Devils Lake Annual Report 2011

Transcription

1 Devils Lake Annual Report 2011 Prepared for the Rollin Township and Woodstock Township Boards by: Savin Lake Services 3088 Hottis Road Hale, MI 48739

2 Jan. 9 Table of Contents Devils Lake Annual Report Introduction Survey... 5 Water Quality...14 Recommendations...20 Costs...24 Conclusion...28 Appendix I - EnviroScience 2011 Devils Lake Weevil Population Report Appendix II - Naturally, Inc. Suction Harvesting Report Appendix III - Genetic Testing Results from Dr. Ryan Thum 2

3 Devils Lake Annual Report Introduction "Devils Lake is a 1,330-acre recreational lake in southeastern Michigan near the Ohio border. Devils Lake lies in a region that was once inhabited by a Native American tribe known as the Potawatomi. According to legend, the lake was named by a Potawatomi leader who believed that the waters were inhabited by evil spirits when his daughter drowned in the lake and her body was never recovered." 1. "Devils Lake is a 1337-acre moderately hard water kettle lake located in Sections 26, 27, 34 and 35, Woodstock Township (T5S R1E) and Sections 2, 3, 4, 9 and 10, Rollin Township (T6S R1E), Lenawee County, Michigan. The lake consists of a 755-acre. 63-foot deep north basin which contains acre feet of water and a 579 acre, 58-foot deep south basin which contains 6540 acre feet of water, separated by a shelf less than four feet deep. The total lake volume is acre feet. The mean depth is 14.2 feet. About 52 percent of the north basin and 65 percent of the south basin is ten feet deep or less. The lake has feet of shoreline. The elevation of the lake is 1043 feet above sea level." LakeLubbers.com 2. Dr. Wallace Fusilier, Ph.D., Consulting Limnologist 3

4 Jan. 9 Devils Lake Annual Report One of the major sources of water for Devils Lake in Lenawee County is Horton Drain which flows into the lake on the north end. The size of the area drained by Horton Drain is 2748 acres, or 4.3 square miles. (See map below.) 4

5 Devils Lake Annual Report Survey Devils Lake was surveyed during the first two weeks of June, A specially outfitted Savin Lake Services survey boat was deployed for conducting the survey using a Raven Viper 2 precision GPS instrument and a Raven "Cruizer" capable of data logging both the boat path and the presence of aquatic vegetation. The data was collected onto Compact Flash based memory cards, transferred to awaiting Personal Computers, and dropped into a series of mapping programs to create the final graphical displays. The collected data remains in a specialized and proprietary format throughout the entire process and is immune to tampering or alteration. Google Earth Pro TM was also used in preparing some of the final images utilizing Google's direct import routines. The surveying began in early June. This was accomplished during five survey dates: June 2, 2011 June 3, 2011 June 8, 2011 June 10,2011 June 17, 2011 A specially outfitted 20 foot Sea Ark boat with a four-stroke 90 horsepower Mercury motor survey boat was used in conducting the survey. Weather played a major factor in determining the survey dates as surveying was only done during optimal sighting conditions assuring accurate and comprehensive results. Rather than use an Aquatic Vegetation Assessment Site (AVAS) protocol or a Point Intercept Grid method, Savin Lake Services employed the use of Differential Global Positioning Systems (dgps) resulting in over one hundred thousand recorded grid-points on Devils Lake. Utilizing the data logging characteristics of the Raven Viper 2 integration GPS field computer, and being guided by the Raven "Cruizer", the boats made hundreds of 100 foot wide passes in an east/west direction. This was repeated until the entire lake was surveyed. Using the information saved from each survey, the boat could easily be placed and surveying could continue precisely where the previous job had concluded. CALIBRATION The Raven Cruizer unit was set up to data log the boat path during the entire survey. Waypoints were created at the three water sampling locations (flags 3, 4, and 5 respectively) while the remaining four waypoints represent collection stations for the 5

6 Jan. 9 Devils Lake Annual Report Watermilfoil that was genetically tested. The boat path was logged by painting a 100 foot wide swath of the lake for each east/west pass. Because of the accuracy of the Wide Area Augmentation System (WAAS) enabled GPS units, the level of control of the boat paths was extraordinary. There were actually over 126,000 data points referenced in the final combined job files representing the survey path of the boat. (Actual boat path from data logging) 6

