Shallow Marsh Annual

This tool lists various Habitat Fact Sheets developed by the Region 5 Regional Response Team. To suggest additions to this tool, please contact Barbi Lee. Click here for Inland Response Tactics Manual.

Shallow Marsh dominated by barnyard grass Echinocloa spp.
Rarely are shallow marshes dominated by a single species like this stand of barnyard or cockspur grass.

Image Credit: USGS
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Shallow marsh containing annual smartweeds Polygonum spp.
The hydrologic regime of shallow marsh annuals is typically seasonal inundation of up to six inches. With the exception of a disturbance, open water is not present.

Image Credit: USGS
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Shallow marsh overrun by cocklebur Xanthium spp.
Since shallow marsh annual habitats commonly occur in transition zones, they are vulnerable to colonization by invasive and noxious species, such as the cocklebur. Cocklebur seeds spread by sticking to fur and clothing.

Image Credit: USGS
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Nodding Bur-Marigold Bidens cernua
This native annual is an indicator species of shallow marsh annual habitats. It typically exhibits a sporadic occurrence but can grow in dense colonies on disturbed or open areas.

Image Credit: K. Chayka, MinnesotaWildflowers.info
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Nodding Bur-Marigold Bidens cernua Flower
The flower is typically 1-2 inches in diameter with 8 oval yellow petals. The blooming period occurs during August-early October.

Image Credit: K. Chayka, MinnesotaWildflowers.info
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Nodding Bur-Marigold Bidens cernua Leaves and Stem
Leaves are approximately 6 inches long and up to 1 inch wide, finely-toothed, and opposite attached. Stems may have red or purplish hue. Plant height ranges from 6-36 inches.

Image Credit: Peter M. Dziuk, MinnesotaWildflowers.info
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Devil's Beggartick Bidens Frondosa
This annual herb is common in shallow marsh annual habitats. It is one of the most widespread and common of the Biden spp. Single plants can have 1-3 flowering heads, characterized by a petal-less orange disk surrounded by long and hairy outer bracts.

Image Credit: Peter M. Dziuk, MinnesotaWildflowers.info
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Devil's Beggartick Bidens Frondosa Flower Head
The outer bracts surrounding the flower are thin and of varying lengths. The plant's flowering season ranges from July-October.

Image Credit: K. Chayka, MinnesotaWildflowers.info
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Devil's Beggartick Bidens Frondosa Leaves and Stem
The leaves are pinnate, occurring in groups of 3-5. They are arrow-shaped with narrow tips, wide bases and have serrated edges with a hairy underside. The stem is square, smooth, and branched. Plant height ranges from 1-3 feet.

Image Credit: K. Chayka, MinnesotaWildflowers.info
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Redroot Flatsedge Cyperus erythrorhizos
This annual plant, known for its red roots, can be found throughout North America in shallow marshes, ditches, and river banks. It can grow to be a meter tall, but is typically shorter.

Image Credit: Larry Allain, Courtesy of the USGS National Wetlands Research Center
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Stand of Redroot Flatsedge Cyperus erythrorhizos
This annual plant can be found on mudflats, riverbanks, and in shallow marshes.

Image Credit: Max Licher, Consortium of Intermountain Herbaria Image Modified by Matt Jacobson, UMRBA
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I. Habitat Description

The shallow marsh annuals habitat includes portions of lakes, ponds, backwaters, mudflats, or shorelines that are seasonally flooded and more than 10% vegetated with annual (non-persistent) emergent vegetation. Common vegetation types include wild millet (Echinochloa), smartweed/pinkweed (Polygonum), spike-rush (Eleocharis), nutsedge/red-root flatsedge (Cyperus), and beggarticks (Bidens). This habitat may have incursions of submersed, nonrooted-floating aquatics, or persistent emergent vegetation. It is typically found in areas which are seasonally flooded and have soils that are saturated or inundated by water up to 0.2 meters deep. During normal water conditions, there is little flow, though there can be wind-generated currents and stronger flows at inlets and outlets. During flood conditions, these habitats can be connected to rivers or streams, with strong currents and possibly large amounts of debris.

