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ASSESSMENT OF THE MILFOIL WEEVIL (EUHRYCHIOPSIS LECONTEI) FOR BIOLOGICAL CONTROL OF EURASIAN WATERMILFOIL (MYRIOPHYLLUM SPICATUM) IN DEVILS LAKE (LENAWEE COUNTY, MI) December, 2010 ASSESSMENT OF THE MILFOIL WEEVIL (EUHRYCHIOPSIS LECONTEI) FOR BIOLOGICAL CONTROL OF EURASIAN WATERMILFOIL (MYRIOPHYLLUM SPICATUM) IN DEVILS LAKE (LENAWEE COUNTY, MI) December, 2010 Prepared for: Mr. Charles Jarrett, Supervisor Woodstock Township 730 Manitou Road Manitou Beach, MI 49253 Mr. John Jenkins, Supervisor Rollin Township 730 Manitou Road Manitou Beach, Michigan 49253 Prepared by: Lakeshore Environmental, Inc. 803 Verhoeks Road Grand Haven, Michigan 49417 TABLE OF CONTENTS SECTION PAGE LIST OF FIGURES....................................................................................................................................... i LIST OF TABLES ....................................................................................................................................... ii LIST OF APPENDICES ............................................................................................................................. iii 1.0 EXECUTIVE SUMMARY ............................................................................................................ 6 2.0 DEVILS LAKE AQUATIC VEGETATION COMMUNITIES ................................................... 8 2.1 3.0 The GPS Point-Intercept Method ....................................................................................... 9 THE PROBLEM: EURASIAN WATERMILFOIL (EWM) ....................................................... 12 3.1 Methods for Control of EWM .......................................................................................... 15 3.1.1 Biological Control ................................................................................................... 15 3.1.2 Aquatic Herbicides and Algaecides ........................................................................ 17 3.1.3 Benthic Barriers ....................................................................................................... 18 3.1.4 Suction Harvesting .................................................................................................. 18 4.0 EVALUATION OF WEEVILS IN DEVILS LAKE (2010) ....................................................... 19 4.1 In Situ Methods................................................................................................................. 19 4.1.1 Weevil Stocking Site Selection ............................................................................... 19 4.1.2 Weevil Stocking ...................................................................................................... 21 4.1.3 Milfoil Stem Collection ........................................................................................... 22 4.1.4 Milfoil Stem Density Assessment ........................................................................... 22 4.2 Laboratory Methods and Analyses................................................................................... 22 4.2.1 Rinsing and Separation of EWM Stems ................................................................. 23 4.2.2 Measurement of EWM Stem Parameters................................................................ 23 4.2.3 Analysis of EWM Stems for Weevil Damage ........................................................ 23 5.0 DEVILS LAKE 2010 WEEVIL DATA ....................................................................................... 24 5.1 6.0 Results and Discussion by Site......................................................................................... 24 DEVILS LAKE 2010 WATER QUALITY DATA ..................................................................... 26 6.1 Results and Discussion by Site......................................................................................... 27 7.0 FUTURE WEEVIL STOCKING RECOMMENDATIONS AND COST ESTIMATES .......... 34 8.0 LITERATURE CITED ................................................................................................................. 36 FIGURES NAME PAGE Figure 1. Variable-Leaved Pondweed................................................................................................. 12 Figure 2. Eurasian Watermilfoil Plant ................................................................................................ 13 Figure 3. Eurasian Watermilfoil Canopy ............................................................................................ 14 Figure 4. Native Milfoil Beds ............................................................................................................. 14 Figure 5. Milfoil Weevil (Euhrychiopsis lecontei) ............................................................................. 16 Figure 6. Aerial Photo of Devils Lake 2010 Weevil Stocking Sites ................................................... 21 Figure 7. Degree of Weevil Damage on EWM Stems among Sites ................................................... 25 Figure 8. EWM Stem Density for All Sites ........................................................................................ 26 TABLES NAME PAGE Table 1. Devils Lake Exotic Aquatic Plants (2010).............................................................................. 8 Table 2. Devils Lake Native Aquatic Plants (2010) ........................................................................... 10 Table 3. Data Table of Weevil Stocking Sites (2010) ........................................................................ 25 Table 4. MDNRE Lake Trophic Status Parameters ............................................................................ 27 Table 5. Devils Lake Spring 2010 Water Quality Data ...................................................................... 33 Table 6. Devils Lake Late Summer 2010 Water Quality Data ........................................................... 33 Table 7. Devils Lake Weevil Program Budget for 2011..................................................................... 34 APPENDICES NAME PAGE APPENDIX A. Devils Lake GPS Grid Data 2010 ............................................................................. 39 Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 6 ASSESSMENT OF THE MILFOIL WEEVIL (EUHRYCHIOPSIS LECONTEI) FOR BIOLOGICAL CONTROL OF EURASIAN WATERMILFOIL (MYRIOPHYLLUM SPICATUM) IN DEVILS LAKE (LENAWEE COUNTY, MI) December, 2010 1.0 EXECUTIVE SUMMARY This report evaluates Eurasian Watermilfoil stem and weevil data collected during the late summer of 2010 in an effort to determine the efficacy of the weevil (Euhrychiopsis lecontei) on Eurasian Watermilfoil (Myriophyllum spicatum) growth characteristics within Devils Lake, Lenawee County, Michigan in sections 26, 27, 34, and 35 of Woodstock Township (T. 5S, R. 1E) and sections 2,3,4,9 and 10 of Rollin Township (T. 6S, R1E). Devils Lake was previously surveyed in July of 2007 and determined to be infested with approximately 2 acres of M. spicatum that was concentrated around the littoral zone of the lake. An additional survey during June of 2009, detected approximately 154.6 acres of Eurasian Watermilfoil. During that survey, it was also determined that approximately 81.8 acres of Eurasian Watermilfoil was present in Woodstock Township and 72.8 acres of Eurasian Watermilfoil was present in the Rollin Township portions of the lake. Recent surveys conducted during late spring of 2010 determined that the Eurasian Watermilfoil population in the Woodstock Township portion of the lake was out-competed by a sudden overgrowth of the native milfoil species, Myriophyllum heterophyllum (Variable Watermilfoil) which grows in very dense beds, yet does not exhibit the fragmentation risk of the Eurasian Watermilfoil species. As a result of this discovery, the stocking of the weevils was recommended to occur in areas of the lake which contained a highly robust population of Eurasian Watermilfoil (Myriophyllum spicatum) to ascertain a high probability of successful colonization by the weevil and resultant healthy population. The areas of Devils Lake which contained robust Eurasian Watermilfoil beds included an area near the south portion of the lake and in an area offshore from the public access site as well as near the lake outlet at the north section. Approximately 41,500 weevil units were applied to the three treatment sites (SE1, W1 and Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 7 W2) located at the southeast and west areas of the lake. The weevil stocking density used for these sites was greater than 200 weevils m-2, which was recommended by Newman and Biesboer (2000) for optimal weevil damage. Data on Eurasian Watermilfoil stem characteristics and weevil damage was collected at the treatment sites during October of 2010. It is suspected that Devils Lake contains a significantly lower population of hybridized milfoil, especially in the Rollin Township section of the lake. In all areas, the clear visual distinction between the native and exotic milfoil