December 15, 2017 Ms. Gretchen Schatschneider District Manager Bucks County Conservation District 1456 Ferry Rd # 704 Doylestown, PA 18901 Re: Lake Nockamixon Aquatic Macrophyte Survey Final Report ALI Project No. 1005-23 Dear Ms. Schatschneider and Board Members: Aqua Link was retained by the Bucks County Conservation District to perform an aquatic macrophyte (vascular plant) survey of Lake Nockamixon amid the peak of the 2017 growing season. Lake Nockamixon is a 1,450-acre man made impoundment located in Bucks County, Pennsylvania. The lake was formed by damming the main tributary, Tohickon Creek. Two other tributaries that feed the lake are Three-mile Run Creek and Haycock Creek. The purpose of this survey was to document the species and subsequent densities of both native and non-native aquatic vegetation throughout the lake. This survey is of significant importance due to the documented prevalence of invasive aquatic vegetation, namely Eurasian watermilfoil (Myriophyllum spicatum) and hydrilla (Hydrilla verticillata). The collected data will provide the foundation for further implementation of aquatic plant management strategies. A noted species of Lake Nockamixon, Eurasian watermilfoil (Myriophyllum spicatum) was a focal point of this survey. EWM (Eurasian watermilfoil) is a non-native, highly aggressive aquatic plant that outcompetes more desirable, native plant species. EWM is an extremely well adapted plant and is able to thrive in a wide variety of environmental conditions. This plant grows rooted in water depths from less than 1 to 10 meters (less than 1 to 33 feet), generally reaching the surface in depths up to 5 meters (16 feet). Though adapted to a wide variety of substrate types, Eurasian watermilfoil (EWM) seems to favor fine-textured, inorganic sediments. Branching stems emerge from dense, spreading roots. The leaves are arranged in whorls of 3 to 6 leaves (4 leaves per whorl is common). The whorls are openly spaced along the stem with 1 to 3 cm between nodes. The leaves are finely feather- divided and are typically with 12 to 24 pairs of thread-like leaflets on each leaf. Since the leaves of other milfoil species generally have fewer than 14 leaflet pairs, counting leaflets can provide helpful clues to identifying EWM. Bucks County Conservation District Lake Nockamixon 2017 Aquatic Macrophyte Survey Another documented species of Lake Nockamixon, hydrilla (Hydrilla verticillata), is also a non-native, highly aggressive aquatic plant. Hydrilla is a perennial plant that has the ability to form dense stands and can reach the water’s surface in up to 20 feet of water. The northern strain of hydrilla (present in Pennsylvania) is monecious and therefore has both male and female reproductive organs (i.e. flowers) on the same plant. This plant branches profusely and after reaching the surface via vertical growth and then extends across the water horizontally forming thick surface mats. This document represents the final letter report for the aquatic macrophyte survey as performed by Aqua Link in June 2017. Section 1 of this report discusses our study design, all methods used to collect field data, and how these data were analyzed. Section 2 represents the results of the aquatic plant survey and Section 3 provides a discussion of our conclusions and our recommendations to control nuisance, problematic aquatic vegetation and to further protect the lake in terms of water quality. It should be noted that this report cannot be posted on the Internet or any websites without the written approval of Aqua Link. 1. Study Design, Field Methods & Data Analysis Study Design & Field Methods Aqua Link performed an aquatic macrophyte (aquatic plant) survey of Lake Nockamixon on June 1, 2017. This survey was designed and managed by a NALMS (North American Lake Management Society) Certified Lake Manager (CLM) with extensive experience in performing lake studies and managing aquatic plants. The aquatic plant survey was performed by a 2-man field crew using a 16-ft boat equipped with an outboard motor and Lowrance water depth chart plotter (fathometer or water depth sounder). For this study, aquatic vegetation (floating leaved and submerged) was sampled at seven (7) different locations throughout the lake. These locations focused on those areas where aquatic plants can most easily be introduced to the lake, namely major tributaries to Lake Nockamixon and improved boat launch areas. At each lake location, aquatic plants were sampled at five (5) different sampling points resulting in a total of thirty-five (35) sampling points for the entire aquatic plant survey. 