharis engelmannii (Engelmann’s spike-rush, state special concern)
- Eleocharis melanocarpa (black-fruited spike-rush, state special concern)
- Eleocharis microcarpa (small-fruited spike-rush, state endangered)
- Eleocharis tricostata (three-ribbed spike-rush, state threatened)
- Fuirena squarrosa (umbrella grass, state threatened)
- Gratiola virginiana (round-fruited hedge hyssop, state threatened)
- Hemicarpha micrantha (dwarf bulrush, state special concern)
- Isoetes engelmannii (Engelmann’s quillwort, state endangered)
- Juncus brachycarpus (short-fruited rush, state threatened)
- Juncus scirpoides (round-headed rush, state threatened)
- Lechea minor (least pinweed, state special concern)
- Lechea pulchella (Leggett’s pinweed, state threatened)
- Ludwigia alternifolia (seedbox, state special concern)
- Ludwigia sphaerocarpa (globe-fruited seedbox, state threatened)
- Lycopodiella margueriteae (northern prostrate club moss, state threatened)
- Lycopodiella subappressa (appressed bog club moss, state special concern)
- Panicum longifolium (long-leaved panic grass, state threatened)
- Panicum verrucosum (warty panic grass, state threatened)
- Polygala cruciata (cross-leaved milkwort, state special concern)
- Polygonum careyi (Carey’s smartweed, state threatened)
- Potamogeton bicupulatus (waterthread pondweed, state threatened)
- Proserpinaca pectinata (mermaid-weed, state endangered)
- Psilocarya scirpoides (bald-rush, state threatened)
- Pycnanthemum verticillatum (whorled mountain mint, state special concern)
- Rhexia mariana var. mariana (Maryland meadow beauty, state threatened)
- Rhexia virginica (meadow beauty, state special concern)
- Rhynchospora macrostachya (beak-rush, state special concern)
- Rhynchospora recognita (globe beak-rush, state endangered)
- Rotala ramosior (tooth-cup, state special concern)
- Sabatia angularis (rose pink, state threatened)
- Scirpus hallii (Hall’s bulrush, state threatened)
- Scirpus torreyi (Torrey’s bulrush, state special concern)
- Scleria pauciflora (few-flowered nut-rush, state endangered)
- Scleria reticularis (netted nut-rush, state threatened)
- Scleria triglomerata (tall nut-rush, state special concern)
- Sisyrinchium atlanticum (Atlantic blue-eyed-grass, state threatened)
- Sisyrinchium strictum (blue-eyed-grass, state special concern)
- Utricularia inflata (floating bladderwort, state endangered)
- Acris crepitans blanchardi (Blanchard's cricket frog, state special concern)
- Botaurus lentiginosus (American bittern, state special concern)
- Chlidonias niger (black tern, state special concern)
- Circus cyaneus (northern harrier, state special concern)
- Cistothorus palustris (marsh wren, state special concern)
- Clemmys guttata (spotted turtle, state threatened)
- Cordulegaster erronea (tiger spiketail, state special concern)
- Cygnus buccinator (trumpeter swan, state threatened)
- Dorydiella kansana (leafhopper, state special concern)
- Emydoidea blandingii (Blanding’s turtle, state special concern)
- Gallinula chloropus (common moorhen, state special concern)
- Ixobrychus exilis (least bittern, state threatened)
- Meropleon ambifusca (Newman’s brocade, state special concern)
- Nycticorax nycticorax (black-crowned night heron, state special concern)
- Orphulella p. pelidna (green desert grasshopper, state special concern)
- Paroxya hoosieri (Hoosier locust, state special concern)
- Phalaropus tricolor (Wilson’s phalarope, state special concern)
- Rallus elegans (king rail, state endangered)
- Sistrurus c. catenatus (eastern massasauga, federal candidate species and state special concern)
- Tyto alba (barn owl, state endangered)
Biodiversity Management Considerations
Given that even small changes in hydroperiod can cause significant shifts in wetland community composition and structure, protection of the regional and local hydrologic regime is critical to the long-term preservation of coastal plain marshes. If water levels are stabilized, perennials and woody species may become established, displacing less competitive annuals and coastal plain specialists.
Coastal plain marshes occur as shallow depressions within a fire-dependent matrix of upland forest and barrens. Prescribed fire management of coastal plain marsh, which should include burning adjacent wetland and upland communities, can be used to stimulate seed germination and flowering, reduce encroachment of woody plants, and maintain a diverse seed bank.
Coastal plain marshes are threatened by off-road vehicles and fire suppression. Off-road vehicles can greatly disturb the seed bank, alter surface hydrology, and create open microsites that are easily colonized by non-native plants. Fire suppression facilitates shrub and tree establishment during low water years and allows for the build up of a thick layer of litter, which stifles seed germination and seedling establishment. As coastal plain marshes contain a unique suite of coastal plain disjuncts, the loss of any single marsh may negatively impact population dynamics at other sites by eliminating opportunities for genetic exchange and recolonization.
Monitoring and control efforts to detect and remove invasive species are critical to the long-term viability of coastal plain marsh. Particularly aggressive invasive species that may colonize the edges or interior of coastal plain margins and thereby threaten diversity and community structure include reed (Phragmites australis subsp. australis), reed canary grass (Phalaris arundinacea), narrow-leaved cat-tail (Typha angustifolia), hybrid cat-tail (Typha xglauca), purple loosestrife (Lythrum salicaria), glossy buckthorn (Frangula alnus), and multiflora rose (Rosa multiflora).
Community size, basin morphology, presence and depth of water, and plant species composition can all vary significantly among coastal plain marshes, even where they occur in close proximity to one another.
- Brodowicz, W.W. 1989. Report on the coastal plain flora of the Great Lakes region. Michigan Natural Features Inventory, Lansing, MI.
- Chapman, K.A. 1990. Community characterization abstract: Coastal plain marsh. Midwest Regional Office of The Nature Conservancy, Minneapolis, MN. 6 pp.
- Kost, M.A., and M.R. Penskar. 2002. Natural community abstract for coastal plain marsh. Michigan Natural Features Inventory, Lansing, MI. 5 pp.
- Reznicek, A.A. 1994. The disjunct coastal plain flora in the Great Lakes region. Biological Conservation 68: 203-215.
- Schneider, R. 1994. The role of hydrologic regime in maintaining rare plant communities of New York’s coastal plain pondshores. Biological Conservation 68: 253-260.
- van der Valk, A.G. 1986. The impact of litter and annual plants on recruitment from the seed bank of a lacustrine wetland. Aquatic Botany 24: 13-26.
- Wisheu, I.C., and P.A. Keddy. 1989. The conservation and management of a threatened coastal plain plant community in eastern North America (Nova Scotia, Canada). Biological Conservation 48: 229-238.
For a full list of references used to create this description, please refer to the natural community abstract for coastal plain marsh.
Kost, M.A., D.A. Albert, J.G. Cohen, B.S. Slaughter, R.K. Schillo, C.R. Weber, and K.A. Chapman. 2007. Natural Communities of Michigan: Classification and Description. Michigan Natural Features Inventory, Report No. 2007-21, Lansing, MI.