Wetlands of Non-Calcareous Lakes in

East Central Minnesota

Series Description

The water chemistry of Minnesota lakes reflects, to a great extent, the parent material (geologic substrate) of the locale, influenced by climate patterns (e.g., precipitation vs. evaporation) Gorham et al. (1983). A gradient of hardness, or amount of calcium carbonate, varies considerably across the aquatic systems of the state and greatly affects the biota that is typical of a lake (especially plants and invertebrates). This series considers wetlands associated with those lakes that are low in calcium carbonate and occur in the east-central portion of the state. These littoral wetlands are found along the borders of lakes, often in sheltered areas such as bays. They occupy the portion of the lake from the shore outward to a depth where rooted plants can no longer grow.

As lakes are abundant in Minnesota, these are some of the most familiar types of wetlands to many people. These wetlands originally developed on lake edges after the glaciers receded from this area. Littoral wetlands support a rich array of Minnesota's biodiversity. Many plants make their home in this band of habitat around our lakes. Some of the more familiar inhabitants include Eleocharis spp. (spikerushes), Scirpus spp. (bulrushes), Sagittaria latifolia (arrowhead), Nymphaea odorata (white water lily), Potamogeton spp.. (pondweeds), and Ceratophyllum demersum (coontail). Invertebrates such as snails, Coleoptera (beetles), Odonata (dragonflies), and Ephemeroptera (mayflies) also inhabit these areas as do several species of reptiles and amphibians. Many species of birds also utilize lakeshore wetlands for breeding and foraging, making the sight of ducks, Gavia immer (common loon), Ardea herodias (great blue heron) or Ceryle alcyon (belted kingfisher) a common one in these wetland habitats. Fish, of course, are also found in the lakes of Minnesota. Common species found in the littoral zone include: Perca flavescens (yellow perch) and Lepomis cyanellus (green sunfish). Many fish, in fact, spawn in these lakeshore wetland areas in the spring or summer, making these areas critical to many species.

Land use in the watersheds of these lakes varies greatly. The northern lakes are located in a region dominated by mixed coniferous/deciduous forest and wetlands, and the southern sites lie in an area dominated by deciduous forest and agricultural land. One study site, Silver Lake, is located within an urban setting. Lakes in Minnesota also differ in their recreational usage. Some lakes are used by countless recreationists each year for activities such as swimming, boating, and fishing. Many of Minnesota’s lakes have been subjected to heavy shoreline development. Such development is often accompanied by removal of upland and littoral vegetation, resulting in reduced wildlife habitat and increased shoreline erosion.

During the 1995 field season, over 30 sites were assessed for inclusion in this series. People and agencies who helped us identify potential research sites include Kelly Smith (Carlton County Soil and Water Conservation District (SWCD)), Norm Aaseng (Minnesota Department of Natural Resources- Ecological Services), Tom Remus (Savanna Portage State Park), and many other MNDNR and county SWCD personnel. Sites rejected from the series included those located in lakes smaller than 50 acres or larger than 1500 acres, sites in very shallow lakes, sites that lack (and historically lacked) a littoral wetland zone characterized by emergent vegetation, sites with littoral vegetation exclusively growing on a floating mat, sites that are considerably difficult to access, and sites located in central or western Minnesota where lake water is typically calcareous. The fifteen research sites chosen represent a gradient of human disturbance at the local, regional, and watershed scale. Examples of local disturbance to the sites include shoreline development, rip-rapping of the shoreline, upland vegetation removal, littoral wetland vegetation removal, artificial beaches, and recreational boating. Regional and watershed scale disturbance is characterized by land use activities such as row crop agriculture and urban development. Sites at Remote Lake (RE), Wolf Lake (WO), Grace's Lake (GL), and Hay Lake-Aitkin (HA) are considered to be least impacted. Moderate impacts from shoreline and watershed development are evident at Round Lake (RO), Park Lake (PA), Hay Lake-Carleton (HC), Rush Lake (RU), and Fish Lake-Anoka (FA). Silver Lake (SI), Moosehead Lake (MO), Chub Lake (CH), Big Lake (BI), Eagle Lake (EA), and Fish Lake-Pine (FP) are most impacted by human uses including intensive shoreline development, heavy recreational boat traffic, and significant urban and agricultural land use in the watersheds.

The portion of the lake sampled for the study was chosen so that it represented the typical land use condition of the lake. Sites were located in areas that were currently or historically littoral wetlands (rather than beach or steep slope).

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