species can be made. This may indicate that hybridization of exotic milfoil with M. heterophyllum is less likely than that of M. sibiricum (Northern Watermilfoil). The majority of the native milfoil populations in Devils Lake consist of M. heterophyllum (Variable Watermilfoil). The highest densities of Eurasian Watermilfoil (over 118 stems per square meter) were located in the area offshore from the public access site (Site W1). Stem densities which ranged from 89-110 stems m-2 were noted at the SE1 and W2 sites, respectively. A collection of approximately 40 Eurasian Watermilfoil stems from the 3 total stocking sites has confirmed that the weevil populations are thriving at all stocked locations as indicated by weevil damage, especially at the NW1 site. The majority of the Eurasian Watermilfoil in Devils Lake exists in water with adequate depth to avoid fragmentation from boat propellers. There is some concern, however, that Eurasian Watermilfoil fragments produced from high wave action are spreading to areas outside of the weevil stocking zones and are thus in the process of more Eurasian Watermilfoil bed formations. In areas with these characteristics, it may be advantageous to spot-treat the Eurasian Watermilfoil with registered aquatic herbicides or suction harvesting to prevent further spread. Vulnerable areas generally include near docks and shorelines. The long-term benefits from the weevil may take years to be fully realized because the feeding action of the weevil on the Eurasian Watermilfoil stems requires adequate time for the structural integrity of the stems to decline and eventually result in stem mortality. Water quality data collected from Devils Lake during the spring and summer of 2010 indicates that the lake is meso-eutrophic (moderate in nutrients and high in transparency), and contains an abundance of planktonic green algal species. During the summer, the dissolved oxygen concentration of the lake drops below the recommended concentration of 5.0 mg L-1 which makes the Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 8 hypolimnion (bottom depths of the lake) uninhabitable to fish. This reduction in dissolved oxygen is a normal phenomenon in lakes since the demand for oxygen at the lake bottom is high due to the respiration by microbes which are actively breaking down organic matter. 2.0 DEVILS LAKE 2010 AQUATIC VEGETATION COMMUNITIES The aquatic plant sampling methods used for lake surveys of macrophyte communities commonly consist of shoreline surveys, visual abundance surveys, transect surveys, Aquatic Vegetation Assessment Site (AVAS) Surveys, and GPS Point-Intercept Grid surveys. Other less common and more costly surveys that involve bioacoustic monitoring and/or side-scan sonar imaging are used to determine biomass density in very large bodies of water (i.e. Chesapeake Bay, US). The Michigan Department of Natural Resources and Environment (MDNRE) protocol consists of an Aquatic Vegetation Assessment Site (AVAS) Survey which assigns a percentage of cover to each sampled quadrat based on visual estimates (Table 1), whereas the U.S. Army Corps of Engineers utilizes a GPS Point-Intercept Grid survey for inland lakes following large-scale lake improvement treatments to assess the changes in aquatic vegetation structure and to record the relative abundance and locations of native aquatic plant species. Due to the shallow mean depth and large size of Devils Lake, a bi-seasonal GPS Point-Intercept Grid survey is preferred to assess all aquatic species. MDNRE Species Abundance Meaning % Coverage of AVAS Abundance Code Interpretation Surface Area a Found <2 b Sparse 2 - 20 c Common 21 – 60 d Dense > 60 Table 1. MDNRE AVAS species relative abundance codes used in AVAS surveys Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 9 2.1 The GPS Point-Intercept Grid Survey Method While the MDNRE AVAS protocol considers sampling vegetation using visual observations in areas around the littoral zone, the Point-Intercept Grid Survey method (Appendix A) is meant to assess vegetation throughout the entire surface area of a lake (Madsen et al. 1994; 1996). This method involves conducting measurements at Global Positioning Systems (GPS)-defined locations that have been pre-selected on the computer to avoid sampling bias. Furthermore, the GPS points are equally spaced on a map. The points should be placed together as closely and feasibly as possible to obtain adequate information of the aquatic vegetation communities throughout the entire lake. At each GPS grid point location, two rake tosses are conducted and the aquatic vegetation species and abundance are recorded. In between the GPS points, any additional species and their relative abundance are also recorded using visual techniques. This is especially important to add to the GPS Point-Intercept survey method, since M. spicatum and other invasive plants may be present between GPS points but not necessarily at the pre-selected GPS points. Once the aquatic vegetation communities throughout the lake have been recorded using the GPS points, the data can be placed into a Geographic Information System (GIS) software package to create maps showing the distribution of a particular species. The GPS Point-Intercept method is particularly useful for monitoring aquatic vegetation communities through time and for identification of nuisance species that could potentially spread to other previously uninhabited areas of the lake. For this particular survey, a total of 630 GPS grid points were sampled throughout Devils Lake. This number of grid points was selected to dramatically increase the sample size necessary to reduce variability among lake sampling sites and to yield an accurate estimate of M. spicatum acreage. A table of all aquatic plant species observed in Devils Lake is shown below in Table 2. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 10 Aquatic Aquatic Macrophyte Aquatic Macrophyte Macrophyte Common Name Growth Form Species % of Quadrats Present (of 630) Myriophyllum spicatum,1 Eurasian Watermilfoil Submersed 31.0 Potamogeton crispus,2 Curly-leaf Pondweed Submersed 1.3 Chara vulgaris (macroalga), 3 Muskgrass Submersed 23.0 Potamogeton pectinatus,4 Thin-leaf Pondweed Submersed 5.4 Potamogeton zosteriformis, 5 Flat-stem Pondweed Submersed 3.5 Potamogeton gramineus,7 Variable-leaf Pondweed Submersed 23.2 Potamogeton richardsonii, 9 Clasping-leaf Pondweed Submersed 13.2 Potamogeton illinoensis,10 Illinois Pondweed Submersed 3.8 Vallisneria americana,15 Wild Celery Submersed 3.7 Myriophyllum sibiricum, 17 Northern Watermilfoil Submersed 1.7 Myriophyllum heterophyllum,18 Variable Watermilfoil Submersed 2.9 Ceratophyllum demersum, 20 Coontail Submersed; Non-rooted 1.1 Elodea canadensis, 21 Common Waterweed Submersed 4.1 Utricularia vulgaris, 22 Common Bladderwort Submersed; Non-rooted 0.2 Utricularia minor,23 Small Bladderwort Submersed;Non-rooted 1.6 Najas guadalpensis, 25 Southern Naiad Submersed 4.1 Potamogeton pusillus ,26 Small-leaf Pondweed Submersed;Rooted 9.4 Nymphaea sp., 30 White Waterlily Floating-leaved 2.5 Nuphar sp., 31 Yellow Waterlily Floating-leaved 0.8 Arrow arum, 36 Arrowhead Emergent 2.7 Pontedaria cordata, 37 Pickerelweed Emergent 0.5 Typha sp.,39 Cattails Emergent 0.3 Decodon verticillata, 42 Swamp Loosestrife Emergent 5.4 Lythrum salicaria, 43 Purple Loosestrife Emergent 1.9 Table 2. Aquatic plant species and their relative abundance in Devils Lake (October, 2010). Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 11 The grid survey determined that approximately 41.3% of the surveyed areas (i.e. littoral zone area) were unvegetated and contained bare sand and/or marl. The presence of bare areas was more apparent in 2010 than in 2009 and the reasons are unclear. During the 2010 survey, a total of 15 native submersed, 2 floating-leaved, and 4 emergent aquatic plant species were found for a total of 21 species. The most dominant native aquatic plant species within Devils Lake were in the Potamogetonaceae family, which included the Pondweeds such as Variable-leaf Pondweed (P. gramineus; Figure 1). Chara vulgaris was present in 23.0% of the grid points sampled and thus was the most dominant rooted native submersed aquatic plant (actually a macroalga) in the littoral zone. Chara vulgaris often carpeted the lake bottom in areas where it grew and formed a thick layer which makes it difficult for newly formed M. spicatum fragments to take root in the lake bottom sediment. Thus, preservation of this and other low-growing species are critical for the long-term control of M. spicatum and other nuisance species that spread through fragmentation. Clasping-Leaf Pondweed occupied approximately 13.2% of the littoral zone, which represents a significant increase in this plant from 2009. The pondweeds serve as excellent cover for fish and macroinvertebrates and should be preserved to the extent possible to support a healthy fishery. The majority of the native aquatic plant species in Devils Lake were sparse in abundance and do not currently threaten the balance of the ecosystem or the safety of recreationalists on the lake. In fact, protection of these native aquatic plant species is critical for the ecological balance of Devils Lake. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 12 Figure 1. Variable-Leaf Pondweed (P. gramineus), a common native pondweed present in Devils Lake. 3.0 THE PROBLEM: EURASIAN WATERMILFOIL Eurasian Watermilfoil (Myriophyllum spicatum; Figure 2) is an exotic aquatic macrophyte first documented in the United States in the 1880’s (Reed 1997), although other reports (Couch and Nelson 1985) suggest it was first found in the 1940’s. M. spicatum has since spread to thousands of inland lakes in various states through the use of boats and trailers, waterfowl, seed dispersal, and intentional introduction for fish habitat. M. spicatum is a major threat to the ecological balance of an aquatic ecosystem through causation of significant declines in favorable native vegetation communities within lakes (Madsen et al. 1991; Boylen et al. 1999), and may limit light from reaching native plant species (Newroth 1985; Aiken et al. 1979; Figure 3). Additionally, M. spicatum can alter the macroinvertebrate populations associated with particular native plants of certain structural architecture (Newroth 1985). Within the past decade, research has been conducted on the genotype of hybrid watermilfoil species (Moody and Les, 2002; 2007) which are commonly a result of cross- Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 13 pollination between M. spicatum and other native species such as Northern Watermilfoil (M. sibiricum), and Whorled Watermilfoil (M. heterophyllum). The majority of native milfoils do not form dense canopies, but may instead form dense beds that reach near the surface of the lake (Figure 4). Since the introduction of Eurasian Watermilfoil, many nuisance aquatic plant management techniques such as chemical herbicides, mechanical harvesting, and biological control have been implemented. Thus, biological control may be a preferred method to that is chemical-free and targetspecific, and will not cause fragmentation of M. spicatum. Alternative strategies are discussed in more detail in section 2 below. Figure 2. The submersed exotic aquatic macrophyte, Eurasian Watermilfoil, Myriophyllum spicatum, L. © Superior Photique, 2008 Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 14 Figure 3. A dense canopy of Eurasian Watermilfoil which reduces light availability to favorable native aquatic plant species. Figure 4. Native Watermilfoil species, (above) can also grow in thick beds, but tend not to canopy across the lake surface. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 15 3.1 Methods of Control for Eurasian Watermilfoil The management of exotic aquatic plants is necessary in nutrient-enriched aquatic ecosystems due to accelerated growth and distribution. Management options should be environmentally and ecologically sound and financially feasible. Options for control of exotic aquatic plants are limited yet are capable of achieving strong results when used properly. Implementation of a management program which protects native aquatic plants (especially the submersed pondweeds and the macroalga Chara) in Devils Lake to continue to provide for a healthier fishery is recommended. However, exotic aquatic plant species should be managed with solutions that will yield long-term results and with minimum harm to the aquatic environment. 3.1.1 Biological Control The use of the aquatic weevil, Euhrychiopsis lecontei to control M. spicatum has become a popular option for many inland lakes. The weevil naturally exists in many of our lakes; however, the lack of adequate populations in many lakes requires that they be implanted or stocked for successful control of the Eurasian Watermilfoil. The weevil feeds almost entirely on M. spicatum and will leave native aquatic species unharmed. The weevil burrows into the stems of the Eurasian Watermilfoil and removes the vascular tissue, thereby reducing the plant’s ability to store carbohydrates (Newman et al. 1996). Eventually, the Eurasian Watermilfoil stems lose buoyancy and the plant decomposes on the lake bottom. Recent research has shown that the weevils require a substantial amount of aquatic plant biomass for successful control of M. spicatum. In addition, the weevils require adequate over-wintering habitat since they over-winter within shoreline vegetation. Lakes with sparse Eurasian Watermilfoil distribution and abundant metal and concrete seawalls are not ideal candidates for the milfoil weevil. Although there is heavy developmental density around the Devils Lake shoreline, an abundance of metal seawalls, and heavy boat traffic, there is adequate overwintering vegetation around the Devils Lake shoreline. Late-summer (October, 2010) surveys of Devils Lake revealed favorable Eurasian Watermilfoil stem densities (89-118 stems m-2) to support a sustainable weevil population. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 16 The native weevil, Euhrychiopsis lecontei (Coleoptera: Curculionidae; Figure 5) has been shown to cause detrimental impacts on the exotic aquatic macrophyte M. spicatum (Creed et al. 1992, Creed and Sheldon 1995, Newman et al. 1996). The weevil life cycle consists of larval, pupae, and adult life stages, which all are involved in the destruction of the Eurasian Watermilfoil plants. Completion of a single life cycle generally occurs in 17-30 days and is dependent upon water temperature (Newman et al., 1997). In the initial stages of biological control, larvae are applied to the apical (top) portions of stems and destroy the vascular tissue (Creed and Sheldon 1993, 1994a, Newman et al. 1996), which significantly hinders stem elongation. During the pupation stage, stem vascular tissue is further destroyed during the construction of the pupal chamber (Creed and Sheldon 1993). During the adult phase, mature weevils feed on the Eurasian Watermilfoil leaves and stems (Creed and Sheldon 1993). Figure 5. The milfoil weevil, Euhrychiopsis lecontei, Enviroscience, Inc., used with permission. Observed impacts include the devascularization of stem tissue which causes buoyancy loss (due to a loss of stored CO2 gases in stem epithelial cells) and photosynthetic growth inhibition of Eurasian Watermilfoil plants (Creed et al. 1992; Newman et al. 1996). Cofrancesco et al. (2004) summarized Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 17 that the primary mode of weevil damage to the stem includes inhibition of stem elongation. The weevil is a native herbivore to the waters of the north temperate region, and will feed on native milfoil populations if the invasive milfoil is not present, though it prefers the invasive milfoil over native species. Other herbivore species such as Phytobius leucogaster and Acentria ephemerella showed negligible results in the reduction of Eurasian Watermilfoil (Sheldon 1995; Creed and Sheldon 1994). It is possible that many water physical, chemical, and biological variables could affect the success of the E. lecontei control method. As a result, weevil evaluation treatments should minimize variables to the extent possible. In situ evaluations have the advantage of eliminating manipulation effects (a form of variable reduction) of transferring plants from a field site to the laboratory or mesocosm. Conversely, many field evaluations are scrutinized by the presence of multiple variables that can vary considerably in the field and confound experimental results. Some studies have assessed the impacts of the weevil on Eurasian Watermilfoil biomass (Scribailo and Alix, 2003); however this method is more amenable to reviewing long-term impacts of the weevil on Eurasian Watermilfoil growth. In the past, the Devils Lake Yacht Club (DLYC) and Lakes Preservation League (LPL) requested an evaluation to estimate an effective weevil density given the observed Eurasian Watermilfoil growth within Devils Lake. During 2010, public hearings were held to gain a measure of support from the public. As a result of the demonstrated support, Rollin and Woodstock Townships has been working with Lakeshore Environmental, Inc. to assess the efficacy of the weevils as more are added to the Devils Lake ecosystem. 