II. Sensitivity to Oil Spills

The shallow marsh annuals habitat is highly sensitive to oil spills. This biologically diverse habitat is critical to many plants and animals. Many animal species, especially waterfowl, rely on annual plants as a food source. Significant loss of this habitat would greatly affect the populations of these animals and consequently, the local ecology. Light refined oils with high amounts of water-soluble fractions can cause acute mortality to animals and plants in these shallow habitats. Heavier oils tend to coat vegetation and animals, though the vegetation may survive if oil coats only the stem. Plant mortality is heightened during the growing season.

III. Sensitivity to Response Methods

The following text describes potential adverse impacts to this habitat resulting from various oil spill response methods and provides recommendations to reduce impact when these methods are implemented. This is not intended to preclude the use of any particular methods, but rather to aid responders in balancing the need to remove oil with the possible adverse effects of removal. More detail about the response methods themselves can be found in the Inland Response Tactics Manual.

Additional Information

Download PDF

Shallow Marsh Annuals Additional Information

General Classification Handbook for Floodplain Vegetation in Large River Systems

Inland Oil Spills: Options for Minimizing Environmental Impacts for Freshwater Spill Response

National Wetlands Inventory

The U.S. National Vegetation Classification

Wetland Plants and Plant Communities of MN & WI, 3rd Edition

Oil Spills in Marshes: Planning and Response Considerations

MN Wildflowers Info

Least Adverse Habitat Impacts
Some Adverse Habitat Impacts
Most Adverse Habitat Impacts

Low-Pressure, Ambient-Water Flushing (see Inland Response Tactics Manual, pg. 15)

Maintain low output pressures (less than 50 psi) to avoid disrupting the substrate and vegetation.
Effectiveness increases with lighter oils because less residual oil is left in the environment.
This tactic can be used with flooding to prevent re-deposition of oil.
Use for spot removal of oil because of the limited area of effectiveness.

Flooding (see Inland Response Tactics Manual, pg. 15)

This tactic is only applicable in areas where the water level can be controlled, such as near locks and dams or in a small pond/marsh. Contact the U.S. Army Corps of Engineers water control regarding lock and dam operation.
Can be used selectively to remove localized heavy oiling This tactic is useful to remove oil trapped in vegetation, which can otherwise be difficult to herd toward recovery devices in open water. However, some oil may remain stranded in vegetation and will need to be removed through other means.

Exclusion or Deflection Booming (see Inland Response Tactics Manual, pg. 4)

Boom can be used to exclude or deflect the spill away from sensitive resources.
Effectiveness is increased by positioning boom at appropriate angles for the current speed.

Sorbents/Sorbent Boom (see Inland Response Tactics Manual, pg. 22)

In areas with vegetation at or above water, sorbents are most effective in water surrounding vegetation (as opposed to within/on top of vegetated areas).
Care is necessary during placement and recovery to minimize disturbance of vegetation. Work in boats to avoid driving oil into the sediment.
Pom-pom type sorbents are best for heavy viscous oils that coat the strands; sorbent boom is best for light, low-viscosity oils that can penetrate into the sorbents.
Absorbent boom must be changed frequently to prevent it from becoming a source of sheen.

In-Situ Burning (see Inland Response Tactics Manual, pg. 27)

Presence of a water layer on marsh surface can protect roots.
“Heavy ends” of petroleum product remain unburned and must be recovered. This residue will sink once it is cool.
The amount and placement of natural fuel in the surrounding area may present challenges to constraining the fire only to oiled areas.
Authorization of in-situ burning is subject to RRT approval, consultation and concurrence from the state and the Department of the Interior.
May be one of the least physically damaging means of moderate and heavy oil removal as it leaves plant roots intact.
May be difficult to protect riparian vegetation.

Debris/Vegetation Removal (see Inland Response Tactics Manual, pg. 26)

Most appropriate for oils that form a persistent, thick, sticky coating on the vegetation, such as medium and heavy oils.
Removal will release trapped oil and speed natural flushing rates.
Debris may be associated with nests or living areas (e.g., beaver and muskrat lodges), therefore impacts on resident animal habitat need to be considered.
If oil is trapped in floating vegetation, removal may be the only way to recover the oil in the absence of water currents.
May be appropriate to prevent secondary oiling of wildlife.
Damage by cleanup crews may be reduced by avoiding excessive cutting/removal.
Response crews entering the marsh can inadvertently trample vegetation during cleanup/removal. To reduce this impact: control and minimize access routes through the marsh; have personnel stand or kneel on boards while working; and conduct operations from boats when possible.