Distribution of the Invasive Tunicate Styela Clava in Long Island Sound, New England, USA

Research Article

Distribution of the invasive tunicate Styela clava in Long Island Sound, New England, USA

Nicholas Brunetti and Carmela Cuomo* University of New Haven, Department of Biology and Environmental Sciences, Marine Biology Program, 300 Boston Post Road, West Haven, Connecticut 06516, U.S.A. E-mail: [email protected] (NB), [email protected] (CC) *Corresponding author

Received: 1 October 2013 / Accepted: 6 February 2014 / Published online: 26 February 2014

Handling editor: Mark Hanson

Abstract

The clubbed tunicate Styela clava (Herdman, 1881) is an invasive, solitary, club-shaped organism native to the western Pacific. S. clava has spread far beyond its native range into temperate waters worldwide, including those of Long Island Sound (LIS) on the northeastern coast of the United States. A visual inspection of public and private commercial and recreational marinas and docks located along the shores of LIS was conducted between June 2011 and September 2013. The wrack lines of public beaches and other public coastal areas were also surveyed. S. clava was found at 77.8 % of the sites surveyed indicating it has now fully colonized the Sound. It is strongly suggested that managers of neighboring waters be vigilante, and be prepared to take steps to mitigate negative impacts, should the species spread further south along the Atlantic Coast of the United States. Key words: invasion, clubbed tunicate, ascidian, vectors

has invaded (Arsenault et al. 2009). Given that Introduction Styela has few known natural predators and is an effective filter feeder, the introduction and The clubbed tunicate Styela clava (Herdman spread of this species into an area may result in 1881) is an invasive, solitary, club-shaped tunicate deleterious effects to the native species and cause native to the marine and estuarine waters of the serious economic consequences for boaters, western Pacific from the Sea of Okhotsk southward aquaculture businesses, and marinas. along the coasts of Japan, Korea, and China to The spread of S. clava outside of its native Shanghai (Cohen 2005; Darbyson et al. 2009). range is thought to have begun in the 1920s in Today, S. clava can be found in temperate marine Newport Bay, California, although it was not waters worldwide, including those of Asia, Europe, formally identified there until 1932 (Abbott and North America, Australia and New Zealand Johnson 1972; Cohen 2005). From Newport Bay, (Goldstien et al. 2011). The adult tunicate is it spread along the eastern Pacific coast of North easily identifiable by its brown, leathery, outer America and is now found from Mexico north to covering and the two siphons that protrude from Canada (Clarke and Therriault 2007; BNZ 2008; the top of the tunic (Figure 1). Although considered Cohen 2005). S. clava made its first appearance a solitary tunicate, it is often found in extremely in Great Britain in the 1950s (Carlisle 1954) dense clusters consisting of thousands of individual where it is assumed to have been transported on organisms (Osman and Whitlatch 2000; Kluza et ships returning from Korea. From there it spread al. 2006). These dense clusters may foul lines, into the waters of Denmark and France in the buoys, pipes, oyster cages, docks and other 1960s, Ireland and the Netherlands in the 1970s, submerged natural or artificial objects and can and Belgium, Germany, and Spain during the last become serious concerns in regions where Styela decades of the 20th Century (Clarke and Therriault

13 N. Brunetti and C. Cuomo

effort to document the distribution of S. clava within LIS in order to better understand the present status of its invasion and to identify the most likely vectors by which it is spreading in the Sound.

