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Oligotrophic Marsh

State Rank: S3     Global Rank: GNR   what are these ranks?


Detailed Community Description from Ecological Landscapes of Wisconsin

General natural community overview

Counties shaded blue have documented occurrences for Oligotrophic Marsh in the Wisconsin Natural Heritage Inventory database.

This herbaceous community of aquatic macrophytes is closed related to the submergent marsh community. It represents a distinctive assemblage of highly specialized submersed, rosette-forming aquatic macrophytes that occur in northern Wisconsin in clear, deep, circumneutral lakes with extremely soft water. Bottom materials are usually sand, or occasionally gravel, and there is often an abrupt transition from submergent marsh to a forested upland shore. The aquatic plants grow at depths that range from the shallows at the beach line, to several meters. Characteristic species include American shoreweed (Littorella uniflora), seven-angled pipe-wort (Eriocaulon aquaticum), yellow hedge-hyssop (Gratiola aurea), aquatic lobelia (Lobelia dortmanna), dwarf water-milfoil (Myriophyllum tenellum), brown-fruited rush (Juncus pelocarpus), and quillworts (Isoetes spp.).

Defining Characteristics and Similar Communities

Oligotrophic marshes are characterized by extremely soft water and occur in seepage lakes in northern Wisconsin, often with a bottom composed of sand and gravel. They are similar to submergent marshes but are dominated by rosette-forming aquatic macrophytes (see characteristic species above) rather than by dense beds of robust aquatic macrophytes such as pondweeds (Potamogeton spp.), waterweed (Elodea spp.), coontail (Ceratophyllum spp.), slender naiad (Najas flexilis), eel-grass (Vallisneria americana), water-milfoil (Myriophyllum spp.) and bladderwort (Utricularia spp.). Furthermore, where submergent marshes occur statewide in a variety of aquatic environments, oligotrophic marshes are restricted to clear, deep, circumneutral lakes in northern Wisconsin with extremely soft water.

Rare animals

Species of Greatest Conservation Need

Wisconsin Wildlife Action Plan graphic

The following Species of Greatest Conservation Need are listed according to their level of association with the Oligotrophic Marsh natural community type, based on the findings in Wisconsin's 2015 Wildlife Action Plan.

Scores: 3 = high association, 2 = moderate association, and 1 = low association. See the key to association scores for complete definitions.

Pickerel FrogLithobates palustris3
Mink FrogLithobates septentrionalis2

A Predaceous Diving BeetleAgabus aeruginosus2

Common GoldeneyeBucephala clangula1

Dragonflies and damselfliesScore
Sphagnum SpriteNehalennia gracilis3
Mottled DarnerAeshna clepsydra2
Spangled SkimmerLibellula cyanea1

Big Brown BatEptesicus fuscus2
Little Brown BatMyotis lucifugus2
Northern Long-eared BatMyotis septentrionalis2
Silver-haired BatLasionycteris noctivagans2

Blanding's TurtleEmydoidea blandingii3

Please see Section 2. Approach and Methods of the Wildlife Action Plan to learn how this information was developed.


The following Ecological Landscapes have the best opportunities to manage for Oligotrophic Marsh, based on the Ecological Landscapes of Wisconsin Handbook.

Map of the Ecological Landscapes of Wisconsin.

Ecological LandscapeOpportunity
Northern HighlandMajor
Northwest SandsPresent

Major (3 on map)
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.

Important (2 on map)
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.

Present (1 on map)
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.


Wisconsin Wildlife Action Plan graphic

What are conservation actions?

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for natural communities


The following are additional considerations for Oligotrophic Marsh in Ecological Landscapes with opportunities for protection, restoration, and/or management. For more information, see the Wildlife Action Plan.

Northern Highland

This Ecological Landscape contains numerous lakes that have the appropriate water chemistry, bottom types, and shoreline characteristics to support the oligotrophic marsh type. Composition consists of unusual assemblages of macrophytes, which exist as dense carpets of sterile rosettes on the lake bottom. Lakes of this type are poorly buffered by carbonate materials and are highly vulnerable to negative impacts such as acidification from air pollution. Development pressures are very high in this Ecological Landscape and there is a need to protect undeveloped shorelines in the near future.


Oligotrophic Marsh Photos

Oligotrophic Marsh Photo

Photo by Paul Skawinski.

Oligotrophic Marsh Photo

Photo by Paul Skawinski.

Oligotrophic Marsh Photo

Photo by Paul Skawinski.

Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.

Last revised: Tuesday, August 30, 2022