I1:\DARRIN 'SrI Fresh Water Institute Lake George, New York Adirondack Field Station at Bolton Landing A SURVEY OF TRIBUTARTRS IN THE NORTH BASIN OF LAKE GEORGE, NEW YORK FOR TH F: PRESENCE OF EURASIAN W ATERMILFOIL prepared for The Fund for Lake George by Lawrence W. Eichler Research Scientist & Charles W. Boylen Associatt: Director Darrin Fresh Water Institute Rensselaer Polytechnic Institute Troy, NY 12180-3590 Bolton Landing, NY 12g14 DFWT Technical Repolt 1U03-4 TABLE OF CONTENTS The Survey of T,ake George Tributaries for Eurasian watcrmilfoil- 2002 ExecLllive Summary III Inlroduction 1 Methods Results and Discussion 3 References 12 Acknowledgements 12 Appendix A. Site Locations Appendix B. Macrophyte Community Assessment data 11 Executive summary A survey of the tributary deltas in the northern portion oftbe Lake George basin was conducted in 2002 to assess the extent o[Eurasian watermilfoil (Myriophyllum spicatum L.) infestation. The project was conducted by the Darrin Fresh Water Institute with Gnaneial support from the Fund for T.ake George. Similar surveys of the northern basin were completed in 1988, 1990, 1993, 1996 and 1999 as reference points. Stream delta areas \vere chosen as n:adily identifiable points which historically harbor diverse assemblages of native aquatic plants. Results of these surveys can he used to approximate the rate of spread of Eurasian watermilfuilthruugh the Lake George basin. Tn 1988, when tributary surveys were initiated, 22 percent of the sites in the northern third of the Lake Creorge hasin were found to have Eurasian watermilfoil. By 1990, this percentage had increased to 39 percent with a gain 01'7 new Eurasian waternlilfoil sites. By 1993, the percentage oftributmy sites Witll active Eurasian watennilfoil populations had declined slightly to 37%. The decrease was due to hand harvesting of five sites in this ponion of the lake basin. Discovery of four new Eurasian watermil foil sites during the 1993 survey, however, reduced the overall impact of management activities to a net loss of one active Eurasian watermilfoil site. In 1996, a total of 17 sites (42%) had Eurasian watennilfoil, with 2 sites (5%) producing milfoil for the first time. Of the two new Eurasian watennilfoil sites, hoth were restricted to a few plants which were removed. The 1999 survey of the north basin identified 3 new sites (7%) with milfoil present for the first time in the history o[the tributary surveys. A total of I g sites (44%) had milfoil present at the lime of the survey in 1999. All three of the new sites were clearcd of milfoil via hand harvesting. In 2002, no He\v Eurasian watcnnilfoillocations were recorded by the Tributary Survey, however 17 sites (42%) surveyed still supported EuraSIan watennilfoil. fourteen of the 27 sites tllat were positi ve [or mil foil by 1999 had heen clearcd by hand-harvesting or other methods prior to 2002, and have been positive on at least one occasion since the initial hanresting. Thus not only initial colonization but also re-colonization of tributary sites by Eurasian watennilfoil is occuning in Lake George. The rate of colonization, howcver, is variable from year to year and hetween the three portions of the survey. Smce 1990, the number of tributary sites in tIm portion of the Lake George basin with Eurasian watertlHlfoil present has remained fairly constant. This is largely due to management effol1s supported by the US EPA Clean Lakes Program, the Lake George Park Commission, and the Fund for Lake George. Eurasian watermilfoil continlles to sprcad through the Lake George hasin with an increase in known Eurasian watennilfoil locations of between six and fifteen per year. MaJlagement cflorts to date have been implemented at 132 urthe 144 known Eurasian \vatennilfoilloeations. These management eff0l1s have reduced the Eurasian watennilfoIi biomass at these localions. However, Eurasian watcrrnilfoil has only been eliminated at a handful of sites and reintroduction at thesc locations is likely. At this time, EurasiaJl watermilfoil is ranked 10th by relative abundance (a runetion of mean percent cover), and 29th by frcquency of occurrence for the 39 species found ill the current survey. The fact that Eurasian iii watennilfoil has reached this level of abundance is a testament to the rapid spread and highly competitive nature of this species. There is no evidence that loss of Eurasian watennilfoil populations at specific sites in Lake George can he attributed to natural mortality. ThLls maintenance becomes critical following initial management. Maintenance will require site visits yearly or every other year to harvest regrowth. A program to continue maintenance activities iollowing the conclusion of Federal funding in 1993 was deemed imperative. Since 1995, Eurasian watem111foil management in Lake George has been conducted under the auspices of the Lake George Park Commission. Physical controls including hand harvesting, suction harvesting and benthic barrier have been employed since 1995. This program will