Methods

A visual inspection of public and private commercial and recreational marinas and docks located along the shores of LIS (Figure 3) was conducted between June 2011 and September 2013 beginning in easternmost Connecticut, extending west to New York City, and east again along the southern coast of LIS to Mount Sinai, New York. Marinas were chosen based on accessibility and willingness to allow data collection and represent a Figure 1. Styela clava showing open and partially open siphons. range of sizes and types of users. The wrack lines (N. Sardalla, University of New Haven, Photo Credit). of public beaches and other public coastal areas were also surveyed for the presence of S. clava. A total of 45 sites were surveyed within 25 2007). In the early 1970’s, S. clava was reported towns: 29 sites in Connecticut and 16 sites in in New York waters (Berman et al. 1992) although New York (Table 1; Figure 3). this appears to have been an isolated occurrence. Data recorded at the time of the survey included: It was next observed in Beverly, Massachusetts, location, presence/absence of Styela, average size in the 1970s (Berman et al. 1992), and in Rhode of Styela when present, and average density of Island, New Hampshire, and Maine in the 1980s Styela when present. A visual inspection was (Karney and Rhee 2009). By 1998, S. clava had made of submerged lines, the underside of docks, entered the waters around Prince Edward Island, submerged marine equipment, and wrack lines for Canada (Clarke and Therriault 2007). the presence of S. clava. When found, individuals There are some disagreements as to when were measured and, where possible, density was S. clava actually reached Long Island Sound (LIS), determined within a 60 cm diameter circular area a body of water located between the states of using a single target organism as a centroid. Connecticut (CT) and New York (NY). According Abundances were classified as High when > 50 to Whitlatch et al. (1995) and Berman, et al. organisms were found, Low when < 10 organisms (1992), S. clava reached the eastern end of LIS were found, and Medium when 10–50 organisms in 1973 while Clarke and Therriault (2007) were found. Multiple measurements were taken at suggest that it did not reach LIS until the 1990s. each site and the average abundance per site was Nevertheless, by the year 2000, large populations recorded. In addition, marina owners, workers, of S. clava could be found fouling docks and lines and patrons were shown photographs of S. clava in Groton, CT (Figure 1; Osman and Whitlatch and interviewed as to whether or not they had 2000, Fofonoff, et al. 2003). Pederson et al. ever seen them on lines or docks in the vicinity (2005) identified S. clava at three additional sites within LIS (Mystic, CT, Milford, CT, and Results Stamford, CT) and in the Peconic Bay estuary (Jamesport, NY and Greenport, NY), which is The Connecticut sites covered approximately located at the eastern end of Long Island, NY. 110 miles of coastal area while the New York These sightings have resulted in LIS being state sites covered approximately 260 miles of classified as a site where S. clava is considered coastal area. S. clava was found at 77.8% (35 out introduced but not fully colonized (Fofonoff et al. of 45) of the sites surveyed (Table 1) and in 2003). Anecdotal evidence suggests that S. clava 97.8% of the towns surveyed (Table 1; Figure 4). has spread to other sites in the Sound over the It was common for S. clava to be found at one past decade (Brunetti and Cuomo, personal marina in a town but not at an adjacent marina in observations). This study was undertaken in an the same town (Table 1).

14 New records of invasive tunicate along the United States coast

Figure 2. Historical records of Styela clava in Long Island Sound (data obtained from MIT Sea Grant College Program (MITSG), Massachusetts Bays National Estuary Program, the U.S. Environmental Protection Agency (EPA) and the U.S. Geological Survey).

Three of the recorded Styela observations 20 years. The spread of S. clava within the Sound were made with organisms that had been washed raises several questions: a) what are the main vectors ashore onto beaches in Connecticut (Table 1). responsible for its spread; b) how much of a threat Therefore, abundance data was not recorded for does the presence of S. clava pose to other these three sites as the actual attachment sites for organisms living within LIS; c) what are its Styela in these areas was not observed. The potential economic impacts on the LIS region; greatest abundance of S. clava was recorded at and d) what is the likelihood that this tunicate three sites located in Stonington and Groton in might spread further south along the eastern eastern Connecticut and at one site, Port Jefferson, Atlantic coast of the United States? in New York State (Figure 4). Abundance of S. Once S. clava is established, its expansion and clava was classified as low at 20 sites while 9 development within that region is accomplished sites contained medium abundances. via both larval dispersion and adult transport. The average size (Table 1) of individual Larval dispersion requires an adult breeding Styela at 29 sites was > 5 cm and these should be population, temperatures within the range of 15 considered as populations with reproducing adults. to 23°C (Buizer 1980; Cohen 2005; Minchin et al. 2006; Global Invasive Species Database 2009; Discussion NIMPIS 2013), salinities of 25 to 35 psu (Cohen 2005; Davis and Davis 2007; Global Invasive This study demonstrates that S. clava has fully Species Database 2009; NIMPIS 2013), and suitable invaded the LIS estuary. These tunicates can be habitats for settlement. All of these conditions found on both coasts of LIS, and they appear to are met within the LIS estuary and have no doubt have spread to all of these areas within the past contributed to the spread of Styela. Ballast water

15 N. Brunetti and C. Cuomo

Table 1. Location, site description, coordinates, Styela clava presence/absence, abundance, and average size of individuals for survey sites in Long Island Sound.