7 Devils Lake Annual Report Similarly, the Raven Viper 2 unit was set up to data log both the native aquatic vegetation and exotics, specifically Watermilfoil. This was accomplished utilizing two channels on the Viper 2. A complete mapping of the lake including the exact location and size of the Watermilfoil beds was accomplished using the primary data logging channel within the Viper 2. Using polarized glasses, Savin Lake Services certified aquatic weed specialists activated the primary data logging channel upon the presence of Milfoil and similarly deactivated it at the end of the weed bed. Native aquatic vegetation was mapped accordingly with the same accuracy on the secondary channel. Overlaying the data from both recording channels allowed for pinpoint accuracy when mapping the locations of the milfoil beds. COMPILATION Data was recorded in job files onto Compact Flash memory cards using the Raven Viper 2 data logging capabilities and the data was immediately backed up and archived onto our main computer system each survey evening. Generational files were saved for safe keeping as the Viper 2 appends new data onto the existing job file. The data is saved in a Shapefile (SHP) format. This format contains geospatial vector data for Geographic Information Systems (GIS) software. The information cannot be altered without destroying the integrity of the shapefile. This is a very popular file format for this type of information as it is easily imported into a variety of software packages specifically created for geographic information illustrations. Three software programs were used during the final compilation of the data. The first program is provided by Raven Industries, the producers of the Raven Viper 2 precision control units, and is simply a data decompression utility. This utility takes the compressed data and writes it out into machine-readable files for further use in database or graphic programs. In addition to database files which log the exact location of each entry point every second, it also contains that data logging files referencing the boat path information and weed sighting information. Furthermore, the shapefiles are extracted with this utility as well. Savin Lake Services uses a CAD program for reading the shapefile data and displaying it graphically. The program supports full Geographical Information System (GIS) data mapping as well as other output formats such as Geo-JPEG with maintains the geographical data in an easy to view industry standard JPEG format. It also offers enhanced versatility supporting a variety of file types so that we can easily import the logged data and overlay it onto to a GIS referenced map or even a Google Earth Pro TM file. This product can be used to create treatment maps for our customers as well. Recent improvements in Google Earth Pro TM 's import technology has dramatically improved our data handling methodology. We can import the output files from the Raven GPS units directly into Google Earth Pro TM which allows for direct data transfer 7

8 Jan. 9 Devils Lake Annual Report into the final presentations. This assures the greatest level of accuracy and data chain of custody. Once the whole lake survey was verified to assure that there were no missed survey points, the logged data representing the existence of aquatic vegetation was analyzed in the same controlled manner. Although far from a finished product, the absolute raw data gave us an initial rendering as follows: Raw GPS output of Native Vegetation Channel from Raven Viper 2. 8

9 Devils Lake Annual Report Raw GPS output of WaterMilfoil Channel from Raven Viper 2. 9

10 Devils Lake Annual Report Jan. 9 Combined Native and WaterMilfoil data set imported into Google Earth ProTM. White indicates native vegetation. Red indicates WaterMilfoil. 10

11 Devils Lake Annual Report Hydrographic Map illustrating the milfoil beds. Red areas indicate small patches of isolated WaterMilfoil. 11

12 Jan. 9 Devils Lake Annual Report Extrapolating actual WaterMilfoil beds from the raw data yielded these final results: WaterMilfoil bed boundaries were graphically converted from the raw data in weed bed boundaries that could then be calculated down to the square foot in accuracy. The identified bed sizes were calculated to scale and 22 quantifiable weed beds were used to arrive at the final calculation. Areas that were considered Found (covering 2%< of the swath surface area) were not counted as a quantifiable weed bed and were only considered when their rapid increase in density indicated the beginning of an adjacent bed. 12

13 Devils Lake Annual Report Hydrographic Map illustrating the milfoil beds and native/non-native plants. The total Aquatic Vegetation area is nearly 300 Acres. ( Acres). 13

14 Jan. 9 Water Quality Devils Lake Annual Report Water quality samples were taken from three sampling sites on Devils Lake. On the boat path map (page 6), the samples were taken at the sites at flag positions 3, 4, and 5. Waypoint flag position 7 was a calibration cross-reference entry and serves no purpose in the samples. Samples were collected on two days during the summer months of The first collection was on June 16 while the second occurred on August 24. Three surface samples were taken each day (one from each of the 3 locations.) Dissolved oxygen, temperature, and secchi disk readings were recorded in-situ. Water samples were sent to the Michigan Water Research Center at Central Michigan University to determine the remaining parameters consisting of chlorophyll a, nitrate, alkalinity, ph, conductivity, and phosphorus. Temperature and Dissolved Oxygen Temperature and dissolved oxygen content in water affects many functions in a body of water. Temperature directly affects the amount of dissolved oxygen in water. Warmer waters hold less oxygen than colder water. Stratification of the water column in summer occurs from temperature differences as well. Fish and other marine life are very sensitive to temperature changes and only live comfortably in particular ranges of it. Similarly, but to more of an effect, dissolved oxygen plays a significant role in many aspects of water. It is used by fish and other animals to live, affects chemical processes such as release and precipitation of iron from sediments, and also drives aerobic decomposition of organic matter in lakes. Thus, in most lakes, but to a far greater extent in poor quality lakes, dissolved oxygen is absent below the thermocline due to stratification and the abundance of dead plant matter at the bottom of a lake. Since dissolved oxygen is relative to the temperature of water, the amount of oxygen in a lake is often looked at in terms of percent saturation. Therefore, it can be easily determined how much oxygen is present relative to the appropriate amount for that temperature. Temp (ºC) Devils Lake 2011 Temperature 14