3.1.2 Aquatic Herbicides and Algaecides The use of aquatic chemical herbicides is regulated by the MDNRE under Part 33 (Aquatic Nuisance) of the Natural Resources and Environmental Protection Act, P.A. 451 of 1994, and requires a permit from the Michigan Department of Natural Resources and Environment (MDNRE). The permit contains a list of approved herbicides for a particular body of water, as well as dosage rates, treatment areas, and water use restrictions. Furthermore, residents that reside within 100 feet of the proposed treatment area must be notified at least seven days, but not more than forty-five days prior to the initial treatment date. A certified herbicide applicator usually notices the residents in advance of the proposed treatment date, and Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 18 during the day of treatment. Contact and systemic aquatic herbicides are the two primary herbicide types used in aquatic systems. Contact herbicides cause damage to leaf and stem structures; whereas systemic herbicides are assimilated by the plant roots and are lethal to the entire plant. Wherever possible, it is preferred to use a systemic herbicide for longer-lasting aquatic plant control. There are often restrictions with usage of some systemic herbicides around shoreline areas that contain shallow drinking wells. Systemic herbicides such as Triclopyr (Trade Name: Renovate OTF®) could be used to successfully treat localized or widely dispersed beds of Eurasian Watermilfoil. The current infestation of Devils Lake could be spot-treated with systemic herbicides such as Triclopyr as an alternative to 2,4D for selective long-term control, with little negative impacts to the native aquatic vegetation communities within the lake. 3.1.3 Benthic Barriers and Weed Rollers Benthic barriers or mats are generally placed onto the lake bottom of beach areas in early spring after ice-off to prevent the germination of various aquatic plants, including Eurasian Watermilfoil. The barriers generally come in sizes which are practical only for small areas (i.e. 12’x12’). If used after the aquatic vegetation has grown, they will generally require a month for the underlying vegetation to decay (Madsen 1997). In addition, the mats generally require a use permit from the MDNRE prior to installation. For more information on the mats and where to order them, visit the website: http://www.lakemat.com. 3.1.4 Suction Harvesting (Diver Assisted) Diver-assisted suction harvesting is a labor-intensive method where individual aquatic plants are hand-pulled from the sediment by a SCUBA diver and fed into a large suction tube which offloads the suctioned vegetation onto a barge where they are bagged in biodegradable bags and disposed of properly. Although this method is time-consuming, it has the benefit of being chemical-free and is very selective in the vegetation that is removed based on the selectivity of the diver. As long as the bottom of the lake is not disrupted, the benthic communities are usually unharmed. This strategy has Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 19 been used on both Devils and Round Lakes in 2010 and may be used again to control sparse Eurasian Watermilfoil populations from spreading outside of weevil stocking areas and near docks and beaches. 4.0 AN EVALUATION OF WEEVILS IN DEVILS LAKE, LENAWEE CO, MI During the summer of 2010, approximately 41,500 weevil units were placed into the southeast and west sections of Devils Lake. Efforts were made to assure that weevil density studies followed recommendations by (Newman and Biesboer, 2000), with current weevil stocking densities of ≥ 200 weevils m-2. 4.1 4.1.1 In Situ Methods Weevil Stocking Site Selection Devils Lake is a 1,337-acre lake located in sections 26, 27, 34, and 35 of Woodstock Township (T. 5S, R. 1E) and sections 2,3,4,9 and 10 of Rollin Township (T. 6S, R1E), in Lenawee County, Michigan. The lake has an approximate maximum depth of 63 feet and a mean depth of 14.2 feet. Although the majority of the lake is deep, there is approximately 350 acres of surface area that is capable of being colonized by M. spicatum. Nutrient data such as total phosphorus may help to explain nuisance native aquatic vegetation growth; however, the growth of invasive species such as M. spicatum is less dependent upon nutrient increases and more dependent on the mode of introduction and propagation. A review of recent vegetation survey data (October, 2010) by Lakeshore Environmental, Inc., revealed that the amount of Eurasian Watermilfoil in the littoral zone areas had increased from 17% to 30% since the 2009 survey. This could be attributed to growth of the Eurasian Watermilfoil beds prior to weevil implementation. Monitoring of these beds will be critical in the determination of the weevil efficacy. The majority of this milfoil was present in the proposed stocking sites. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 20 Devils Lake West Shore and Southeast Shore Sites The first stocking site (Site W2) was selected at a water depth of approximately 1.5 meters due to the presence of large, dense healthy M. spicatum beds, and the favorable site protection characteristics which included large emergent vegetation beds that may serve as overwintering vegetation sites. The second stocking site (Site W1, out from the public access site) was selected at a water depth of 2-3 meters and had an abundance of thick milfoil beds with a mean stem density of 118 stems m-2. The third site (Site SE 1) was also selected since other dense areas of milfoil were located there in approximately 1.5 meters of water depth. Surveys conducted in July of 2010 demonstrated that the native milfoil species had dominated the northern portion of the lake and the Eurasian Watermilfoil was sparse in most areas north of the Woodstock township line. As a result, it was recommended to stock all weevils in places where Eurasian Watermilfoil was dominant and the stem densities were great enough to sustain viable weevil populations. All of the stocking sites are shown in Figure 6. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 21 W2 W1 SE1 Figure 6. West and Southeast Shore Weevil Stocking Sites in Devils Lake, Lenawee County, MI. 4.1.2 Weevil Stocking Milfoil weevils were stocked on June 16 of 2010 in three areas near the west (W1, W2) and southeast (SE1) shores of Devils Lake. Stocking areas were determined through a combination of previous Point-Intercept aquatic vegetation surveys conducted during fall of 2009 and spring of 2010. Approximately 41,500 weevil units were placed among the three sites, with the greatest number of units (> 20,000) placed at Site W1, since this site had the highest Eurasian Watermilfoil stem density. All new treatment sites were marked with a GPS unit for future reference in the field. In each of the Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 22 lake treatment areas, a lake bottom area of 625 ft2 (58.1 m-2) was delineated to yield a weevil density of ≥ 200 weevil units per m-2. 4.1.3 Milfoil Stem Collection On 22 October, 2010, a total of 120 Eurasian Watermilfoil stems were collected from all of the current (n=3) weevil stocking sites by skin-divers. Individual Eurasian Watermilfoil stems were randomly selected and removed at the sediment-water interface and placed into a labeled 2-gallon ziplock® plastic collection bag for analysis. 4.1.4 Milfoil Stem Density Assessment On 7 July, 2010, three 0.25 m2 PVC quadrat samples were also collected from each of the three new treatment sites (W1, W2, and SE1) to measure the stem density in order to estimate the number of stems per square meter in Devils Lake. The PVC quadrat was placed on the lake bottom and all plants which were within the square were cut and placed into labeled 2-gallon ziplock® plastic bags for stem counts. A total of three for each site were collected and a mean was calculated to yield an average Eurasian Watermilfoil stem density for each weevil treatment (stocking) site. 4.2 Laboratory Methods and Analyses After Eurasian Watermilfoil stems were collected in the field and transported to the laboratory, they were cleaned and sorted prior to being inspected under the dissection microscope. Individual Eurasian Watermilfoil stems were keyed to the species level of taxonomy using an aquatic vegetation taxonomic key (Crow and Hellquist, 2000). Individual methods and analyses are explained in the sections below. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 23 4.2.1 Rinsing and Separation of Eurasian Watermilfoil Stems Each Eurasian Watermilfoil stem that was collected at each of the 3 sampling sites was sorted and untangled prior to analysis under the microscope. In order to avoid washing away any delicate life cycle stages (i.e. newly laid eggs or larvae) off of the exterior of the Eurasian Watermilfoil stems, washing of the stems was conducted only after an initial scan of the Eurasian Watermilfoil stem was completed and any of the associated weevil life cycle stages (if any present) were recorded. Eurasian Watermilfoil stems that could not be immediately analyzed were placed between moistened paper towels which were refrigerated to halt tissue degradation. If necessary, stems with thick encrustations of zebra mussels (Dreissena polymorpha) or other debris were cleaned with deionized water and a steady stream of cold and lightly pressurized water. Whenever possible, tissue analyses occurred as soon as the dissection microscope was available after each sample. 