Coordinates Site Site S. clava S. clava Average Size State Town ID # Type Present Latitude, N Longitude, W Abundance of Individuals

1 CT Stonington Marina Yes 41°20'22.23" 71°54'26.46" High > 5 cm 2 CT Groton Marina Yes 41°19'32.82" 72°03'36.78" Medium > 5 cm 3 CT Groton Marina Yes 41°19'13.87" 72°03'45.86" High > 5 cm 4 CT Groton Dock Yes 41°19'12.41" 72°04'00.99" High > 5 cm 5 CT Waterford Marina Yes 41°19'31.00" 72°10'34.47" Low > 5 cm 6 CT Niantic Marina Yes 41°18'40.42" 72°12'11.11" Medium > 5 cm 7 CT Niantic Beach Yes 41°18'16.30" 72°12'16.69" Unknown Unknown 8 CT Westbrook Marina Yes 41°16'17.97" 72°28'05.03" Medium > 5 cm 9 CT Clinton Marina Yes 41°16'08.94" 72°31'30.48" Low > 5 cm 10 CT Clinton Marina Yes 41°16'07.98" 72°32'52.80" Low > 5 cm 11 CT Guilford Marina Yes 41°16'01.50" 72°40'40.80" Low < 1.2 cm 12 CT Branford Marina Yes 41°15'55.32" 72°48'09.66" Low > 5 cm 13 CT Branford Marina Yes 41°15'49.89" 72°49'02.41" Low > 5 cm 14 CT Branford Marina No 41°15'49.46" 72°49'01.23" n/a n/a 15 CT Branford Marina Yes 41°15'45.84" 72°48'30.96" Low > 5 cm 16 CT Branford Dock Yes 41°15'23.07" 72°51'03.84" Low < 2.5 cm 17 CT New Haven Marina No 41°17'33.06" 72°55'09.77" n/a n/a 18 CT New Haven Buoy Yes 41°16'55.23" 72°55'43.44" Low > 5 cm 19 CT New Haven Marina No 41°16'52.65" 72°55'47.64" n/a n/a 20 CT New Haven Beach Yes 41°15'10.62" 72°54'00.00" Unknown Unknown 21 CT West Haven Beach Yes 41°15'21.85" 72°57'14.82" Unknown Unknown 22 CT Milford Marina Yes 41°12'44.96" 73°03'21.16" Low > 5 cm 23 CT Milford Dock Yes 41°12'43.78" 73°03'12.86" Low > 5 cm 24 CT Bridgeport Dock No 41°10'32.87" 73°11'12.78" n/a n/a 25 CT Bridgeport Marina Yes 41°10'03.59" 73°09'59.29" n/a n/a 26 CT Bridgeport Marina Yes 41°09'33.16" 73°12'42.44" Low > 2” 27 CT Norwalk Marina No 41°05'33.39" 73°24'46.04" Medium > 2” 28 CT Norwalk Marina No 41°05'39.18" 73°24'47.64" n/a n/a 29 CT Norwalk Marina Yes 41°05'14.40" 73°23'38.10" Low > 1” 30 CT Darien Dock Yes 41°03'09.08" 73°28'39.24" Medium > 2” 31 NY Mamaroneck Marina Yes 40°56'22.77" 73°43'47.85" Medium > 2” 32 NY Mamaroneck Marina No 40°56'27.52" 73°43'58.97" n/a n/a 33 NY City Island Marina Yes 40°50'33.00" 73°47'00.00" Medium > 2” 34 NY Oyster Bay Marina Yes 40°52'30.22" 73°31'39.85" Medium > 2” 35 NY Centerport Docks Yes 40°53'34.74" 73°22'28.86" Low > 2” 36 NY Northport Marina No 40°53'22.37" 73°21'17.32" n/a n/a 37 NY Port Jefferson Marina Yes 40°56'48.04" 73°04'09.72" High > 2” 38 NY Port Jefferson Marina No 40°56'53.66" 73°04'01.81" n/a n/a 39 NY Mount Sinai Marina Yes 40°57'50.36" 73°01'16.18" Medium > 2” 40 NY South Jamesport Marina Yes 40°56'04.20" 72°36'32.40" Low > 2” 41 NY Mattituck Marina Yes 41°00'34.20" 72°33'01.20" Low > 2” 42 NY Mattituck Marina Yes 40°59'04.45" 72°31'32.42" Low > 2” 43 NY Greenport Marina No 41°06'30.00" 72°21'18.00" n/a n/a 44 NY Greenport Marina Yes 41°06'39.66" 72°21'32.82" Low > 2” 45 NY Orient Point Marina Yes 41°09'09.60" 72°14'37.38" Low > 2”

transport of Styela larvae into LIS is less likely which S. clava spreads from one region to another owing to their short (~ 48 hour) larval phase (Darbyson et al. 2009). If adults are transported (Clarke and Therriault 2007); however, it cannot to an area favoring their survival and reproduction, be completely discounted. they are able to establish new populations there, Transport of adult Styela on lines, ship hulls, which, in turn, grow and expand within the local cages, and other moveable marine equipment is area via larval settlement. The spread of Styela in thought to be the primary long-distance mode by this manner should result in spatially isolated

16 New records of invasive tunicate along the United States coast

Figure 3. Long Island Sound study area with sampling sites marked by site identification number listed in Table 1.