15 Devils Lake Annual Report The graphs for Devils Lake show values as expected from a normal quality lake. As the temperature of the water increases from June to August, the dissolved oxygen concentration decreases from an average of 9.4 mg/l to 8.3 mg/l. Using the temperature and concentration of dissolved oxygen in the water, the percent saturation of oxygen decreases from an average of 108% to 101%. These are good readings. % saturation Devils Lake 2011 Dissolved Oxygen Secchi Disk The use of a Secchi disk determines the clarity of a body of water. Readings are most accurate when lowering the disk on the shaded side of a boat, on a calm and sunny day. If it is not cloudy, or if it is windy, a shallower depth may be recorded. To obtain a measurement, lower the Secchi disk into the water until it disappears. Then raise the disk until it reappears. Raise and lower the disk until the exact depth of reappear/disappear is found. This is the depth recorded. Generally higher quality lakes have greater recorded depths then poorer quality lakes. This test should not be used if the bottom of the lake can be seen. Depth (ft) Devils Lake 2011 Secchi Disk Secchi disk readings were not available for the first two sampling sites in August. In June, Devils Lake had an average depth of 11 feet. This is seems consistent to slightly shallow compared with data from previous years. 15

16 Jan. 9 Chlorophyll a Chlorophyll a is used to determine the amount of plants and algae in a lake. If the concentration of chlorophyll a is high in water, that can mean high biological activity. That can lead to, or be an indicator of, poor water quality. Devils Lake Annual Report Concentration (ug/l) Concentration (ug/l) Devils Lake 2011 Chlorophyll a On Devils Lake, June samples were not adequate to retrieve August chlorophyll a data; however, concentrations were obtained from the August samples. Samples ranged from 4.2 to 3.1 ug/l and averaged 3.6 ug/l. Phosphorus Phosphorus is very important to water quality. Phosphorus is used by plants during photosynthesis, thus it is needed for plants and algae to grow. Although there are many different forms of phosphorus, each one can change to another form. Therefore all phosphorus species can be used by plants. Used as a fertilizer, runoff can transport phosphorus into nearby lakes and streams causing algal Devils Lake 2011 Phosphorus blooms. However, phosphorus is used by humans in many different ways, not just in fertilizer. Phosphorus in Devils Lake ranged from 14 to 23 ug/l in June and averaged 20 ug/l. In August the values ranged from 17 to 20 and averaged 18 ug/l. These are fairly normal values for phosphorus. 16

17 Devils Lake Annual Report Carlson s Trophic State Index The Carlson s Trophic State Index is a rough way to determine how eutrophic a lake is. Eutrophication is the accumulation of plant material due to an increase volume of nutrients. It is a natural process but is sped up by humans by nutrient loading lakes. The index takes 3 parameters (Chlorophyll a, phosphorus, and secchi disk depth) and using a formula, gives a value that relates to a specific trophic state. TSI values of less than 40 associates with oligotrophic lakes, which produce low amounts of plant mass (nutrient poor). TSI values greater than 50 associates with eutrophic lakes, which produce high amounts of plant mass (nutrient rich). TSI values of are mesotrophic lakes and are moderate in plant mass. This does not mean a lake is high or low quality necessarily, but gives a good estimation. Accompanied with other information such as dissolved oxygen and nitrogen, a determination can be made as to the quality of the lake. The formulas for calculating the TSI are (ln is the natural log function): TSI= ln (Secchi disk in meters) TSI= 9.81 ln (chlorophyll a in ug/l) TSI = ln (total phosphorus in ug/l) Devils Lake s TSI values (using average values) in June were 42.3 (Secchi), N/A (chlorophyll a), and 47.1 (phosphorus). The August values were 45.5, 43.2, and 45.8 each. Thus, Devils Lake can be considered a mesotrophic lake since all TSI values were between 40 and 50. Nitrogen Nitrogen is also used in many ways in a water body, and is important for plant growth. Phosphorus and nitrogen are two of the most important nutrients (limiting nutrients) in water quality. Nitrogen is used to build plant material and phosphorus is used for energy (food) in plants. Concentration (ug/l) Devils Lake 2011 Nitrate Nitrogen Devils Lake s nitrogen levels are low. The June levels ranged from 27 to 29 ug/l while the August values were all below 1 ug/l. The reason for the near 0 values in August may be because as plants grow in the summer they remove nitrogen that is in the water. All these values are good. 17