2 Bucks County Conservation District Lake Nockamixon 2017 Aquatic Macrophyte Survey The seven sampling areas for the Lake Nockamixon aquatic plant survey are shown in Figure 1. The areas are as follows; Threemile Run Creek inlet, Threemile Run boat launch, Tohickon Creek inlet, Marina, Tohickon boat launch, Haycock boat launch, and Haycock Creek inlet. In the field, the locations of all sampling points were recorded using a Garmin GPS unit (Montana 680t model). Following field data collection, all GPS coordinates data were downloaded and archived as a digital data file on our corporate server. At each lake sampling point, the aquatic plant community was observed and documented. Aquatic plants at the lake surface in reach of the boat were collected by hand for field identification. Next, submerged aquatic vegetation was sampled using an aquatic rake. The aquatic rake was lowered to the lake bottom and dragged a distance of approximately 1 meter (3.3 feet) on each side of the boat. Collected aquatic plants were sorted in the boat and identified. In addition, Aqua Link recorded the relative densities (low, medium, and high) of all aquatic plants that were collected at each of the sampling locations. Aqua Link also retained representative specimens of all vegetation collected during the macrophyte survey. All retained plant specimens were packaged and transported back to our laboratory. All identification of collected plant specimens were then verified by another Aqua Link professional lake manager. Data Analysis Aqua Link developed an aquatic plant survey database for this project using Microsoft Excel. All aquatic plant data (e.g. plant identifications, relative densities and GPS locations) were entered into the database for analysis. The GPS data for all sampling locations were transferred into Google Earth mapping software in order to develop additional aquatic macrophyte coverage maps for this project. 2. Aquatic Macrophyte Survey Results Aqua Link performed a macrophyte (aquatic plant) survey for Lake Nockamixon on June 1, 2017. The study design, methods, and data analysis for this aquatic macrophyte survey were previously discussed in Section 1. Pictures taken during this aquatic plant survey are presented in Attachment A. All field data collected during as part of this survey are included in Attachment B and Attachment C provides pictures (illustrations) and descriptions of all aquatic plants identified during this aquatic plant survey. The seven (7) major sampling areas for the Lake Nockamixon aquatic plant survey as shown in Figure 1. The locations of the thirty-five (35) individual sampling points are presented in Figures 2-8. For this study, a total of eight (8) different aquatic plant species were identified during the June 2017 aquatic plant survey (Table 1). The plant type for each identified plant is 3 Bucks County Conservation District Lake Nockamixon 2017 Aquatic Macrophyte Survey also provided in Table 1. Plant types were designated as either submerged aquatic vegetation (SAV) floating-leaved aquatic vegetation (FAV), or emergent aquatic vegetation (EAV). Table 2 shows the distribution of non-native, invasive aquatic vegetation by area. Refer to Attachment C for background information on the aquatic plant species that were collected on the field study date. Table 1 Aquatic Plants in Lake Nockamixon in 2017 Common Name Scientific Name Plant Type Curly Leaf Pondweed Potamogeton crispus SAV Water Willow Justicia americana EAV Coontail Ceratophyllum spp. SAV Eurasian Watermilfoil Myriophyllum spicatum SAV Water Primrose Ludwigia spp. SAV Hydrilla Hydrilla verticillata SAV Duckweed Lemna minor FAV White Water Lilly Nymphaea spp. FAV Table 2 Non Native Invasive Plants in Lake Nockamixon in 2017 Curly-leaf Area EWM Hydrilla Pondweed Threemile Run Inlet Low Low Threemile Run Boat Launch High Tohickon Creek Inlet Med Low Marina High Tohickon Boat Launch Med Low Med Haycock Boat Launch High Low Haycock Creek Inlet High Low In addition, Figures 2-8 also show the individual sampling locations where Eurasian watermilfoil (Myriophyllum spicaticum) and hydrilla (Hydrilla verticillata) were observed. Both of these submerged aquatic plants are considered non-native and highly invasive in Pennsylvanian lakes. More information about these aquatic invaders can be found in Attachment C. 4 Figure 1 - Sampling Locations for Lake Nockamixon Aquatic Macrophyte Survey www.aqualinkinc.com Figure 2.1 Sampling Points Figure 2.2 Distribution of EWM Figure 2.3 Distribution of Hydrilla Figure 2 Threemile Run Creek Sampling Locations & Aquatic Plant Distributions Figure 3.1 Sampling Points Figure 3.2 Distribution of EWM Figure 3.3 Distribution of Hydrilla Figure 3 Threemile Run Boat Launch Sampling Locations & Aquatic Plant Distributions Figure 4.1 Sampling Points Figure 4.2 Distribution of EWM Figure 4.3 Distribution of Hydrilla Figure 4 Tohickon Creek Inlet Sampling Locations & Aquatic