4.2.2 Measurement of Eurasian Watermilfoil Stem Parameters Stem damage parameters such as stem length, stem compression diameter, and number of stem lateral branches was measured and recorded. Stem length was measured in (cm) with the use of a calibrated measuring tape 6 meters in length. Stem compressional diameter was measured in (mm) with the use of a set of calibrated, digital calipers, which was re-calibrated between each reading for enhanced accuracy. Stem lateral branches were counted as additional meristems that were formed off of the main axis of the plant stem. 4.2.3 Analysis of Eurasian Watermilfoil Stems for Weevil Damage The condition of the Eurasian Watermilfoil stems (index of stem damage, Jermalowicz-Jones et al., 2007) was measured on each of the collected stems. The index of stem damage includes a stem tissue damage scale that ranges from 0 to 5. The index ranged from 0 - 5 with a value of “0” denoting no weevil damage visible, a “1” denoting the presence of eggs on an apical meristem, a “2” denoting the presence of larvae or eggs on or in the stem, a “3” indicated the presence of larvae in the stem tissues Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 24 and vascular tissue damage, “4” indicated the presence of larvae or pupae and severe necrosis of the stem tissue, and a “5” denoted both severe tissue necrosis, weevil pupae or larvae, and the loss of foliar leaves. To assess for weevil damage, each individual milfoil stem was placed under the dissection microscope (first under the 10x objective power and then under the 20x objective power) to look at the plant from the apical tip to the roots. Both overhead and base-lighting are used to illuminate the plant specimens and determine if weevil larvae or other life cycle stages are present in or on the individual stems. If weevil stages were located in or on the stems, they were recorded. 5.0 DEVILS LAKE SUMMER 2010 WEEVIL DATA RESULTS The assessment of all weevil stocking sites from 2010 (Table 3) allowed for a measure of the continued efficacy of the weevil on the degradation of milfoil stems and for the determination of future areas to be re-stocked. 5.1 Results and Discussion by Site All of the three sampling sites exhibited some extent of weevil damage; however, Sites SE1 and W1 contained the highest amount of weevil stem damage at 2.8 and 2.5 respectively (Figure 6), which was slightly higher than damage values noted for Round Lake. The weevil damage at Site SE1 1 was marginally significant (p < 0.055) when compared to the other two sites. Site SE1 contained the lowest mean stem diameters but these were not correlated with increased weevil damage. Mean stem length was not significantly different among sites and demonstrated a much more consistent height of plant relative to those stem lengths observed in the Round Lake sites. The differences in stem lengths at all three sites will be evaluated again in 2011 to determine if weevils have caused the decrease in stem lengths as previous research has indicated (Cofranceso et al., 2004; Jermalowicz-Jones et al., 2008). The number of milfoil stem lateral branches was also not significantly different among sites; however, Site W2 had the highest mean number of lateral branches and also the second highest mean stem density. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 25 Stem density (Figure 7) has been shown to be directly correlated with the survival of the weevil which depends on a high abundance of Eurasian Watermilfoil stems for population growth. Site W1 had the highest stem density at 118.0±38.9 stems per m-2, followed by Site W2 with 110.0±42.2 stems per m-2. Site SE1 had the lowest stem density at 89.0±13.8 stems per m-2. Sampling Mean Stem Mean Weevil Site Diameter Mean Stem Mean Stem Mean # Lateral Damage Index Length (cm) Density Branches (mm) (0-5) (# stems m-2) Site W1 2.3±0.4 2.5±1.8 147.2±32.7 118.0±38.9 0.9±1.1 Site W2 2.2±0.5 2.3±1.7 148.3±31.4 110.0±42.2 1.1±1.7 Site SE1 2.1±0.3 2.8±1.6 142.7±34.5 89.0±13.8 1.1±1.0 Table 3. Summary Data Table of All Weevil Stocking Sites (2010). Numbers are means and standard deviations of n=40 stems collected at each of the 3 sites. Mean Index of Damage to EWM Stems 3 2.8 2.5 2.3 2 1 0 SITE SE1 SITE W1 SITE W2 Figure 7. Degree of weevil damage (via the weevil damage index) on milfoil stems among sites within Devils Lake, Lenawee County, Michigan (based on October, 2010 samples). Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 26 Mean Stem Density per Site 140 120 100 80 60 40 20 0 118 110 89 SITE SE1 SITE W1 SITE W2 Figure 8. M. spicatum stem density (based on July, 2010 samples) for each weevil stocking site within Devils Lake, Lenawee County, Michigan. 6.0 DEVILS LAKE WATER QUALITY DATA RESULTS Water quality parameters such as water temperature, dissolved oxygen, total phosphorus, total Kjeldahl nitrogen, alkalinity, pH, conductivity, among others, appear to not be directly correlated with weevil abundance within lakes (Jester et al., 2000). However, these metrics were measured in May and October of 2010 and are compared to the baseline values (Table 4). Devils Lake is considered mesotrophic based on high water clarity (mean Secchi transparency = 22.5), moderate nutrient levels at depths beyond 30 feet, and an abundance of aquatic plant growth. The south-central Deep basin 1 was selected as the major deep basin which was representative of the overall lake health. The quality of water is highly variable among Michigan inland lakes, although some characteristics are common among particular lake classification types. The water quality of Devils Lake is affected by both land use practices and climatic events. Climatic factors (i.e. spring runoff, heavy rainfall) may alter water quality in the short term; whereas, anthropogenic (man-induced) factors (i.e. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 27 shoreline development, lawn fertilizer use) alter water quality over longer time periods. Furthermore, lake water quality helps to determine the classification of particular lakes. Lakes that are high in nutrients (such as phosphorus and nitrogen) and chlorophyll-a, and low in transparency are classified as eutrophic; whereas those that are low in nutrients and chlorophyll-a, and high in transparency are classified as oligotrophic. Lakes that fall in between these two categories are classified as mesotrophic. Devils Lake is classified as meso-eutrophic based on its moderate transparency and high nutrient concentrations. Lake Trophic Status Total Phosphorus -1 Chlorophyll-a -1 Secchi Transparency (µg L ) (µg L ) (feet) Oligotrophic < 10.0 < 2.2 > 15.0 Mesotrophic 10.0 – 20.0 2.2 – 6.0 7.5 – 15.0 Eutrophic > 20.0 > 6.0 < 7.5 Table 4. Lake Trophic Status Classification Table (MDNRE) 6.1 Devils Lake Water Quality Parameters Water quality parameters such as dissolved oxygen, water temperature, conductivity, turbidity, total dissolved solids, pH, total alkalinity, total phosphorus, total Kjeldahl nitrogen, and Secchi transparency, among others, all respond to changes in water quality and consequently serve as indicators of water quality change. These parameters are discussed below along with water quality data specific to Devils Lake (Tables 5 and 6). Water quality data was collected on May 31, 2010 and October 12, 2010 over the south-central deep basin in Devils Lake. Dissolved Oxygen Dissolved oxygen is a measure of the amount of oxygen that exists in the water column. In general, dissolved oxygen levels should be greater than 5 mg L-1 to sustain a healthy warm-water fishery. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 28 Dissolved oxygen concentrations in Devils Lake may decline if there is a high biochemical oxygen demand (BOD) where organismal consumption of oxygen is high due to respiration. Dissolved oxygen is generally higher in colder waters. Dissolved oxygen is measured in milligrams per liter (mg L-1) with the use of a dissolved oxygen meter and/or through the use of Winkler titration methods. The dissolved oxygen concentrations in Devils Lake were normal and consistent with increased depth during the May sampling event and ranged between 7.9-9.8 mg L-1. During summer months, dissolved oxygen at the surface is generally higher due to the exchange of oxygen from the atmosphere with the lake surface, whereas dissolved oxygen is lower at the lake bottom due to decreased contact with the atmosphere and increased biochemical oxygen demand (BOD) from microbial activity. A decline in dissolved oxygen beyond 30 feet during the October sampling (just before turnover) from 8.8 at the surface to 0.9 at the bottom may cause increased release rates of phosphorus (P) from Devils Lake bottom sediments which may lead to more algal growth over time. Water Temperature The water temperature of lakes varies within and among seasons and is nearly uniform with depth under winter ice cover because lake mixing is reduced when waters are not exposed to wind. When the upper layers of water begin to warm in the spring after ice-off, the colder, dense layers remain at the bottom. This process results in a “thermocline” that acts as a transition layer between warmer and colder water layers. During the fall season, the upper layers begin to cool and become denser than the warmer layers, causing an inversion known as “fall turnover”. In general, lakes with deep basins will stratify and experience turnover cycles. Water temperature is measured in degrees Celsius (ºC) or degrees Fahrenheit (ºF) with the use of a submersible thermometer. The May water temperatures of Devils Lake demonstrated nearly isothermic conditions between the surface and bottom. Late summer water temperatures ranged between 67ºF at the surface and 44.7 ºF at the lake bottom. