2014 Aquatic Invasive Species Surveys of New York City Water Supply Reservoirs Within the Catskill/Delaware and Croton Watersheds

2014 aquatic invasive species surveys of New York City water supply reservoirs within the Catskill/Delaware and Croton Watersheds Megan Wilckens1, Holly Waterfield2 and Willard N. Harman3 INTRODUCTION The New York City Department of Environmental Protection (DEP) oversees the management and protection of the New York City water supply reservoirs, which are split between two major watershed systems, referred to as East of Hudson Watersheds (Figure 1) and Catskill/Delaware Watershed (Figure 2). The DEP is concerned about the presence of aquatic invasive species (AIS) in reservoirs because they can threaten water quality and water supply operations (intake pipes and filtration systems), degrade the aquatic ecosystem found there as well as reduce recreational opportunities for the community. Across the United States, AIS cause around $120 billion per year in environmental damages and other losses (Pimentel et al. 2005). The SUNY Oneonta Biological Field Station was contracted by DEP to conduct AIS surveys on five reservoirs; the Ashokan, Rondout, West Branch, New Croton and Kensico reservoirs. Three of these reservoirs, as well as major tributary streams to all five reservoirs, were surveyed for AIS in 2014. This report details the survey results for the Ashokan, Rondout, and West Branch reservoirs, and Esopus Creek, Rondout Creek, West Branch Croton River, East Branch Croton River and Bear Gutter Creek. The intent of each survey was to determine the presence or absence of the twenty- three AIS on the NYC DEP’s AIS priority list (Table 1). This list was created by a subcommittee of the Invasive Species Working Group based on a water supply risk assessment. This study will help the DEP by notifying them if and where AIS have made it into the reservoirs or their tributaries so they can take the appropriate steps to eradicate them before they become established and cause serious environmental or economic damage. Surveys of the New Croton and Kensico reservoirs are planned for 2015, though in October 2014, Hydrilla was found in the New Croton. Rapid response survey work has been conducted by DEP, BFS, NYS Dept. of Environmental Conservation, among others, and 2015 work plans will be amended as necessary. Concurrent work on the use of environmental DNA (eDNA) to determine AIS presence/absence is underway (Newton 2014). Genus-specific primers based on the DNA of Orconectes rusticus, Corbicula fluminea, Driessena polymorpha, Hydrilla verticillata, Myriophyllum spicatum and Cipangopaludina chinensis will be developed in the hopes that analysis of water samples can yield presence/absence data, reserving time-intensive field surveys for areas where AIS are known to be present. 1BFS Intern, summer 2014. Current Affiliation: Le Moyne College, Syracuse, NY. Supported by NYSDEP contract # CAT-421. 2 CLM. Research Support Specialist. SUNY Oneonta Biological Field Station. 3 CLM. Distinguished Service Professor. Rufus J. Thayer Otsego Lake Research Chair and Director. Figure 1. Map of the East of Hudson Watersheds. The Croton Watershed includes West Branch Reservoir (surveyed in 2014) and Kensico and New Croton Reservoirs (to be sampled in 2015) (From Anonymous 2007a). Figure 2. New York City Department of Environmental Protection’s map of the Catskill/Delaware Watershed (West of Hudson). Two of the sampled reservoirs are located in this watershed: Ashokan and Rondout (From Anonymous 2007b). Invasive Species of Concern, Mechanisms of Spread & Impacts of Establishment Since native species have already filled the niches of a particular ecosystem, invasive species must be “fundamentally different from the resident species,” meaning Theymust have “advantageous properties” that would help them out-compete the native community (Thompson 1991). A successful invasion of a natural community requires dispersal, establishment, and survival (Hobbs 1989). There are several factors that should be taken into account when attempting to see if an invasive species will colonize an area. Propagule pressure (the measure of number of individuals of a species per release event and the number of release events), a new species’ traits as well as the invasibility of the environment all play important roles in the successfulness of an invasive species (Lonsdale 1999). Table 1. New York City Department of Environmental Protection priority aquatic invasive species list. These were the species this survey focused on in the five tributaries and reservoirs. Organism Type Scientific Name Common Name Aquatic Invertebrate Corbicula fluminea Asiatic Clam Aquatic Invertebrate Cipangopaludina chinensis Chinese Mystery Snail Aquatic Invertebrate Bithynia tentaculata Faucet Snail Aquatic Invertebrate Cercopagis pengoi Fish Hook