Curly-leaf pondweed Density and Bed Mapping, and Warm Water Point Intercept Macrophyte Surveys Amnicon Lake - Douglas County, WI (WBIC: 2858100) Aerial Photo of Amnicon Lake (2010) Emergent and Floating-leaf plant communities in Amnicon’s southeast bay (Berg 2012) Project Initiated by: Amnicon Dowling Lake Management District, Short Elliot Hendrickson Inc., and the Wisconsin Department of Natural Resources * Amnicon Lake Floating-leaf bur-reed beds on the lake’s east side (Berg 2012) Survey Conducted by and Report Prepared by: Endangered Resource Services, LLC Matthew S. Berg, Research Biologist St. Croix Falls, Wisconsin May 19, 26, and August 3-4, 2012 TABLE OF CONTENTS Page ABSTRACT………………………………………………………………………… ii LIST OF FIGURES………………………………………………………………… iii LIST OF TABLES……………………………………….……………………….… iv INTRODUCTION.…..……..………………………………………………………. 1 METHODS……………………………..…………………………………………... 2 DATA ANALYSIS….……………………………………………………………... 3 RESULTS.…………..…………………………………………………………….... 6 DISCUSSION AND CONSIDERATIONS FOR MANAGEMENT…..…..…….… 24 LITERATURE CITED……………………….…………………………….………. 28 APPENDIXES…….…………………………………………………….………….. 29 I: Amnicon Lake Map with Sample Points……………..……………………….. 29 II: Boat and Vegetative Survey Data Sheets……………….…………………….. 31 III: May CLP Density and Distribution and Bed Maps…………………..………. 34 IV: Habitat Variable Maps.…………………..………….……………………....... 37 V: Native Species Richness and Total Rake Fullness Maps.………………..…... 41 VI: Amnicon Lake Plant Species Accounts ……………………………….……... 44 VII: Amnicon Lake P/I Density and Distribution Maps………………...…............ 58 VIII: Aquatic Exotic Invasive Plant Species Information.………………………… 112 IX: Glossary of Biological Terms……………..……………………….……….… 120 X: Raw Data Spreadsheets…….……………..……………………….……….… 124 i ABSTRACT Amnicon Lake (WBIC 2858100) is a 390-acre stratified drainage lake located in west-central Douglas County, WI. The lake is mesotrophic with a littoral zone that reached 11ft. in 2012. As a prerequisite to developing an Aquatic Plant Management Plan, the Amnicon Dowling Lake Management District, Short, Elliot, Hendrickson, Inc., and the Wisconsin Department of Natural Resources authorized Curly-leaf pondweed (Potamogeton crispus) density and bed mapping surveys on May 19th and 26th, and a full point intercept survey from August 3-4, 2012. In May, we found CLP at seven sample points or 1.4% of the lake. Of these, three (0.6%) had a rake fullness of 2 or 3 indicating a significant infestation. We also mapped 3 beds totaling 5.36 acres and covering 1.4% of the lake. During the August survey, there were macrophytes growing at 218 sites or 43.5% of the entire lake bottom and in 77.9% of the littoral zone. Overall diversity was extremely high with a Simpson Diversity Index value of 0.94. Of the 60 species found growing in and immediately adjacent to the lake, Nitella (Nitella sp.), Coontail (Ceratophyllum demersum), Wild celery (Vallisneria americana), and Flat-stem pondweed (Potamogeton zosteriformis) were the most common macrophyte species being found at 40.83%, 35.32%, 29.36%, and 28.44% of survey points with vegetation. The 46 native index species found in the rake during the August survey produced an above average mean Coefficient of Conservatism of 6.8 and a Floristic Quality Index of 45.9 that was nearly double the median FQI for this part of the state. Other exotic species found included Reed canary grass (Phalaris arundinacea), Purple loosestrife (Lythrum salicaria), Common forget-me-not (Myosotis scorpioides), Joint rush (Juncus articulatus), and Narrow-leaved cattail (Typha angustifolia) although none of them appeared invasive at this time. Future management considerations include working to preserve native plants and the critical habitat they provide for the whole lake ecosystem; improving water clarity and decreasing algal growth; encouraging all lakeshore property owners to proactively reduce nutrient runoff and erosion by not mowing down to the water, bagging grass clippings, eliminating fertilizer applications near the water, restoring shorelines, and establishing buffer strips of native vegetation; placing slow/no wake buoys near the Northern wild rice (Zizania palustris) beds on the south side of the lake to better protect them during their floating-leaf stage; continuing to monitor the CLP beds for expansion; and working to prevent the spread of CLP by refraining from removing native plants and which can expose the lake substrate making it easy for CLP to establish. At the public boat landings, continuing the established Clean Boats/Clean Waters Program; improving the current signage to remind boaters of the dangers/impacts of AIS; and conducting monthly landing and annual whole lake visible littoral zone surveys for AIS are all management strategies for the ADLMD to consider as they develop their APMP. ii LIST OF FIGURES Page # Figure 1: Amnicon Lake Aerial Photo…………………………………………….. 