Aquatic Vegetation of Wilkins Lake (DOW ) Aitkin County, Minnesota

Transcription

1 Aquatic Vegetation of Wilkins Lake (DOW ) Aitkin County, Minnesota July 27 and 28, 2005 Pepaed by: Kevin Mott Minnesota Depatment of Natual Resouces Aquatic Plant Management Pogam 1601 Minnesota Dive Bained, MN Phone:

2 Acknowledgements: Sampling and data enty: Kevin Mott and Ed Feile, Minnesota Depatment of Natual Resouces Division of Fish and Wildlife, Bained. Jeff Weite & Joe Backowski Minnesota Depatment of Natual Resouces Division of Ecological Sevices, Bained. Repot fomat: This epot follows the basic famewok of moe exhaustive suveys pefomed by Donna Pelebeg, Minnesota Depatment of Natual Resouces Division of Ecological Sevices, Bained. An example can be found at:

3 Intoduction Wilkins Lake (1-102) is located five miles south of the town of Palisade, in cental Aitkin County, Minnesota (Figue 1). It eaches a maximum depth of 39 feet and coves 372 aces, of which 28% is less then 15 feet deep. This shallow wate zone, temed the littoal zone, is the most poductive aea of the lake and suppots the geatest divesity of aquatic oganisms. Thee is a township owned public access in the southeast potion of the lake. The wate claity and quality of Wilkins Lake is good when compaed to othe lakes in the nothen lakes and foest egion of Minnesota (MPCA, 2006). Popula game fish species such as nothen pike, black cappie and bluegill sunfish have natually sustaining populations that povide a vaiety of angling oppotunities. Walleyes, which have limited natual epoduction due to lack of suitable habitat, have been stocked to povide an additional eceational oppotunity fo angles. Figue 1. Location of Wilkins Lake. Aitkin [ Vegetation Suvey Objectives: Thee suveys wee pefomed on Wilkins Lake and neighboing Whispeing Lake. The pupose of the fist suvey was to detemine if culy-leaf pondweed occued in eithe lake. Gowing concen ove the impacts of such exotic invasive species has esulted in an inceased awaeness of the impotance of a healthy native aquatic plant community. The pupose of the second suvey was to descibe the cuent status of the aquatic plant community in Wilkins Lake. Simple statistics such as maximum depth of plant gowth and fequency of common plants by depth can be calculated fom this suvey. This infomation can then be used to help develop, implement, and monito aquatic plant management activities to evaluate thei success. Lastly, emegent and floating-leaf plant beds, which have impotant benefits socially, ecologically, and

4 economically, wee mapped. Because lage aeas of emegent vegetation, specifically hadstem bulush, which once inged the shoeline have disappeaed on Wilkins Lake (MNDNR, 2006), an inventoy of the cuent status of these beds was desied. Methods: Staff pefomed a culy-leaf pondweed suvey on Wilkins and Whispeing Lakes on May 27, Suveyos navigated to aeas of the lake whee culy-leaf pondweed could possibly inhabit. Rake samples wee taken at 64 locations aound Wilkins Lake and 15 locations on Whispeing Lake in wate depths fom 3 to 10 feet (Figue 2). Rakes wee two metal gaden ake heads welded togethe at the top and attached to ope. Samples wee collected by dopping the ake into the sample aea, allowing it to touch bottom, and pulling the ake and attached vegetation up. The pesence o absence of culy-leaf pondweed was ecoded at each site. Figue 2. Location of Culy-leaf Pondweed Suvey fo Wilkins and Whispeing Lakes, Aitkin County. May 27, [ Seach Locations Wilkins Lake Outline with Contous Whispeing Lake Outline Also, a point-intecept vegetation suvey was pefomed on July 27 and 28, GIS (Geogaphic Infomation Systems) softwae was used to ceate suvey points that wee spaced 200 feet apat (Figue 3). The lake was plotted fom shoe to a depth of 30 feet to ensue enough samples wee collected to detemine the maximum depth of plant gowth. In the field, once the maximum depth of plant gowth was detemined, sites in deepe wate wee not sampled.

