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 is a threat to wetland communities, outcompeting native plant species like Typha and displacing native fauna that depend on the native flora. Orconectes rusticus, on the other hand, is an invertebrate aquatic invasive species. They dominate native crayfish species through competition and hybridization. They also eat more than the native species, ranging from fish eggs to small fish (threatening fish populations), benthic invertebrates, detritus to aquatic plants (which are important for shelter, nesting substrate and erosion control) without which, would cause a variety of problems in the food web (Gunderson 2008).

Due to their rapid spreading capabilities, the DEP has implemented programs and

regulations to try to stop aquatic invasive species from spreading to new, unaffected areas. Since 1992 the DEP has required all recreational boats entering their water bodies to be cleaned with water at 140°F in order to keep aquatic hitchhikers from moving between water bodies. In more recent years the DEP has worked with the Catskill Regional Invasive Species Partnership (CRISP) and SUNY Oneonta’s Biological Field Station to check boat launch sites and boats for AIS. Their method of preventing the spread of AIS on boats and equipment involves checking boats for invasive species, draining, disinfecting and cleaning the boat and letting it dry before entering another water body. This study is another way the DEP is working to stop the spread of AIS, through early detection and quick response.

METHODS

A survey protocol was developed based on the data sheet presented in Figure 3 and was

employed at each survey site. Reservoir sampling sites were determined at the time of the survey; we aimed to obtain relatively even coverage around the reservoir shoreline, sample a variety of habitat conditions, and note all AIS observed. Each reservoir survey included both shoreline and open-water sites, which were accessed by motorboat following DEP security and safety protocols; all BFS personnel were authorized to access the reservoirs and were issued DEP identification cards (worn at all times). Tributary sites were located upstream of the reservoir’s influence where the stream could be accessed by road (within 500 ft from confluence with the reservoir). A multitude of sampling techniques were used at each site in order assess invertebrate, plant, and algae communities for the presence/absence of the 23 previously mentioned AIS of concern to the DEP (Table 1). Between shoreline sample sites, the shoreline was observed with binoculars to note the presence of scattered individuals (such as L. salicaria) that were already documented at multiple sites around the reservoir.

Tributary and reservoir shoreline site sampling procedure was as follows. Substrate sieving,

triangle nets, and hand picking were used in the stream beds and from the reservoir shoreline outward to a water depth of roughly 1 meter to determine the presence or absence of invasive benthic invertebrates. A plant rake (fashioned from two garden rake heads welded back to back) was used to assess submerged rooted plants in zones where such plant growth was anticipated (littoral zones). General observations were made along the shoreline for emergent plants, macrophyte fragments, and algae on rocks, etc. In the case of reservoir sites, additional observations of submerged aquatic plant communities were made when approaching and leaving the shoreline. In the case that specimens could not be definitely identified in the field, verifications were made at the BFS laboratory, using a dissecting microscope when necessary. Invertebrate specimens were preserved with 70% ethanol in labeled vials or museum jars; plant specimens were bagged and labeled accordingly. At open water sites on the reservoirs, water depth was determined using a depth sounder to assess suitability for rake toss sampling. Zooplankton were collected with a 80 µm mesh plankton net towed behind the boat; samples were inspected on-board for conspicuous zooplankton, preserved with 70% ethanol and brought back to the BFS for microscopic assessment.

Habitat type and sampling logistics for each site were detailed on the collection form. Habitat description included whether the site was lentic or lotic, in addition to the substrate conditions: decomposing organic matter, mud, sand, gravel, cobble, and/or boulder. Sampling logistics included substrate sieving, hand picking, plankton tow, rake toss, observation and microscopic evaluations, which meant using all of the sampling techniques at a site.

Data collected at each site were recorded both on digitally and on paper forms (Figure 3).

The location/ reservoir name, site number, date, collector names, and coordinates were recorded, including any additional comments relevant to the site. Positional data (GPS coordinates) were obtained with a Trimble GeoXT device. TerraSync software interface was programmed by DEP GIS specialists to meet DEP data quality requirements and to allow for the input of survey data at each site location. Photos were taken for documentation.