Figure 4. Relative abundance of Styela clava in Long Island Sound (by site).

17 N. Brunetti and C. Cuomo

populations throughout a region. Such populations (Minchin and Duggan 1988). High fouling densities should be associated with recreational and of Styela are associated, worldwide, with negative commercial vessels, marinas, docks, and pilings. impacts on native populations of filter-feeding The distribution of Styela populations within LIS organisms and fouling of docks, lines, pipes and appears to reflect this pattern of spatially marine-related equipment (Clarke and Therriault isolated populations associated with marinas and 2007). Dense populations of Styela rapidly docks throughout LIS. A close examination of deplete local waters of plankton, leaving little the data reveal that even within marinas located behind for native filter-feeders in the region, in the same town, Styela occurs at one and not at including many commercially important bivalves the other supporting the idea that Styela (LeBlanc et al. 2007). Additionally, massive Styela colonization of areas within LIS has mainly been populations also out-compete native species for due to adult transport. space (Stoecker 1978). At present, few dense Styela The general flow of surface currents in LIS is populations have been identified in LIS (this from East to West along the North shore of the study). Whether or not the existing LIS populations Sound and West to East along the South shore of of Styela will ever develop into massive the Sound (Codiga and Aurin 2007). If Styela was populations remains an open question. At present, simply spreading westward via larval dispersal the colony density does not appear to pose a from the Groton, CT area, one would expect it to threat to native filter-feeding organisms nor to be spreading relatively linearly, in a westward have significant economic impacts in the region. direction, along the north shore of the Sound. As The invasive tunicate S. clava has fully well, one might expect denser populations to be invaded the LIS estuary of the United States. found in the northeastern and north-central Given that the known temperature tolerances for portions of the Sound corresponding to the breeding populations of S. clava range from 15 length of time a colony was established. The less to 23°C (Buizer 1980; Cohen 2005; Minchin et dense populations and possibly isolated individuals al. 2006; Global Invasive Species Database would be more typical of the northwestern and 2009; NIMPIS 2013), LIS might be expected to southern regions of the Sound. The present represent the southernmost area likely to be fully distribution and abundance of S. clava in LIS colonized along the east coast of North America. supports the concept that the spread of Styela However, there have already been sightings of S. along the north shore of LIS was the result of clava in the coastal waters of New Jersey, simple larval dispersion from the initial adult suggesting that S. clava may be able to invade population located in Groton, CT. Similarly even further south along the east coast of the surface current transport of larvae from West to United States. Preliminary work suggests that East might explain the distribution of S. clava adult Styela may, in fact, be able to tolerate along the south shore of LIS. Surface current temperatures as high as 30°C (Cuomo, unpublished transport of larvae, however, does not totally data) although whether or not adults can reproduce explain the high abundance of Styela found in Port at these temperatures is unknown. It is strongly Jefferson, NY, at a ferry terminal that is situated at suggested that managers responsible for LIS the mid-point, of the sites located along the south waters, as well as those of neighboring waters, shore of LIS. The number of occurrences of Styela closely monitor the status of the populations at marinas observed in this study and the relative within the Sound and be prepared to take steps to paucity of Styela observed on natural rock mitigate negative impacts should the populations outcrops, along with the fact that Styela often was become dense or spread further south along the found in one marina but not in an adjacent Atlantic Coast of the United States. marina, points to the potential importance of human-mediated transportation of Styela spread in the Sound. At this point, it appears highly Acknowledgements likely that both vectors – larval transport and This work was supported, in part, by funds from the URS and adult transport - are responsible for the spread of SURF programs of the University of New Haven. The authors S. clava throughout the Sound. would like to acknowledge P. Bartholomew and K. Sandin for Regardless of the vector, S. clava now appears assistance in the field. The authors would also like to thank the to be firmly established throughout LIS although two anonymous reviewers and J.M. Hanson for their helpful comments. most populations have not yet reached the fouling densities (> 1000/m2) found elsewhere

18 New records of invasive tunicate along the United States coast

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