18 Jan. 9 Alkalinity Devils Lake Annual Report Alkalinity is the measure of how hard water is. This means it is the measure of how well water neutralizes acids. A high amount of carbonate species in means the water is hard. An acid can be thought of as a hydrogen ion, like hydrochloric acid (HCl). Generally, when the acid enters water, the hydrogen splits from the rest of the acid, such as H + and Cl -. Thus, more acid means more H +. Alkalinity buffers the acid, stripping the H + from the water, resisting a drop in the ph. In Michigan, most lakes are moderately hard (60 to 120 mg/l) to very hard (>180 mg/l) due to the ground. Concentration (mg/l) Devils Lake 2011 Alkalinity Devils Lake is a moderately hard lake. From the 2011 data, June figures ranged from 106 to 108 mg/l while August ranged from 118 to 120 mg/l. All values are at the high end of a moderately hard lake. Hydrogen Ion Concentration (ph) The ph of a lake is a rough measure of its quality. Many factors influence the ph of a lake, such as alkalinity. Rain is almost always acidic, and even more so in close proximity to cities and factories. One reason Michigan lakes usually have ph levels from 7 to 9 is because of the alkalinity. Devils Lake 2011 ph Devils Lake has a ph range of to 7.62 in June, and a range 7.77 to 8.18 in August. Notice the correlation between higher alkalinity and higher ph in August. (More alkalinity strips H + from water, thus raising ph.) This is normal for a moderately hard Michigan lake. 18

19 Devils Lake Annual Report Conductivity The conductivity of the water is the measure of how well the water conducts an electrical current. Pure water will not conduct electricity. Therefore this tells us how much dissolved material is in the water. Generally, higher dissolved material indicates poorer quality. Thus, a higher conductivity reading indicates poorer quality. Devils Lake in June 2011 ranges from 251 to 282 umhos/cm and average 266. August ranges from 259 to 285 umhos/cm and averages 269. These values are normal. Compiled Data (umhos/cm) Devils Lake 2011 Conductivity Below is a table of collected data from 2011 of all parameters tested. Overall, Devils Lake s quality seems in balance at a moderate nutrient bearing lake. There is a presence of plant activity that neither has a strong push to dwindle or grow. However, human influence can greatly disrupt this balance and precautions must always be used to preserve our lakes. 19

20 Jan. 9 Devils Lake Annual Report Devils Lake Management Recommendations Savin Lake Services is recommending three (3) options for managing Devils Lake during the 2012 through 2014 timeframe. Several factors were considered when developing the options matrices below including but not limited to: Past reports from various consultants. Water Quality Studies from Dr, Wallace Fusilier. Genetic makeup of the WaterMilfoil. Past experiences working with both Enviroscience (weevils) and "Naturally", LLC (suction harvesting). The data produced for this report. Residential sensitivity to the use of aquatic herbicides. Historical efficacy regarding each treatment method both exclusively and as a part of an integrated solution. Budgetary constraints of the funding mechanisms. With this in mind, the following three options are recommended in an order from optimal to satisfactory: Optimal Solution: Aquatic Herbicides Yes Yes No Mechanical Harvesting No Yes Yes Weevils No TBD TBD Suction Harvesting No Yes Yes Consulting/Mapping Yes Yes Yes The use of aquatic herbicides, although opposed by some, is still the most commonly used method for controlling aquatic nuisance plant species. The costs are less expensive and the herbicide can be directly applied to the problem vegetation. The granular aquatic herbicide known as 2,4-D (like Navigate) can actually systemically kill many varieties of WaterMilfoil if applied at the rate of 200 pounds per acre. A systemic kill would be the complete elimination of the plant, including the root system so that it does not return the following year. Although most varieties of WaterMilfoil can rarely be 20

21 Devils Lake Annual Report completely eradicated, the use of 2,4-D can quickly free up vast areas of the waterbody for recreational use while maintaining an ecological balance. Granular Triclopyr (like Renovate OTF) is an aquatic herbicide that is an alternative to 2,4-D and is also very effective on a number of invasive species and targeted weeds. Although it does not share the same water well restrictions as 2,4-D, it does have a much longer restriction on un-established turf and forage irrigation. Mechanical harvesting has also been recommended. There are a number of advantages of using mechanical harvesting and a few disadvantages as well. Mechanical harvesting results in immediate results and open water. It can also reduce nutrient loading by not only removing phosphate loaded biomass, but also reducing the amount of plant material available for sedimentation buildup. The lower part of the plant remains for fish habitats and harvesting can be directly targeted by mechanical means. Some of the disadvantages to mechanical harvesting are that they are difficult to maneuver around docks and in shallow water, a small amount of cuttings are missed by the collection conveyor and eventually end up on shore, and fragmentation plants could even be spread by the cutting process. Watermilfoil is basically an auto-fragmentation plant and years ago, many lake managers felt that harvesting an auto-fragmentation plant simply exacerbated the situation. Recent results during the past few years however, have swayed many into believing that by mechanically harvesting the Milfoil, the invasive is still being reduced by a great degree and with the reduction in biomass, an obvious advantage is realized. The plant will auto-fragment by natural means or from normal recreational activities anyway, so Savin Lake Services also subscribes to this belief that at least cutting and removing the majority of the plant is far superior to doing nothing whatsoever. Being a cutting process by nature however, the plants do eventually grow back. The continued use of weevils (Euhrychiopsis lecontei) on Devils Lake is not recommended for 2012 as we are recommending herbicide control; however, the continued use of weevils beyond 2012 may help in controlling the nuisance vegetation. The genetic testing of the Watermilfoil in Devils Lake has shown Variable Watermilfoil are not conducive to weevil treatment which specialize on Eurasion Watermilfoil and high-percentage Eurasion-based Hybrids. Suction harvesting offers an interesting alternative to the aforementioned methods. Diver-assisted suction harvesting can be very selective and if properly executed, the removal can be very effective with very little re-growth. One disadvantage is that it can be very slow thus contributing to the second disadvantage of being rather costly. It is however, an excellent method for small areas that are too large for hand harvesting, yet too small for other means of control. 21

