2.3.2 Biologic Integrity

Landscape

Large areas of undisturbed or minimally disturbed forest and wetland in the subwatershed have been designated Regionally Significant Ecological Areas by the DNR (see Figure 6), including nearly all of the Carver Park Reserve.   The Minnesota County Biological Survey (MCBS) identified several areas of moderate or high biodiversity significance both within and outside of the regional park, including a large area of maple-basswood forest and tamarack swamp surrounding and west of Stone, Steiger and Zumbra Lakes.

The Minnesota Natural Heritage Information System lists several rare natural features in this subwatershed.  These include bald eagle, a federally-listed threatened species; trumpeter swans, a state-listed threatened species; and cerulean warbler, a bird of state species special concern, and the least darter, a fish of state species of special concern. 

Lakes

There are eleven lakes in the Six Mile Marsh subwatershed in-line or connected by channels to Six Mile Creek, and numerous other water resources.   Many of the lakes support DNR-managed fisheries.  Steiger Lake in the Carver Park Reserve has had a catch and release requirement for northern pike and largemouth bass since 1988 in an attempt to foster a population of trophy-size fish.  Zumbra-Sunny has also been managed for largemouth bass.

While no comprehensive data is available on aquatic vegetation, several of the lakes - including Auburn, Parley, Piersons, Steiger, Stone, Wasserman, and Zumbra – have documented Eurasian watermilfoil infestations.  Auburn and Wasserman have excessive amounts of the plant, which on Auburn can impede navigation around the perimeter of the lake.  Zumbra has been treated for milfoil in 1993-94 and for curlyleaf pondweed in 2004.

Table 1.  DNR fish survey data.

Lake 

Survey Year

Fishery

Dominant Fish

Parley

2004

Sport - walleye

Black crappie, bluegill, black bullhead, yellow perch

Auburn (east & West)

2000

Panfish

Black bullhead, black crappie, northern pike, bluegill

Pierson

2001

Panfish

Black crappie, bluegill, largemouth bass, carp

Wasserman

1999

Panfish

Black bullhead, black crappie, bluegill, carp

Steiger

2003

Sport

Black crappie, bluegill, northern pike

Zumbra

2004

Sport

Bluegill, black bullhead, largemouth bass, northern pike

Stone

1996

Panfish

White crappie, black bullhead

Source: Minnesota DNR

Streams

Biological sampling on Six Mile Creek was conducted as a part of the Upper Watershed Stream Assessment.  Eight sites were sampled; only five yielded more than the 100 organisms typically needed to assure a statistically valid score.  The F-IBI – an Index of Biotic Integrity identified to the organism's family level – for most of the sites fell into the Fairly Poor category.  However, the F-IBI does not allow discrimination between low scores due to poor water quality or low scores due to lack of habitat.  Six Mile Creek showed the most diversity of the upper watershed streams, with thirteen aquatic invertebrate taxa representing thirteen families.  Most of the taxa found were those that are tolerant of poor water quality, although some taxa that are less tolerant were identified in some reaches.    Six Mile Creek is mainly a wetland stream, and lacks the habitat complexity necessary to sustain a varied macroinvertebrate community.  Additional sampling and identification of organisms to the species level would be necessary to adequately characterize the biological integrity of Six Mile Creek.

Wetlands

A high density of wetlands is present in the subwatershed.  A number of them were identified in the 2003 MCWD Functional Assessment of Wetlands (FAW) as having exceptional to high vegetative diversity and wildlife habitat potential as well as having high aesthetic values.   Tamarack swamp is present in the Carver Park Reserve.  Much of the riparian area along Six Mile Creek is wetland and contains mostly invasive or non-native vegetation, which includes cattails and some reed canary grasses.  There are small patches of forest and woodland as well as larger, more extensive grasslands in the upland areas of the Carver Park Reserve (see Figure 12).