Figure 3. NYCDEP Aquatic Invasive Species Survey Sample Sheet used in the field for recording the presence/absence of species as well as site conditions and how and where they were found.

When travelling between tributaries or reservoirs we rinsed our shoes and equipment in salt water to disinfect them before entering another waterway. The boat and trailer was power washed with hot water in order to remove any specimens that may have gotten in or stuck to the equipment so as not to transport invasive species from one waterway to the next.

Data files were uploaded to a desktop computer using the Data Transfer application and

emailed to the DEP Invasive Species Specialist for GPS correction and validation, as required for NYC DEP’s data quality assurance. Maps were created from the resulting GIS datasets by the DEP’s Invasive Species Specialist.

RESULTS

Table 2 lists the tributaries and their corresponding reservoirs where AIS were surveyed and recorded as either present or absent. Note that species observed in the tributaries are not always found in the connected reservoir and some reservoirs with many AIS did not have any in their tributaries. This implies there are various means by which introduction of AIS into the reservoirs occurs as well as directly by boats carrying AIS from other water bodies. Table 2. 2014 Sites for New York City Department of Environmental Protection aquatic invasive species survey. Listed are the aquatic invasive species found in each tributary and reservoir. Tributary AIS Present Reservoir AIS Present Esopus Creek Fallopia japonica Ashokan None Rondout Creek Fallopia japonica Rondout Lythrum salicaria

Orconectes rusticus Phragmites australis Potamogeton crispus

West Branch Croton River

None West Branch Lythrum salicaria Myriophyllum spicatum Orconectes rusticus Phragmites australis

East Branch Croton River

Orconectes rusticus New Croton Hydrilla verticillata

Bear Gutter Creek None Kensico Not sampled The following figures are maps constructed using a geographic information system compiling the data collected in the field. These maps show labeled points and/or lines where AIS was either present or absent at points along the shoreline where data was collected. Figures 4 through 10 indicate AIS on Esopus Creek, Ashokan Reservoir, Roundout Creek, Roundout Reservoir, West Branch Reservoir, East Branch Croton River and Bear Gutter Creek.

Figure 4. Aquatic invasive species survey at Esopus Creek, a tributary of Ashokan Reservoir. A stand of F. japonica was found at this site.

Figure 5. Aquatic invasive species survey of Ashokan Reservoir. No AIS were found in the reservoir.

Figure 6. Aquatic invasive species survey of Rondout Creek, a tributary of Rondout Reservoir. Fallopia japonica was found at this site.

Figure 7. Aquatic invasive species survey of Rondout Reservoir. Lythrum salicaria, O. rusticus, P. australis and P. crispus were all found within the reservoir. (Lythrum salicaria is not located on this map).

Figure 8. Aquatic invasive species survey of West Branch Reservoir. Lythrum salicaria, M. spicatum, O. rusticus and P. australis were all found within the reservoir.

Figure 9. Aquatic invasive species survey of East Branch Croton River, a tributary of New Croton Reservoir. Orconectes rusticus was found at this site.

Figure 10. Aquatic invasive species survey of Bear Gutter Creek, a tributary of Kensico Reservoir. No AIS were found at this site.

DISCUSSION

The presence of aquatic invasive species within these NYC reservoirs as well as their tributaries is of concern to the NYC DEP because they threaten the well-being of these vital fresh water bodies. This study provides the DEP office with information that could help them develop policies that will help prevent the spread of AIS and lower costs for control and eradication in the future. Costs of ecological and economic damages and controlling invasive species in the United States reach into the millions of dollars for individual species and into the billions of dollars when taking into account the 50,000 invasive species in the United States (Pimentel et al. 2000). Possible plans to manage AIS include physical, biological and chemical options (Harman et al. 2003). Since AIS were found in three of the five tributaries and at least four of the five reservoirs, steps need to be taken to control AIS movement through recreational vehicles entering and exiting the waterways. By surveying and mapping AIS found in the reservoirs, the DEP can take appropriate action to prevent further damage to ecosystem health and essential infrastructure (water intake pipes) by targeting these specific species.

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