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 29 Conductivity Conductivity is a measure of the amount of mineral ions present in the water, especially those of salts and other dissolved inorganic substances. Conductivity generally increases as the amount of dissolved minerals and salts in a lake increases, and also increases as water temperature increases. Conductivity is measured in microsiemens per centimeter (µS cm -1) with the use of a conductivity probe and meter. Conductivity values for Devils Lake were low and consistent among sampling sites and similar to most healthy inland lakes in Michigan. Conductivity ranged between 335 µS cm-1 and 360 µS cm-1 for spring and late summer water samples. Baseline parameter data such as conductivity are important to measure the possible influences of land use activities (i.e. road salt influences) on Devils Lake over a long period of time, or to trace the origin of a substance to the lake in an effort to reduce pollutant loading. Turbidity Turbidity is a measure of the loss of water transparency due to the presence of suspended particles. The turbidity of water increases as the number of total suspended particles increases. Turbidity may be caused from erosion inputs, phytoplankton blooms, stormwater discharge, urban runoff, resuspension of bottom sediments, and by large bottom-feeding fish such as carp. Particles suspended in the water column absorb heat from the sun and raise the water temperature. Since higher water temperatures generally hold less oxygen, shallow turbid waters are usually lower in dissolved oxygen. Turbidity is measured in Nephelometric Turbidity Units (NTU’s) with the use of a turbimeter. The World Health Organization (WHO) requires that drinking water be less than 5 NTU’s; however, recreational waters may be significantly higher than that. The turbidity of Devils Lake was low and ranged from 0.2 – 1.7 NTU’s during the sampling events. The lake bottom is predominately sandy/marl substrate with some silt, which increases the turbidity values near the lake bottom. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 30 pH The pH is a measure of acidity or basicity of water. The standard pH scale ranges from 0 (acidic) to 14 (alkaline), with neutral values around 7. Most Michigan lakes have pH values that range from 6.5 to 9.5. Acidic lakes (pH < 7) are rare in Michigan and are most sensitive to inputs of acidic substances due to a low acid neutralizing capacity (ANC). pH is measured with a pH electrode and pH-meter in Standard Units (S.U). The pH of Devils Lake water ranged from 7.6 – 8.0 during the late spring and late summer sampling. It is not uncommon for lakes in the northern region of Michigan to possess pH values slightly lower than those of southern lakes due to the underlying geological features which help determine pH. From a limnological perspective, Devils Lake is considered “slightly basic” on the pH scale. Total Alkalinity Total alkalinity is the measure of the pH-buffering capacity of lake water. Lakes with high alkalinity (> 150 mg L-1 of CaCO3) are able to tolerate larger acid inputs with less change in water column pH. Many Michigan lakes contain high concentrations of CaCO3 and are categorized as having “hard” water. Total alkalinity is measured in milligrams per liter of CaCO 3 through an acid titration method. The total alkalinity of Devils Lake is considered above average (> 150 mg L-1 of CaCO3), and indicates that the water is slightly alkaline. Total alkalinity ranged from 173-188 mg L-1 of CaCO3 during the spring and late summer sampling. Total alkalinity may change on a daily basis due to the re-suspension of sedimentary deposits in the water and respond to seasonal changes due to the cyclic turnover of the lake water. Total Phosphorus Total phosphorus (TP) is a measure of the amount of phosphorus (P) present in the water column. Phosphorus is the primary nutrient necessary for abundant algae and aquatic plant growth. Lakes which contain greater than 20 µg L-1 of TP are defined as eutrophic or nutrient-enriched. TP Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 31 concentrations are usually higher at increased depths due to higher release rates of P from lake sediments under low oxygen (anoxic) conditions. Phosphorus may also be released from sediments as pH increases. Total phosphorus is measured in micrograms per liter (µg L-1) with the use of a chemical autoanalyzer. Mean surface total phosphorus (TP) concentrations for the Devils Lake Deep Basin sampling site during spring were < 0.020 mg L-1. Total phosphorus concentrations at the bottom depths averaged < 0.025 mg L-1. Total Kjeldahl Nitrogen Total Kjeldahl Nitrogen (TKN) is the sum of nitrate (NO3-), nitrite (NO2-), ammonia (NH4+), and organic nitrogen forms in freshwater systems. Much nitrogen (amino acids and proteins) also comprises the bulk of living organisms in an aquatic ecosystem. Nitrogen originates from atmospheric inputs (i.e. burning of fossil fuels), wastewater sources from developed areas (i.e. runoff from fertilized lawns), agricultural lands, septic systems, and from waterfowl droppings. It also enters lakes through groundwater or surface drainage, drainage from marshes and wetlands, or from precipitation (Wetzel, 2001). In lakes with an abundance of nitrogen (N: P > 15), phosphorus may be the limiting nutrient for phytoplankton and aquatic macrophyte growth. Alternatively, in lakes with low nitrogen concentrations (and relatively high phosphorus), the blue-green algae populations may increase due to the ability to fix nitrogen gas from atmospheric inputs. Lakes with a mean TKN value of 0.66 mg L-1 may be classified as oligotrophic, those with a mean TKN value of 0.75 mg L-1 may be classified as mesotrophic, and those with a mean TKN value greater than 1.88 mg L -1 may be classified as eutrophic. Devils Lake contained highly variable values for TKN (= 0.50 – 1.00 mg L1 ). Secchi Transparency Secchi transparency is a measure of the clarity or transparency of lake water, and is measured with the use of an 8-inch diameter standardized Secchi disk. Secchi disk transparency is measured in feet (ft) or meters (m) by lowering the disk over the shaded side of a boat around noon and taking the Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 32 mean of the measurements of disappearance and reappearance of the disk. Elevated Secchi transparency readings allow for more aquatic plant and algae growth. Eutrophic systems generally have Secchi disk transparency measurements less than 7.5 feet due to turbidity caused by excessive planktonic algae growth. The Secchi transparency of Devils Lake averaged 18.5 feet during the 2010 sampling period. This transparency is adequate to allow abundant growth of algae and aquatic plants in the majority of the littoral zone of the lake. Secchi transparency is variable and depends on the amount of suspended particles in the water (often due to windy conditions of lake water mixing) and the amount of sunlight present at the time of measurement. Total Suspended and Dissolved Solids Total Suspended Solids (TSS) is the measure of the amount of suspended particles in the water column. Particles suspended in the water column absorb heat from the sun and raise the water temperature. Total suspended solids is often measured in mg L-1 and analyzed in the laboratory. The lake bottom contains many fine sediment particles which are easily perturbed from winds and wave turbulence. Spring values would likely be higher due to increased watershed inputs from spring runoff and/or increased planktonic algal communities. In addition, Total Dissolved Solids (TDS) is a measure of the amount of inorganic and organic solids dissolved in the lake water that may cause a stained color or increase conductivity. The concentration of TSS in Devils Lake during the spring and late summer sampling events ranged from < 2.0 mg L-1 to < 15.0 mg L-1. Total dissolved solids averaged between 20.2 mg L-1 and 43.1 mg L-1. The acceptable standard for drinking water is 100 mg L-1. Oxidative Reduction Potential The oxidation-reduction potential (Eh) of lake water describes the effectiveness of certain atoms to serve as potential oxidizers and indicates the degree of reductants present within the water. In general, the Eh level (measured in millivolts) decreases in anoxic (low oxygen) waters. Low E h values are therefore indicative of reducing environments where sulfates (if present in the lake water) Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 33 may be reduced to hydrogen sulfide (H2S). Decomposition by microorganisms in the hypolimnion may also cause the Eh value to decline with depth during periods of thermal stratification. The E h (ORP) values for Devils Lake ranged between 142.3 mV and 32.1 mV from the surface to the bottom within the lake, and thus were within a normal range for meso-eutrophic lakes. Depth ft Water Temp DO mg L pH -1 S.U. Cond. µS cm -1 Turb. ORP Total Total Total Phos. NTU mV Kjeldahl Alk. mg L-1 Nitrogen mgL-1 mg L-1 CaCO3 ºF 0 55.6 9.8 7.5 360 0.2 142.3 < 0.50 182 <0.020 30 48.9 8.1 7.9 354 0.2 89.5 < 0.50 157 <0.020 60 43.5 7.9 7.6 335 0.9 32.1 <0.50 173 <0.020 Table 5. Devils Lake Water Quality Parameter Data Collected over Deep Basin 1 on May 31, 2010. Depth ft Water Temp DO mg L pH -1 S.U. Cond. µS cm -1 Turb. ORP Total Total Total Phos. NTU mV Kjeldahl Alk. mg L-1 Nitrogen mgL-1 mg L-1 CaCO3 ºF 0 67.0 8.8 8.0 354 0.5 113.8 < 0.50 188 < 0.020 30 52.8 4.9 7.9 347 0.8 77.4 < 0.50 176 < 0.020 60 44.7 0.9 7.7 340 1.7 49.5 <1.00 162 <0.025 Table 6. 