22 Jan. 9 Option 2 - No aquatic herbicides. Devils Lake Annual Report Aquatic Herbicides No No No Mechanical Harvesting Yes Yes Yes Weevils TBD TBD TBD Suction Harvesting Yes Yes Yes Consulting/Mapping Yes Yes Yes Option two (2) offers a nearly identical treatment regime without the use of aquatic herbicides during any of the treatment years. The combination of the two harvesting techniques used in tandem and in junction where the methods' natural strengths lie would prove to be a very viable solution. The disadvantages of each method could be mitigated through the use of selective harvesting techniques and costs could be controlled by effectively plotting and planning the cutting operations. Option 3 - Suction Harvesting (& Potential Weevil Augmentation) Aquatic Herbicides No No No Mechanical Harvesting No No No Weevils TBD TBD TBD Suction Harvesting Yes Yes Yes Consulting/Mapping Yes Yes Yes Option three (3) is going to be the most restrictive option in terms of total acreage addressed. Budgetary limitations would require some difficult decisions be made regarding the number of acres that can be effectively managed. Please refer to the pricing section to gauge the impact of a suction harvesting exclusive alternative. 22

23 Devils Lake Annual Report Treatment Expenditures Aquatic Herbicides - Using 2,4-D or Triclopyr at the prescribed rates will cost approximately $ per acre plus Michigan DEQ permit fee.. Mechanical Harvesting - The use of a mechanical harvester, including removal and disposal of the spoils is $ per acre. Weevils - Please refer to the attachment from Enviroscience regarding the specifics and options regarding the use of weevils on Devils Lake. Each year's costs includes all direct costs, mapping, surveys, and reports Weevil costs will range from $13, to $21, Weevil costs will range from $13, to $21, Subsequent years of mapping, surveying, and reporting would be approximately $1, per year. Suction Harvesting - Please refer to the attachment from Naturally LLC regarding suction harvesting. For the suction harvesting, including spoils removal and de-watering is approximately $0.60 per square foot for areas less than one (1) acre in size or $15, per acre plus the Michigan DEQ permit fee (if required). The per acre fee is highly discounted from the square foot rate. Consulting and Mapping - Annual Consulting and Mapping charges will be $11, per year. 23

24 Jan. 9 Devils Lake Annual Report Current Special Assessment District Budget Constraints: BUDGETING PARAMETERS As Rollin and Woodstock Townships are collaborating the management and treatment of Devils Lake under Public Act 188 budgeting parameters have been developed with the inclusion of both townships. Since both townships operate in arrears, budgeting parameters would be structured as follows: Annual Funding (per Township Treasurers) Woodstock Rollin Combined $ 42, (max.) $ 46, $ 89, Recommended Expenditures Based Upon Current SAD Constraints Optimal Solution 2011 (Actual) Aquatic Herbicides $0.00 $77, $40, $0.00 Mechanical Harvesting $0.00 $0.00 $37, $32, Weevils-Surveying $1, $0.00 $0.00 $22, Suction Harvesting $45, $0.00 $0.00 $22, Consulting/Mapping $11, $11, $11, $11, Total $57, $89, $89, $89, Option 2 - No aquatic herbicides Aquatic Herbicides $0.00 $0.00 $0.00 Mechanical Harvesting $77, $51, $51, Weevils $0.00 $13, $13, Suction Harvesting $0 $13, $13, Consulting/Mapping $11, $11, $11, Total $89, $89, $89,

25 Devils Lake Annual Report Option 3 - Suction Harvesting (& Potential Weevil Augmentation) Aquatic Herbicides $0.00 $0.00 $0.00 Mechanical Harvesting $0.00 $0.00 $0.00 Weevils $2, $2, $2, Suction Harvesting $75, $75, $75, Consulting/Mapping $11, $11, $11, Total $89, $89, $89, The total amount allocated to Suction Harvesting represents approximately 5 (five) acres of total suction harvesting. The $ Weevils allocation is for population studies and stem density reports. Recommended Annual Expenditures by Solution, by Township, by Year based upon Current Budget Optimal Solution Option 2 - No Herbicides Option 3 - Suction Only Rollin Woodstock Rollin Woodstock Rollin Woodstock 2012 $46, $42, $46, $42, $46, $42, $46, $42, $46, $42, $46, $42, $46, $42, $46, $42, $46, $42,