continue through 2003, with current efforts contracted to Lycott Environmental Services, Inc. A pilot program for herbicide testing was dealt a sethack in 2002 by its failure to acquire a permit from the Adirondack Park Agency. Negotiations continue to acquire the necessary pennits for future herbicide testing. financial support for this program should be sought at local, region8l and fcdcrallevels. Local support exists through the FUND for Lake George, however fincmcial support at th0 state and federal level is also necessary. Introduction Streams entering Lake George, with nutrients and sedimcnts dcrived from the terrestrial porlion of the basin and deposited on their delta.. , are prime locations for the continued establishment of Eurasian waterrnilfoil (Myriophyllum spicatum L.). Delta areas are also disturbed habi1<lts, as a result of sedimentation of terrestrially derived materials and scouring of existing sediments at times of accelerated runoff. The combination of sediment conditions and habitat disruption make tributary deltas prime locations for Eurasian watermilfoil infestation. Around the entire lakeshore, there are 128 listed stream tributaries (Madsen et aL 1(89). "Recausc human activity in the Lake George basin has historically exacerbated water conditions. relative to disturbed areas, the rate of establishment and spread of milioil has been of particular concern in the management of Eurasian watennilfoil. A survey of all the tributaries in the basin was perfornled as part of the 1987~88 Lake George Aquatic Plant Survey (Madsen el al. 1989). The survey provided a procedure for finding new sites with Eurasian watermilfoil, including the establishment of a regular search pattern for milfoi[ sites to ascertnin the relative distribution of milfoilllillong the native plant communities in Lake George. In order to balance the number of tributary sites surveyed in each year and to stabilize the cost of the survey, the south basin tribularies were divided into two groups in 1991. With approximately 45 tributaries in each group, a three~year cycle of surveys has been established with a south, central and north component of nearly equal number of tributaries. The tributaries of the north basin were the subject of the 2002 survey. The north basin tributary SllTvey was conducted in 1988, 1990, 1991, [996, [999 and 2002 in order to provide information on the rate or colonization of Eurasian waternlilfoil. Since these are readily located sites for whieh the presence or absence of Eurasian watermilfoil was known. these sites were revisited in 2002 to detennine whether appreciable new infestation, re-invasion or natural mortality of earlier infestation had occurred. Methods The shoreline adjacent to tributary outflows in the north basin was surveyed for the presence of Eurasian watermilfoil. The tributaries comprising this portion of the survey were visited betwecn July 30th and October 9th. 2002. Surveys consisted of swimming a I 00~111eter segment of shoreline from the water's edge to the outer edge of the littoral zone. Diver swimover transects were also completed at each si.te in order to characterize the macrophyte community present. Divers skilled in plant identification estimated the abundance or all w..[uatic planl species in each 1 meter (3 fl) depth interval using the following abundance classes: Class Code % Cover Range Centroid Abundant A greater than 50% cover 75.0% Common C 25% to 50% cover 37.5% Pn:senl P 15% to 25% cover 20.0% Occasional 0 5% to 15% cover 10.0% Rare R less than 5% cover 2.5% Percent cover data provides both the average depth distribution of the plants present and an estimate of the relative abumlam.:e of specics at thc tributary sites. This infonnation is also important for future management decisions concerning 111ilfoi1 control alternatives and permil applications required as part of any control strategy. A map showing the general location of this year's survey activity is shown in Figure 1. Specific tributary locations in the current survey an: provided in Appendix A. Figure t. Map of Lake Gcorge indicating the region included in the 2002 Tributary Survey. N 2 Results and Discussion The current survey included the l1orthemmost portion of the lake basin tributaries (41 sites). The southern and central portions of the lake basin were completed in 2000 and 2001, respectively. Maps with the 10l:alions of the tributaries surveyed in 2002 are provided a" Appendix A. The 41 sites surveyed in the 1988, 1990. 1993, 1996 and 1999 programs were replicated in the 2002 survey. Methodologies employed by the three surveys were the same. The resulls of the north basin tributal)' survey for all survey yenrs nre presented in Table 1. For each site, the tributary nwnber and site name is given. Table 1. Tributary survey sites and the presence (Y) or absence (N) of Eurasian watermilfoil. Tribulary if SITE NAME UAI1! 20{)2 1999 1996 1993 1990 1988 T-l OPPOSITE ROGERS RK 3-Sep-02 N N N N N N T-IA MOSSY POINT 3-Sep-02 Y Y Y Y Y Y T-2 C,I.ENRURNIF.