2010. Devils Lake Water Quality Parameter Data Collected over Deep Basin 1 on October 12, Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 34 7.0 FUTURE WEEVIL STOCKING RECOMMENDATIONS AND COST ESTIMATES The weevil stocking density used during 2010 was estimated to be > 200 weevils per square meter (m-2), and has been found to be adequate for weevil stem damage. Based on the 2010 seasonal data, it is recommended that approximately 5,000 weevil units should be placed into each of the three sites during the late spring or early summer of 2011. After the stocking has taken place, stem parameters similar to those collected in 2010 should be collected again at all previously stocked sites to assess the efficacy of the weevils. Parameters such as milfoil stem density, weevil counts per stem, and declines in stem length should be measured and proposed cost estimates of the 2011 aquatic vegetation management program are shown below in Table 7. In addition, regular whole-lake point-intercept aquatic vegetation surveys should be conducted to determine locations of any new milfoil infestations throughout Devils Lake and to monitor the distribution and abundance of the native aquatic plant species. Small colonies of Eurasian Watermilfoil should be removed with suction harvesting or aquatic herbicides. Recent 2010 data for aquatic plant species in Devils Lake can be found in APPENDIX A. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 35 Proposed 2011 Management Improvement Item Estimated 2011 Cost Biological Control (Weevils @$1.20 per unit) 15,000 units $18,000 Suction Harvesting or Herbicides (approx. 10 acres@$490 per acre); permits Professional Limnologist Services (Limnologist surveys/Scientific Annual $5,700 $14,000 Reports/ WQ Monitoring, Vegetation mapping, Contractor oversight, Riparian Education); Includes printing and mailing of newsletter (Costs for professional services will be equally divided among the two townships) Contingency TOTAL ANNUAL ESTIMATED COST $3,770 $42,470 Table 7. Proposed Devils Lake Eurasian Watermilfoil Management Budget for 2011. Note: It is recommended that the total cost of the program be divided equally among each township. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 36 8.0 LITERATURE CITED Aiken, S.G., P.R. Newroth, and I. Wile. 1979. The biology of Canadian weeds. 34. Myriophyllum spicatum L. Can. J. Plant Sci. 59: 201-215. Boylen, C.W., Lawrence, W.E., and Madsen, J.D. 1999. Loss of native aquatic plant species in a community dominated by Eurasian Watermilfoil. Hydrobiologia 415: 207-211. Cofrancesco, A.F., McFarland, D.G., Madsen, J.D., Poovey, A.G., and Jones, H.L. 2004. Impacts of Euhrychiopsis lecontei (Dietz) from different populations on the growth and nutrition of Eurasian Watermilfoil. ERDC/TN APCRP-BC-07. Couch, R., and E. Nelson 1985. Myriophyllum spicatum in North America. Pp. 8-18. In: Proc. First Int. Symp. On watermilfoil (Myriophyllum spicatum) and related Haloragaceae species. July 23-24, 1985. Vancouver, BC, Canada. Aquatic Plant Management Society, Inc. Creed, R. P., Jr., S.P. Sheldon, and D. M. Cheek. 1992. The effect of herbivore feeding on the buoyancy of Eurasian milfoil. J. Aquat. Plant. Manage. 30:75-76. Creed, R. P., and S.P. Sheldon. 1994. The effect of two herbivorous insect larvae an Eurasian watermilfoil. J. Aquat. Plant Manage. 32: 21-26. Creed, R.P., Jr., and S.P. Sheldon. 1995. Weevils and watermilfoil: did a North American herbivore cause the decline of an exotic plant? Ecol. Appl. 5: 1113-1121. Creed, R. P., Jr. 2000. The Weevil-Watermilfoil Interaction at Different Spatial Scales: What We Know and What We Need To Know. J. Aquat. Plant Manage. 38: 78-81. Jester, L.L., Bozek, M.A., Helsel, D.R., and Sheldon, S.P. 2000. Euhrychiopsis lecontei distribution, abundance, and experimental augmentations for Eurasian Watermilfoil control in Wisconsin lakes. . J. Aquat. Plant Manage. 38: 88-97. Madsen, J.D., J.W. Sutherland, J.A. Bloomfield, L.W. Eichler, and C.W. Boylen. 1991. The decline of native vegetation under dense Eurasian watermilfoil canopies. J. Aquat. Plant Manage. 29: 94-99. Madsen, J.D. G.O. Dick, D. Honnell, J. Schearer, and R.M. Smart. 1994. Ecological assessment of Kirk Pond, Miscellaneous Paper A-94-1, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 37 Madsen, J.D., J.A. Bloomfield, J.W. Sutherland, L.W. Eichler, and C.W. Boylen. 1996. The aquatic macrophyte community of Onondaga Lake: Field survey and plant growth bioassays of lake sediments, Lake and Reservoir Management 12, 73-79. Madsen, J.D. 1999. Point intercept and line intercept methods for aquatic plant management. Aquatic Plant Control Technical Note MI-02, February 1999. Newman, R. M., K.L. Holmberg, D. D. Biesboer, and B.G. Penner. 1996. Effects of a potential biocontrol agent, Euhrychiopsis lecontei, on Eurasian milfoil in experimental tanks. Aquat. Bot. 53: 131-150. Newman, R.M., Borman, M.E., and Castro, S.W. 1997. Developmental performance of the weevil Euhrychiopsis lecontei on native and exotic watermilfoil host plants. J. North Amer. Benthol. Soc. 16:627-634. Newman, R. M., and D. D. Biesboer, 2000. A decline of Eurasian Watermilfoil in Minnesota associated with the Milfoil Weevil, Euhrychiopsis lecontei. . J. Aquat. Plant Manage. 38: 105-111. Newroth, P.R. 1985. A review of Eurasian water milfoil impacts and management in British Columbia. Pp. 139-153. In: Proc. First Int. Symp. On watermilfoil (Myriophyllum spicatum) and related Haloragaceae species. July 23-24, 1985. Vancouver, BC, Canada. Aquatic Plant Management Society, Inc. Parsons, J.K., and R.A. Matthews. 1995. Analysis of the associations between macroinvertebrates and macrophytes in a freshwater pond. Northwest Science, 69: 265-275. Parsons, J.K., K.S. Hamel, J.D. Madsen, and K.D. Getsinger. 1999. The Use of 2,4-D for Selective Control of an Early Infestation of Eurasian Watermilfoil in Loon Lake, Washington. J. Aquat. Plant Manage. 39: 117-125. Reed, C.F. 1977. History and disturbance of Eurasian milfoil in United States and Canada. Phytologia 36: 417-436. Roley, S.S., and Newman, R. M. 2006. Developmental performance of the milfoil weevil, Euhrychiopsis lecontei (Coleoptera: Curculionidae), on northern watermilfoil, Eurasian watermilfoil, and hybrid (northern x Eurasian) watermilfoil. Environ. Entomol, 35: 121-126. Scribailo, R.W., and M.S. Alix. 2003. Final Report on the Weevil Release Study for Indiana Lakes. Lake and River Enhancement Program, Indiana. 12 pp. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 38 Sheldon, S.P. 1995. The potential for biological control of Eurasian milfoil (Myriophyllum spicatum) 1990-1995. Final Report. Department of Biology, Middlebury College, Middlebury, VT. Sheldon, S.P., R.P. Creed, Jr. 1995. Use of a native insect as a biological control for an introduced weed. Ecol. Appl. 5: 1122-1132. Sutter, T.J., and R.M. Newman 1997. Is predation by sunfish (Lepomis spp.) an important source of mortality for the Eurasian milfoil biocontrol agent Euhrychiopsis lecontei? J. Freshw. Ecol. 12: 225-234. Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 39 APPENDIX A DEVILS LAKE AQUATIC VEGETATION DATA BY GPS LOCATION (OCTOBER, 2010) Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 40 GPS Sample Quadrat Macrophyte Species and Abundance Present 711 1c,5b,6b,3b,7b 712 1d,5b,7b,6a,3b 713 3b 714 None 715 1a,31b,5b,21b 716 3b,7a 717 1d,11b,9b,7b,3a 718 None 719 None 720 None 721 39b,31b,7b,3a 722 3b,5b 723 1d,11a,9b,6a,5b,3c 724 1d,9b,26b,7b,10a 725 1d,21a,5b,23b,7b 726 1d,11a,9b,26c,7b 727 1d,11b,21b,9a,6c,7b,3a 728 1c,21a,11a,9a,26c,3b,7b 729 1c,11a,9b 730 1d,11a,21a,9a,3b,10b 731 1d,11a,21b,6b,9b,3b 732 1d,3b 733 1d,11b,6a,7b 734 1d,9a,6c,26c,7b,3b 735 1c,10b,6b,7b,3b Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 41 GPS Sample Quadrat Macrophyte Species and Abundance Present 736 1d,9a,8a,21b,23a,6b 737 1d,9a,8a,21a,6b 738 1d,8a,21a,6b 739 1c,21a,15a,6b,26b 740 None 741 31b 742 31a 743 None 744 1d,8a,6a,26b 745 1d,23a,8a,21a,5a,6b 746 1d 747 1d,8b,6b 748 1d,8b 749 1d,8a,6a 750 1d,8a,6a,26b 751 1d,8b,5a,6b 752 1c,5b,8a,6c,26b 753 1d,8a,6c,26b 754 1c,8a,5a,21a,6c,26b 755 1b,8a,5a,26c,6c 756 1d,8a,6c,26b 757 1d,8a6b,26b 758 1d,8a,21a,6b,26b 759 1d,8a,6b 760 None 761 1c,8a,11a,21a,6b 762 1d,8a,11a,21a,6b Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 42 GPS Sample Quadrat Macrophyte Species and Abundance Present 763 1d,8b,6b,7b,18b 764 4b,3b,7b,6a 765 1d,26b,9b,7a,3b 766 1b,26b,9b,3a 767 3a 768 39b, 3a,7a 769 39c,3b,7b,9a 770 1d,21b,6b,7a 771 1d,3b 772 1d,3b,8a,7b 773 3b,7a 774 1d,8a 775 1c,8a 776 1b,8b,3b,4a 777 1c,4b,3a 778 15b,4b,10a,7b 779 7b,6a,9b,4b,3b 780 6b,3b,7a 781 6a,9b,7b,3a 782 6b,10b,7a,8a 783 1b,7b,3b 784 1c 785 1c,8b,9a,7c,3b,11b 786 1c,8a,26c 787 1a,26b,3b 788 15b,7b Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 43 GPS Sample Quadrat Macrophyte Species and Abundance Present 789 1d,21a,8a,6b 790 3a 791 1d,9a,6b 792 1d,8a,6a 793 21b,8a 794 1c 795 39d (shore) 796 8a,9a,21a 797 1d,8a,21a,6b 798 1d,8a,21a,6b 799 1d,8a,9a,21a,6b 800 None 801 1d,6a 802 1a,9c 803 1b,9a,8a,6b 804 9a,8b,1a 805 1a,8a,6b 806 8a,1c 807 1d,8a 808 1c,8a,5a 809 1d 810 1d,8a,9a,6b 811 1c,8a,9a,6c 812 1d,5a,8a,9a,21a,20a,6c 813 1b,8a,9a,21a,6b 814 8a,9a,21a Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 44 GPS Sample Quadrat Macrophyte Species and Abundance Present 815 1d,7b,9b 816 3b 817 3a,7a 818 1a 819 1c,3c,7b 820 9b,7b,11a,10a 821 6b,9a,26a 822 5b,26b,6b 823 1a,5b,7a 824 None 825 39a,3b,7b 826 39a,7b 827 3a 828 1c,21a,26c,6b,9b,7b 829 1c,7c,3b 830 1c,7b,10b,9a 831 1a,9c,8a,6c,26b 832 1a,9c,26b 833 1c,3b 834 1b,3c,7b,26b 835 3c 836 3a,7a 837 1d,8b,9b,7c 838 3c 839 7a 840 26a Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 45 GPS Sample Quadrat Macrophyte Species and Abundance Present 841 3c,7b,21b 842 9b,3b,7a 843 7b 844 None 845 None 846 None 847 1c,7b,9a 848 1d,9c,7a,3b 849 1b,9b,11a,26a 850 1c,15b,9b,6b,3a 851 4a 852 39a 853 39a 854 3a 855 1c,8a,6b,26c 856 1a,6c,26b,23a 857 1b,7c,3b 858 1d,7a,9b 859 1c,9a,7b,3a 860 3a 861 None 862 None 863 1d,9b,6b,26a 864 1c,9a,26b 865 3b,26a 866 7c,26a Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 46 GPS Sample Quadrat Macrophyte Species and Abundance Present 867 None 868 None 869 None 870 1d,6c,7b,3b 871 1d,26b,9b,7a,3b 872 23a,26b,3b 873 4b,7b 874 15b,3c,7b 875 9b,8a,7b,3b 876 3a,15b 877 3b,7a 878 1b,3b,7a 879 6a 880 1a 881 1a,7a 882 3b 883 None 884 None 885 39a,3c,7b 886 None 887 None 888 None 889 None 890 None 891 None 892 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 47 GPS Sample Quadrat Macrophyte Species and Abundance Present 893 3c 894 1b,3c,7b,18b 895 1b,18b,7b 896 1c,18a,3b,7b 897 None 898 None 899 8d,7b,3b,9a 900 None 901 None 902 None 903 1c,7b,9b,3b,26a 904 1d 905 1a,10b,26b 906 None 907 1a,3b,7b 908 3b 909 3b,7a,6b 910 1d,9b,3b,7b 911 1a 912 None 913 None 914 None 915 None 916 None 917 None 918 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 48 GPS Sample Quadrat Macrophyte Species and Abundance Present 919 None 920 None 921 None 922 None 923 None 924 None 925 None 926 None 927 None 928 7b,3b,9a 929 7a 930 3a 931 None 932 None 933 None 934 6b,26a,7b,9b,3a 935 1b,4b,6a 936 7b,10a,4b 937 3a 938 None 939 None 940 None 941 None 942 None 943 None 944 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 49 GPS Sample Quadrat Macrophyte Species and Abundance Present 945 None 946 1a,26b,7a 947 None 948 None 949 None 950 1c,9b,26b 951 1d, 26c,8b,7b,3b 952 1c,8b,39a,26b 953 3b,7b,9a 954 1c,7b,10a 955 1a,9b,10a 956 3b 957 None 958 None 959 1b,7b,8a 960 3b,7b 961 None 962 None 963 None 964 None 965 None 966 6b,8b,1a,4b 967 1b,7b,6a 968 7b,6b,9b,3a 969 1b,8a,10a,4b,6c 970 4b,7a,9b,1a Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 50 GPS Sample Quadrat Macrophyte Species and Abundance Present 971 None 972 1c,9b,26a,3b,7b 973 3a 974 3a 975 1c,9a,8b,4b,7a 976 None 977 None 978 None 979 10b,7a,9a 980 None 981 None 982 None 983 None 984 None 985 None 986 None 987 None 988 None 989 8b,3a 990 1c,6a,7b,10a 991 1b,8b,9a 992 1b,7b 993 3a 994 None 995 1c,3b 996 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 51 GPS Sample Quadrat Macrophyte Species and Abundance Present 997 None 998 39b,3b,7a 999 39b,7b 1000 None 1001 None 1002 None 1003 None 1004 None 1005 None 1006 None 1007 None 1008 None 1009 None 1010 None 1011 None 1012 None 1013 None 1014 None 1015 None 1016 None 1017 None 1018 None 1019 1d,6b,9b,21b,26b 1020 1d,18b,7b,4b,20a 1021 1b,4b,7v,18b,9b 1022 39a,3a Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 52 GPS Sample Quadrat Macrophyte Species and Abundance Present 1023 1d,9b,6a,7b 1024 1c,3b 1025 3b 1026 None 1027 None 1028 None 1029 None 1030 None 1031 None 1032 None 1033 None 1034 None 1035 None 1036 None 1037 None 1038 None 1039 None 1040 None 1041 None 1042 23b,26b,7b,3b,4a,10a 1043 3b 1044 3a 1045 39a,3b,7a 1046 39a,26a 1047 None 1048 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 53 GPS Sample Quadrat Macrophyte Species and Abundance Present 1049 3b,7b 1050 3b,7b 1051 None 1052 7a 1053 3a 1054 3b,7a 1055 None 1056 None 1057 None 1058 None 1059 None 1060 None 1061 None 1062 None 1063 21a,5a 1064 3b,20a,8a 1065 3a,4b,7a 1066 3b,7b,9a 1067 1d,26b,23a,4b,3a 1068 1d,3b,7a,9b,20a 1069 3b 1070 None 1071 None 1072 None 1073 1c,26b,7b,9b,15a 1074 1c,15a,26a,7a,3a Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 54 GPS Sample Quadrat Macrophyte Species and Abundance Present 1075 3b 1076 4b 1077 3a,7a 1078 None 1079 None 1080 None 1081 None 1082 None 1083 None 1084 None 1085 None 1086 None 1087 None 1088 None 1089 None 1090 3a,8a 1091 None 1092 None 1093 None 1094 None 1095 39a,3b,7a 1096 39a,3b 1097 3a 1098 None 1099 None 1100 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 55 GPS Sample Quadrat Macrophyte Species and Abundance Present 1101 4b,7a 1102 3a,4a 1103 7a 1104 7a 1105 None 1106 39a, 3a 1107 39a 1108 3b 1109 None 1110 None 1112 None 1113 None 1114 None 1115 39a, 7a 1116 39b 1117 None 1118 None 1119 None 1120 None 1121 None 1122 None 1123 None 1124 None 1125 None 1126 39a,7b,3a 1127 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 56 GPS Sample Quadrat Macrophyte Species and Abundance Present 1128 3b 1129 39a, 3b 1130 3b,7a 1131 7b 1132 3a 1133 None 1134 None 1135 None 1136 39b,3a 1137 39b,7a 1138 39b 1139 None 1140 None 1141 None 1142 None 1143 1b,8b,9a,6b,26a,15a 1144 1b,6b 1145 1b,5a,9b,7b 1146 3a 1147 None 1148 None 1149 1c,6b,9b,5a,15a,4b,7b 1150 1d,26b,10a,9b,7c 1151 3a 1152 None 1153 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 57 GPS Sample Quadrat Macrophyte Species and Abundance Present 1154 1a 1155 1b,9b,26b,15a,20b,4b,7a,25b 1156 1d,5b 1157 None 1158 10a 1159 None 1160 10b,6b,4a,25b 1161 8b,4a,7a 1162 None 1163 None 1164 None 1165 None 1166 None 1167 None 1168 3a 1169 8a,3a,9a 1170 7b,3a 1171 None 1172 None 1173 None 1174 1b,7b 1175 1c,21b,8a,6b,26b,25a 1176 1d,5b,9b,18a,21a,6b,26b,25b 1177 1d,5b,15b,18b,6b,26c,25b 1178 1d,6b,18b,26b,25b 1179 39c,7a,3b Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 58 GPS Sample Quadrat Macrophyte Species and Abundance Present 1180 None 1181 None 1182 None 1183 None 1184 1d,7b,3b,9b,15a,18b,26a,23a 1185 4b,7b 1186 None 1187 None 1188 None 1189 None 1190 None 1191 None 1192 39a,4b,7a 1193 39a, 7a 1194 1a,4b,7a 1195 1b,9a,7b 1196 3b 1197 3a,7a 1198 None 1199 None 1200 None 1201 None 1202 1d,9b,26b,23a,15a,18b,5a 1203 1d,6b,9b,7b,3b 1204 1d,9b,6b,3b 1205 1b,3c Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 59 GPS Sample Quadrat Macrophyte Species and Abundance Present 1206 1b,6b,9b,7a 1207 1b,6a,9a,7b 1208 3c,7b 1209 1b,6a,9a,7b 1210 1d,9b,4b 1211 1d,3b,9b,11a,2a 1212 1d,6b,9b,4a 1213 1b 1214 None 1215 None 1216 None 1217 3a 1218 None 1219 1b,26c,4b,7b,9a,2a 1220 1c,23a,15b,26b,7a,2a 1221 3b 1222 3a 1223 1d,26b,9a,7b,3a 1224 1b,3b 1225 1b,3b,6c,4b,26c,2b 1226 1b,6b,26b,2b 1227 1a ,6b,2b 1228 1b,9a, 6b,26b 1229 6b,3b,7b 1230 1a,6b,21a,7b 1231 7b,21a Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 60 GPS Sample Quadrat Macrophyte Species and Abundance Present 1232 1b,7b,3a,6a 1233 1d,6a,7b 1234 1b,7b,9b,15a,20a,22b 1235 1c,23b,26b,3b,7c 1236 7b,6a 1237 3b,7b 1238 1b,6a,3b 1239 1c,9b,3b,7b 1240 1d,5b,6b,15b,26b 1241 1c,5b,15b,18a 1242 1b,9b,6b,26b 1243 1d,9b 1244 None 1245 None 1246 None 1247 None 1248 1a,6b 1249 1b,23a,3b,7a 1250 1d,7b,3a 1251 1b,3b,7b,6b 1252 1b,15a,6b,26b,2c 1253 1a,9b,6a,4b,26a,2c 1254 None 1255 None 1256 None 1257 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 61 GPS Sample Quadrat Macrophyte Species and Abundance Present 1258 None 1259 1b,15a,18b,3b,7a 1260 8a,7b,3a 1261 3b,7b,11a 1262 1d,6b,3b,10a 1263 1b,3a,9b,10a,4b 1264 1b,15a,11a 1265 1b,15b,18b,7a 1266 1c,3a 1267 1a,3b,7a 1268 1b,6b,9a,3b 1269 None 1270 None 1271 None 1272 1c,6b,7a,9a 1273 1a,7a,3b 1274 1b,7b,9a,10a 1275 None 1276 3b,26a,7b,4a 1277 3b,7a 1278 None 1279 None 1280 18b,3c,7a 1281 None 1282 None 1283 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 62 GPS Sample Quadrat Macrophyte Species and Abundance Present 1284 3b,7b 1285 7a 1286 None 1287 39a,4a,7a 1288 7a 1289 None 1290 None 1300 None 1301 None 1302 None 1303 None 1304 None 1305 None 1306 None 1307 None 1308 None 1309 None 1310 None 1311 None 1312 None 1313 None 1314 None 1315 None 1316 None 1317 None 1318 None Lakeshore Environmental, Inc. Devils Lake 2010 Annual Report December, 2010 Page 63 GPS Sample Quadrat Macrophyte Species and Abundance Present 1319 None 1320 3a