26 Jan. 9 Devils Lake Annual Report Future Recommended Special Assessment District Budget Structure: It is well understood that the contributing percentages to addressing aquatic weed issues in Devils Lake is as follows: Rollin Township: 76% Woodstock Township: 24% Savin Lake Services recommends a management and treatment budget of $130, for the total annual management cost for both native and non-native nuisance plant management. Applying the above percentages, the recommended annual lake management costs would be: Rollin Township: $ 98, Woodstock Township: $ 31, Current budgeting parameters differ greatly from the current recommendations and this is addressed in the following sections. Recommended Expenditures: (Based on Future Revised SAD Structure) Optimal Solution (Actual) Aquatic Herbicides $0.00 $118, $0.00 $0.00 Mechanical Harvesting $0.00 $0.00 $58, $58, Weevils-Surveying $1, $0.00 $0.00 $0.00 Suction Harvesting $45, $0.00 $60, $60, Consulting/Mapping $11, $11, $11, $11, Total $57, $130, $130, $130,

27 Devils Lake Annual Report Option 2 - No aquatic herbicides Aquatic Herbicides $0.00 $0.00 $0.00 Mechanical Harvesting $88, $58, $58, Weevils $0.00 $0.00 $0.00 Suction Harvesting $30, $60, $60, Consulting/Mapping $11, $11, $11, Total $130, $130, $130, Option 3 - Suction Harvesting (exclusively) Aquatic Herbicides $0.00 $0.00 $0.00 Mechanical Harvesting $0.00 $0.00 $0.00 Weevils $0.00 $0.00 $0.00 Suction Harvesting $118,385.00* $118,385.00* $118,385.00* Consulting/Mapping $11, $11, $11, Total $130, $130, $130, *This figure equates to approximately 7.89 acres of treatment. Mechanical Harvesting rates in the Optimal Solution remain consistent even after the Aquatic Herbicide application in 2012 so that the levels of native Elodea (elodea canadensis), native Sago Pondweed (Stuckenia pectinata), non-native Curlyleaf Pondweed (potamogeton crispus), and native Illinois Pondweed (potamogeton illinoensis) that was found and logged on a grid map of Devils lake during the survey. Likewise, as an alternative to Aquatic Herbicides in Option 2, nearly 285 acres would be harvested in 2012 to address all of the WatermilFoil beds and the unwanted aquatic vegetation as per the combined mapping seen on page

28 Jan. 9 Devils Lake Annual Report Recommended Annual Expenditures by Solution, by Township, by Year Optimal Solution Option 2 - No Herbicides Option 3 - Suction Only Rollin Woodstock Rollin Woodstock Rollin Woodstock 2012 $98, $31, $98, $31, $98, $31, $98, $31, $98, $31, $98, $31, $98, $31, $98, $31, $98, $31, Conclusion As your lake management consultant, Savin Lake Services is pleased to offer these recommendations. It is readily apparent that any solution involving the current Special Assessment District constraints does not represent the 76% to 24% split (Rollin Township, Woodstock Township respectively) however the current underfunding status would require maximizing Woodstock Township s assessment district contribution and/or re-evaluating Rollin Township s contribution levels. The current recommendations and township contribution levels are solely based upon current Special Assessment District levels. A revised Special Assessment District in Rollin Township would be required in order to fully fund the project to recommended levels while reconciling the 76% to 24% township funding burden. 28

29 Devils Lake Annual Report Appendix I EnviroScience Devils Lake Weevil Population Report

30 2011 Weevil Population Survey in Devils Lake Prepared for: Rollin and Woodstock Townships Manitou Beach, Michigan Prepared by: EnviroScience, Inc., 3781 Darrow Road, Stow, Ohio (800) October 10, 2011

31 " E x c e l l e n c e i n E c o l o g i c a l M o n i t o r i n g " I. Introduction This report is a summary of the 2011 weevil population survey on Devils Lake, Manitou Beach, Michigan. The native North American milfoil weevil (Euhrychiopsis lecontei), was augmented in three sites in 2010 to suppress the growth of Eurasian watermilfoil (Myriophyllum spicatum) (hereafter referred to as EWM), an invasive aquatic macrophyte. EnviroScience performed a survey of three sites on Devils Lake in 2011 to assess the weevil population. The milfoil weevil is a specialist herbivore of Eurasian watermilfoil, but has also been shown to successfully suppress hybrid milfoil, which is a cross between Eurasian watermilfoil and native Northern watermilfoil (M. sibiricum). The most significant impact is caused by weevil larva as they damage the meristem, or growing tip, and burrow through the stem. Nutrient flow in the plant is disrupted and the stem loses buoyancy and eventually collapses in the water column. A cascading effect pulls neighboring plants lower into the water column as stems drop (Creed et al. 1992) and the rate of photosynthesis is reduced. Survey methods for assessing a weevil population include both qualitative and quantitative observations. Qualitative observations include the presence of weevils and weevil-induced damage, the overall health and density of EWM, and composition of the native plant community. Quantitative data include weevil population density and EWM density. Milfoil density is determined by random collection of stems in a quadrat and converting this to the number of stems per square meter (stems/ m 2 ). Weevil population density (number of weevils per stem) is determined through lab analysis by identifying weevil life stages contained on EWM stems sampled along three transect lines at each site. II Weevil Stocking In June of 2010 EnviroScience biologists stocked 46,000 weevils between three sites located in Rollin Township in the southern portion of Devils Lake. No significant beds of milfoil were found to the north in Woodstock Township. The dominant milfoil in this area was a native species, Variable-leaf milfoil (Myriophyllum heterophyllum), III Weevil Population Survey On July 27, 2011 EnviroScience conducted a weevil population survey in three sites in Devils Lake. Of the three stocking sites from 2010, Site 3 (S3) was the only location where sufficient densities of EWM were available to survey. Additional survey sites (S1 and S2) were established near previous stocking sites. Zebra mussels were observed at all sites DARROW ROAD, STOW, OHIO / TOLL FREE: /