5 Figue 3. Vegetation Suvey Sample Gid and Actual Suvey Point Locations fo Wilkins and Whispeing Lakes, Aitkin County, Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y W Y Y Y Y [ Y Y Y Y N S Y Y Y Y E Y Y Sample Gid Y Suvey Points Wilkins Lake Whispeing Lake Suvey points wee loaded into a handheld GPS (global positioning system) unit fo navigating to sites fo sampling. All samples wee collected off the same side of the boat. At each site, a depth was ecoded fom an electonic depth finde. Suveyos ecoded the pesence of plants seen visually in the sampling aea (appoximately a 1 mete squae along the sampling side of boat) togethe with those collected fom a ake sample. Plants attached to the ake wee identified and included on the list of species pesent fo each suvey point. Afte collection fom the field, data was enteed into a compute speadsheet to be analyzed. Fo each lake a compaison of the fequency of aquatic plants by depth was plotted along with the common aquatic plants by depth of wate sampled. In addition, suveyos mapped floating-leaf and emegent vegetation stands. GPS data was collected, using a handheld unit, as the suveyos navigated aound the edges of vaious stands. A waypoint was taken whee the stand intesected the shoe, and at the beginning and end of each stand. The boundaies of stands wee mapped by saving a tack (a waypoint taken evey 3 seconds) with the GPS unit. Whee stands did not extend to shoe suveyos taveled aound the entie stand. New stands wee stated if the pevious stand physically ended, o a change in species composition was visible. Species pesence was ecoded fo each stand. Afte collection fom the field, data was enteed into a compute speadsheet to be analyzed. Also, GIS (Geogaphic Infomation Systems) softwae was used to complete the mapping.

6 Results: Suveyos did not find culy-leaf pondweed at any of the 79 locations that wee sampled on Wilkins and Whispeing Lake on May 27, In addition, no culy-leaf pondweed was sampled duing the point-intecept suvey pefomed on July 27 and 28, A total of 23 aquatic plants species wee collected duing the suvey, 17 species of submeged vegetation and thee each of floating-leaf and emegent vegetation (Table 1). One additional species of emegent plant, a type of aowhead (Sagittaia sp), was ecoded duing the emegent and floating-leaf bed mapping, but was not sampled duing the point-intecept suvey. Table 1. Fequency of Aquatic Plants, Wilkins Lake ( ) Aitkin County. July 27 and 28, Common Name Scientific Name 106 Total Samples Submeged Samples % Flat-stem pondweed * Potamogeton zosteifomis 48 45% Robbins pondweed * Potamogeton obbinsii 44 42% Coontail * Ceatophyllum demesum 43 41% Nothen watemilfoil Myiophyllum sibiicum 35 33% Clasping-leaf pondweed Potamogeton ichadsonii 20 19% Canada wateweed * Elodea canadensis 19 18% Lage-leaf pondweed * Potamogeton amplifolius 18 17% Naowleaf pondweed * Potamogeton sp % Vaiable pondweed Potamogeton gamineus 16 15% Wate maigold * Megalodonta beckii 13 12% Muskgass Chaa sp % Whitestem pondweed Potamogeton paelongus 11 10% Bushy pondweed Najas sp % Wild celey Vallisneia ameicana 10 9% White wate buttecup Ranunculus sp. 3 3% Wate stagass Zosteella dubia 3 3% Floating-leaf pondweed * Potamogeton natans 3 3% Floating-leaf Wateshield * Basenia schebei 13 12% Yellow watelily * Nupha vaiegata 10 9% White watelily * Nymphaea odoata 3 3% Emegent Cattail Typha sp. 2 2% Hadstem bulush Scipus acutus 2 2% Spikeush Eloechais sp. 2 2% * Indicates species sampled in Whispeing Lake (fequencies not calculated due to small sample size). Also, one aowhead species was sampled in Whispeing Lake.