Water Flea Aquatic Invertebrate Cordylophora caspia Freshwater Hydroid Aquatic Invertebrate Potamopyrgus antipodarium New Zealand Mud Snail Aquatic Invertebrate Dreissena bugensis Quagga Mussel Aquatic Invertebrate Orconectes rusticus Rusty Crayfish Aquatic Invertebrate Bythotrephes longimanus Spiny Water Flea Aquatic Invertebrate Dreissena polymorpha Zebra Mussel Aquatic Invertebrate Eriocheir sinensis Chinese Mitten Crab Aquatic Plant Egeria densa Brazilian Waterweed Aquatic Plant Didymosphenia geminata Didymo Aquatic Plant Hydrocharis morsus-ranae L. European Frogbit Aquatic Plant Trapa natans Water Chestnut Aquatic Plant Hydrilla verticillata Hydrilla Aquatic Plant Myriophyllum spicatum Eurasian Watermilfoil Aquatic Plant Myriophyllum aquaticum Parrot’s Feather Aquatic Plant Myriophyllum heterophyllum Variable-leafed Watermilfoil Aquatic Plant Fallopia japonica Japanese Knotweed Aquatic Plant Lythrum salicaria Purple Loosestrife Aquatic Plant Phragmites australis Common Reed Aquatic Plant Potamogeton crispus Curly Leaf Pondweed The invasibility of an environment is largely influenced by anthropogenic activities. Reservoir construction has shaped the face of numerous landscapes around the world and as a result has led to the rapid increase in AIS throughout waterways. Reservoirs are considered “stepping- stones” for the spread of invaders (Havel et al. 2005). As humans construct reservoirs and build dams to fill them, altering the flow of water, they disturb habitats and the native species inhabiting them and therefore allow AIS to fill the resulting empty niches. Invasive species, without natural predators and little competition, are able to establish themselves in the early stages of community succession (Havel et al. 2005). Connections between reservoirs and their tributaries allow AIS to move from one habitat to the next, spreading at rapid rates. Some invasive species pose more of a threat than others and are considered nuisance species. Several AIS on the DEP’s list should be of more concern than others, due either to their threat to the economic attributes of the reservoir or their ecological aspects. Those having more of an economic threat to the reservoirs include Myriophyllum spicatum (Eurasian watermilfoil), Potamogeton crispus (curly leaf pondweed) and Hydrilla verticillata (hydrilla). Myriophyllum spicatum and P. crispus have characteristics that allow them to dominate the water body. These two species have an “ability to rapidly propogate vegetatively, have an opportunistic nature for obtaining nutrients, and enhanced photosynthetic efficiency” (Nichols & Shaw 1986). Hydrilla verticillata also forms dense vegetative mats, spreading through plant fragmentation and turions, and by producing tubers that can remain dormant for several years before sprouting (Balyszak 2013). These traits enable them to overcrowd water bodies (inhibiting boat traffic and impeding fishing activities), and foul water system infrastructure through clogging of water intake pipes and filtration systems resulting in large damage costs. Two AIS that are threats to both the economic and ecological aspects of reservoirs are Trapa natans (water chestnut) and Dreissena polymorpha (zebra mussels). Trapa natans is an aquatic plant that forms extensive, dense beds on the surface of water bodies. This characteristic inhibits boating but it also blocks incoming sunlight to the lower water levels, shading out submerged plants and microscopic species that are important in the natural food web associated with that body of water (Hummel & Kiviat 2004). Dreissena polymorpha spreads rapidly and can cover vast expanses of substrate, including intake pipes and filtration systems, sometimes causing up to $1 billion in maintenance (Connelly et al. 2007). They are filter feeders and that can cause major community changes as energy and nutrients are being directed away from the surrounding benthic invertebrates (Hebert et al. 1989). Several other AIS pose greater threats to the functioning of reservoirs, from Fallopia japonica (Japanese knotweed), Phragmites australis (common reed), Lythrum salicaria (purple loosestrife) to Orconectes rusticus (rusty crayfish). Fallopia japonica spreads vegetatively through rhizomes, creating dense monocultures that crowd out native plant species, diminishing the available habitat native fauna depend on (Forman & Kesseli 2002). Phragmites australis is similar in that it dominates shortgrass communities by forming tall, dense, monotypic stands (Windham & Lathrop 1999) along the shorelines and in shallow waters. It often displaces strands of Typha (cattails) which help remove toxins from water bodies and therefore degrades the water quality of these reservoir systems. Lythrum salicaria is spreading at a rate of 115,000 ha/year (Thompson et al. 1987) and

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