32 " E x c e l l e n c e i n E c o l o g i c a l M o n i t o r i n g " The following is a summary of survey activities in 2011: S1 Site 1 (S1) is located in the southeastern corner of Devils Lake near the Devils Lake Yacht Club. EWM density at S1 was the highest of the sites surveyed in 2011 and composed approximately 25% of the plant community. Native aquatic plant species identified at this site included Clasping-leaf pondweed (Potamogeton perfoliatus) and Large-leaf pondweed (P. amplifolius). No weevil life stages or weevil-induced damage were observed during the survey. Laboratory analysis of EWM samples revealed minimal damage and no visible life stages (Table 1). S2 Site 2 (S2) is located north of S1 near a large sand bar. EWM density at S2 was moderate ( stems/m 2 ) and composed 40% of the plant community. Native aquatic plant species identified at this site included Bladderwort (Utricularia vulgaris), Clasping-leaf pondweed, Coontail (Ceratophyllum demersum), Elodea (Elodea canadensis), Large-leaf pondweed (P. amplifolius), and Northern watermilfoil (Myriophyllum sibiricum). Most noteworthy is the extent of Variableleaf watermilfoil (M. heterophyllum) present in S2. No weevil life stages or weevil-induced damage were observed during the survey. Laboratory analysis of EWM samples revealed minimal damage and no visible life stages (Table 1). S3 (2010 Stocking Site) Site 3 (S3) is located in southwestern portion of the lake, east of the DNR boat access. EWM density at S3 was relatively sparse (16.67 stems/m 2 ) and composed approximately 20% of the plant community. Native aquatic plant species identified at this site included Bladderwort, Chara (Chara sp.), Claspingleaf pondweed, Curly leaf pondweed (Potamogeton crispus), Eel grass/water celery (Valisneria americana), Variable-leaf watermilfoil, and White water lily (Nymphaea sp.). Laboratory analysis revealed damage to 22% of EWM samples and two weevil life stages (Table 1). IV. Discussion Devils Lake maintains the adequate requirements and shoreline habitat to sustain a returning population of milfoil weevils as demonstrated in the 2011 survey. Weevil density has increased in S3 where stocking occurred in 2010 (Figure 1). The weevil population at this site has reached approximately 20% of what the scientific literature indicates is a critical density ( 0.5 weevils/stem) to suppress and cause a decline in EWM (Newman and Biesboer 2000). Weevils have not been augmented in the past at S1 or S2 and these sites currently contain minimal EWM damage indicative of a smaller population DARROW ROAD, STOW, OHIO / TOLL FREE: /

33 " E x c e l l e n c e i n E c o l o g i c a l M o n i t o r i n g " As indicated in Table 1, EWM densities are higher at both non-stocking sites. Contributing factors to less dense EWM at S3 may include both the augmented weevil population and suction harvesting activities in Additional data collection would result in more accurate projections for effectiveness of the weevil population at S3. Devils Lake contains a hybrid milfoil, which closely resembles Eurasian watermilfoil and often requires genetic testing for positive identification. Savin Lake Services collected eighteen stems that were analyzed by the Annis Water Resources Institute in July of Ten of seventeen stems analyzed were hybrid milfoil and the remainders were Eurasian and Variable watermilfoils. Additional sampling in August near the Yacht Club and Boat Launch were identified as Eurasian watermilfoil. Genetic sampling has confirmed the presence of Variable, Eurasian, and hybrid milfoils throughout the lake, but further sampling would more accurately clarify the relative abundance of each species. In 2010, EnviroScience surveyed sites and stocked weevils where EWM was found, but it is possible that some areas contained a hybrid strain. Hybrid milfoil is acceptable habitat for weevils and is more susceptible to weevil herbivory than native milfoil species (Roley and Newman 2006). Variable watermilfoil is the dominant species in the northern portion of the lake and is becoming increasingly dominant in the southern half. Unlike the hybrid strain, positive identification of this species is easier due to distinct differences in the plant structure (Figure 1). Although Variable watermilfoil is considered a native plant species in Michigan, it can grow to a nuisance level and has been observed to fluctuate seasonally. The weevil is not a successful management option for this type of milfoil as differences in the plant structure may interfere with the insect s life cycle. V. Future Recommendations It is the recommendation of EnviroScience, Inc. that the weevil population continue to be augmented in Devils Lake in 2012 as part of a comprehensive milfoil management program. EnviroScience s Milfoil Solution is designed to achieve natural, long-term control of lake-wide milfoil infestations and is able to be integrated with various lake management strategies. The weevil is effective at managing EWM and hybrid milfoil, but management for Variable watermilfoil will need to be addressed should this species become a nuisance. Distinguishing the relative amounts of the three types of milfoil in Devils Lake is a necessary step in determining the types of management strategies to be used in Should you have any questions or comments, please do not hesitate to contact EnviroScience, Inc. at (800) or at slomske@enviroscienceinc.com DARROW ROAD, STOW, OHIO / TOLL FREE: /