7 The sample gid which was set up fo Whispeing Lake tun out not to be applicable due to the steep dop-off fom shoe to deep wate (which esulted in none of the sample gid points being in aeas with aquatic vegetation). Instead, suveyos collected eight samples fom vaious locations aound the peimete of Whispeing Lake. These samples collected 12 species of aquatic plants, 1 emegent species, 3 floating-leaf species, and 8 submeged species, all of which also occued in Wilkins Lake (Table 1). No additional analysis was pefomed on these data due to the small sample size. Theefoe, the emainde of this epot will focus on Wilkins Lake. The maximum depth that ooted aquatic plants wee sampled in Wilkins Lake was 15 feet, which esulted in a total of 106 vegetation samples. Vegetation was found at 86% of all the sample locations, and at 100% of the sites that occued in 6-10 feet of wate. A total of 8 samples wee collected in wate geate than 15 feet deep. No vegetation was found at any of these sites, theefoe they wee not used in calculating the fequency of occuence. The numbe of aquatic plant species sampled pe site deceased with inceasing wate depth (Figue 4). The divesity in the types of aquatic vegetation also displayed the same elationship. Emegent, floating-leaf, and submeged plant species wee sampled in shallow wate, no emegent plants wee found in wate deepe then 5 feet, and only submeged plants wee sampled in wate geate then 10 feet deep (Figue 5). Submeged plants whee the most widely vaied types of vegetation having the geatest numbe of species sampled in the widest vaiety of wate depths. Of the five most common aquatic plants sampled in Wilkins Lake, all wee submeged species (Figue 6). The fequency of occuence of flat-stem pondweed inceased as the wate depth inceased. The opposite was tue fo Elodea (Canada wateweed), with the highest Figue 4. Plant Abundance and Divesity vs. Wate Depth Wilkins Lake, Aitkin Co. ( ) July 27 and 28, 2005 % of sites with vegetation of species pe site % of sites with vegetation 100% 80% 60% 40% 20% 0% 0 to 5 6 to to to 20 wate depth (ft) of species pe site

8 Figue 5. Numbe and Type of Species Sampled in Wilkins Lake ( ) July 27 and 28, 2005 submeged floating-leaf emegent Numbe of Species ft 6-10 ft ft Wate Depth Figue 6. Common Aquatic Plants of Wilkins Lake, Aitkin Co. ( ) July 27 and 28, 2005 Fequency of Occuence to 5 6 to to 15 Wate Depth (ft) Flat-stem pondweed Robbins pondweed Coontail Nothen watemilfoil Claspingleaf pondweed Elodea

9 fequency of occuence found in the shallow depth wate and no plants being found in the 11 to 15 feet of wate (Figue 6). The othe thee most common aquatic plants of Wilkins Lake (Robbins pondweed, coontail and nothen watemilfoil) wee sampled in each of the depth anges, with the highest fequency of occuence was found in the 6 to 10 feet of wate ange fo each. Suveyos mapped 70 emegent and floating-leaf stands that coveed 15.9 aces on Wilkins Lake (Figue 7). Mixed vegetation beds wee mapped whee both types of vegetation occued in the same location, as well as whee emegent vegetation was obseved along shoe, but the density of the floating-leaf vegetation made navigating along that bode impactical. These mixed stands coveed a suface aea of aces, which epesented 68% of the total suface aea coveed by all stands. They occued most fequently in the westen potion of the lake. Emegent stands accounted fo 50% of the total numbe of stand, but only 19% (2.96 aces) of the total suface aea. Emegent and floating-leaf vegetation stands vaied geatly in density and composition aound the lake (Figue 8). Seveal natual factos influence the density of aquatic vegetation at diffeent locations within one lake. Lake mophology, the shape of the basin, limits aquatic plant gowth in aeas with steep slopes, and povides moe suitable habitat in aeas with gentle slopes to deep wate. Oientation of the lake, with espect to the pevailing wind diection, can influence the type of substate available fo aquatic plant ooting. Figue 7. Location of Emegent and Floating-leaf Vegetation Stands Wilkins Lake, Aitkin County August 12, 2005 Bed Types Emegent1.shp Emegent Floating-leaf Mixed Bed W E S Feet [ N

10 Figue 8. Natual Vaiation in the Density of Aquatic Vegetation Beds Mapped in Wilkins Lake, Aitkin County. August 12, Summay: The aquatic vegetation in Wilkins Lake includes a vaiety of plants native to the egion. Fisheies lake suveys fom the past had noted the pesence of the exotic species Culyleaf Pondweed. Howeve, no exotic species wee sampled duing the 2005 season.