1 Figure 2: Rake Fullness Ratings…………………………………………………… 2 Figure 3: Amnicon Lake’s May CLP Density and Distribution …………………... 6 Figure 4: Amnicon Lake May CLP Bed Map……………………………………... 7 Figure 5: Survey Sample Points and Lake Depth………………………..………… 8 Figure 6: Bottom Substrate and Littoral Zone……………………………..……..... 9 Figure 7: Native Species Richness and Total Rake Fullness………………………. 10 Figure 8: Amnicon Lake’s Most Common Macrophyte Species……..……....…… 18 Figure 9: Amnicon Lake’s May/August CLP Density and Distribution.………….. 21 Figure 10: Purple Loosestrife and Galerucella Beetles……………………...….…. 22 Figure 11: Amnicon Lake’s Filamentous Algae Density and Distribution…..….… 22 Figure 12: Amnicon Lake’s Northern Wild Rice Density and Distribution.……..... 23 Figure 13: Low Density Wild Rice South of Tomahawk Island……...………….... 23 Figure 14: Model Natural Shoreline vs. Mowed Down to the Shore/Erosion…….. 24 Figure 15: Bright Signage at a Barron Co. Public Boat Landing……………….…. 26 iii LIST OF TABLES Page # Table 1: CLP Bed Summary Amnicon Lake, Douglas County May 26, 2012…….. 7 Table 2: Aquatic Macrophyte P/I Survey Summary Statistics Amnicon Lake, Douglas County August 3-4, 2012..……………………………….. 9 Table 3: Frequencies and Mean Rake Sample of Aquatic Macrophytes Amnicon Lake, Douglas County August 3-4, 2012……………………………..…. 15 Table 4: Floristic Quality Index of Aquatic Macrophytes Amnicon Lake, Douglas County August 3-4, 2012….………………………….….. 19 iv INTRODUCTION: Amnicon Lake (WBIC 2858100) is a 390-acre stratified drainage lake located in the Town of Summit in west-central Douglas County (T46N R14W S14 SE NE). The lake reaches a maximum depth of 31ft near the north-central shore and has an average depth of 10ft (WDNR 2009) (Figure 1). The lake is mesotrophic bordering on eutrophic in nature with fair water clarity that produced Secchi reading averaging 5.3ft from 1991-2011 (WDNR 2012). However, during the 2012 surveys, readings varied from 6ft in May to little more than 3ft in August. These conditions produced a littoral zone that extended to 11ft. Bottom substrate was predominantly organic muck in the sheltered bays of the south and west, and a mixture of sand, rock, and sandy muck on the north and east shorelines, midlake bars, and around Little and Tomahawk Islands (Ginder et al. 1971). Figure 1: Amnicon Lake Bathymetric Map The Amnicon Dowling Lake Management District (ADLMD), Short Elliot Hendrickson, Inc. (SEH), and the Wisconsin Department of Natural Resources (WDNR) authorized a series of full lake plant surveys on Amnicon Lake in 2012 prior to developing an Aquatic Plant Management Plan for the lake. On May 19th, we completed a cold water Curly-leaf pondweed (Potamogeton crispus) (CLP) point intercept survey. This was followed by a CLP bed mapping survey on May 26th, and a warm water point intercept survey of all aquatic macrophytes on August 3rd and 4th. Both point intercept surveys used the WDNR’s statewide guidelines for conducting systematic point intercept macrophyte sampling. These methods ensure that all surveys in the state will be conducted in the same manner, thus allowing data to be compared across time and space. The immediate goals of the surveys were to determine if CLP or Eurasian water milfoil (Myriophyllum spicatum) had invaded the lake, and to establish data on the richness, diversity, abundance and distribution of other native aquatic plant populations. These data provide a baseline for long-term monitoring of the lake’s macrophyte community as well as a way to measure any impacts on the lake’s plants if active management occurs in the future. 1 METHODS: Curly-leaf Pondweed Point Intercept Survey: Using a standard formula that takes into account the shoreline shape and distance, islands, water clarity, depth and total acreage, Michelle Nault (WDNR) generated a 501 point sampling grid for Amnicon Lake (Appendix I). Using this grid, we completed a density survey where we sampled for CLP at each point on the grid. We located each survey point using a handheld mapping GPS unit (Garmin 76CSx), and used a rake to sample an approximately 2.5ft section of the bottom. CLP was assigned a rake fullness value of 1-3 as an estimation of abundance (Figure 2). We also recorded visual sightings of CLP within six feet of the sample point. Figure 2: Rake Fullness Ratings (UWEX, 2010) CLP Bed Mapping Survey: Following the CLP density survey, we used the resulting map coupled with a meandering littoral zone search to locate and delineate all significant beds of CLP on the lake. We defined a bed based on the following two criteria: CLP plants made up greater than 50% of all