34 " E x c e l l e n c e i n E c o l o g i c a l M o n i t o r i n g " Literature Cited: Creed, R.P., Sheldon, S.P., and Cheek, D.M The Effect of Herbivore Feeding on the Buoyancy of Eurasian Watermilfoil. J. Aquat. Plant Manage. 30: Newman, R.M. and Biesboer, D.D A Decline of Eurasian Watermilfoil in Minnesota Associated with the Milfoil Weevil Euhrychiopsis lecontei J. Aquat. Plant Manage. 38: Roley, S.S. and Newman, R. M Developmental Performance of the Milfoil Weevil, Euhrychiopsis lecontei (Coleoptera: Curculionidae), on Northern Watermilfoil, Eurasian Watermilfoil, and Hybrid (Northern x Eurasian) Watermilfoil. Environ. Entomol. 35(1): Table 1. EWM Density (stems/m 2 ) and Weevil Population Analysis (weevils/stem) in Devils Lake Survey Date 6/16/2010 7/27/11 Parameter Measured S1 S2 S3 EWM Density (stems/m 2 ) Total weevils Total stems Avg. weevils/stem Avg. meristems/stem EWM Density (stems/m 2 ) Total weevils Total stems Avg. weevils/stem Avg. meristems/stem ** EWM densities not included in 2010 survey *** These sites were not stocked in 2010 *** *** ** Figure 1. Eurasian watermilfoil (Myriophyllum spicatum) and Variable-leaf 3781 DARROW ROAD, STOW, OHIO / TOLL FREE: /

35 " E x c e l l e n c e i n E c o l o g i c a l M o n i t o r i n g " watermilfoil (Myriophyllum heterophyllum) Eurasian watermilfoil (Myriophyllum spicatum) Variable-leaf watermilfoil (Myriophyllum heterophyllum) 3781 DARROW ROAD, STOW, OHIO / TOLL FREE: /

36 S3 S2 S1 Devils Lake Lenawee County Michigan 2011 Survey Locations

37 Jan. 9 Devils Lake Annual Report Appendix II Naturally, LLC. Suction Harvesting Report

38 Naturally D.A.S.H. & Dredge LLC. Suction Harvesting of Devils Lake was completed for the 2011 season. With over 75,000 sq. ft. of Eurasian Water Milfoil (EWM) removed in over 1200 bags in 40 plus locations. The smallest areas removed were 3 ft. X 3 ft., the largest area was 90 ft. X 75 ft. with the average size being 42 ft. X 42 ft. The depth of water was from 4 ft. to 20 ft. with the 6 ft. to 12 ft. being by far the majority of the locations. I would like to thank Russ Elder of Elder s Nursery & Tree Transplanting Service for furnishing us a site for disposal of the EWM. Russ can testify to the large compost pile of EWM. Rollin Township Trusty Ray McGrath can verify the pickup truck loads of empty bags that went to the land fill.

39 N 3000 feet W SAVIN E 8 7 S Suction Harvest 1 Devils Lake Sections 26, 27, 34 & 35 Woodstock Township and Sections 2, 3, 4, & 10 Rollin Township Lenawee County Suction Harvest Woodstock Township $20, Rollin Township $25, Suction Harvest Suction Hasrvest 3088 Hottis Road, Hale, MI Phone: Fax:

40 Devils Lake Annual Report Appendix III Dr. Ryan Thum - Genetic Testing Results

41 Dr. Ryan Thum dialog and results: "Hi Luke, The hybrids are very closely related to Eurasian watermilfoil because they have roughly half of their genome that comes from Eurasian watermilfoil. Our best estimate of their exact relationship is that they are F1 hybrids between Eurasian and northern watermilfoil. Being a scientist, I have to say there are some caveats to our estimation of whether individuals are F1s, F2s, backcrosses, etc. I would be happy to explain those over the phone, but it is not worth trying to get into over . Cheers, Ryan"