Background:

This survey of submergent aquatic vegetation in Lake Nancy was conducted by Scott Kishbaugh of the NYSDEC and Laurie Kline from the local community, as requested by the residents of Lake Nancy.  An aquatic plant survey was conducted by the NYSDEC in 1999, and this survey will be utilized as a baseline for comparing changes in the lake.  It is presumed that the surveys in 1999 and 2005 accurately reflect conditions in the lake during those years, an assumption which is usually reasonable for submergent aquatic plants.

PLANT SURVEY Methods:

The present survey involved rake tosses and sample collection along the entire shoreline of the lake, and in select areas of the open water. Rake tosses utilized a two-sided rake tethered to a measured nylon line. Two rake tosses were performed at each sampling location. Plants collected through the rake-toss method were separated and enumerated qualitatively, using a scale developed by Robert Johnson and Paul Lord from Cornell University.  The abundance of plant material on the rake was listed in the following classification system:

Z = zero = no plants found on the rake

T = trace = a fingerful of plants found on the rake

S = scarce = a handful of plants found on the rake

M = moderate = plants covering the entirety of the rake

D = dense = sufficient abundance to limit the ability to lift the rake out of the water

Coverage of individual plant species (within the mass of plants on the rake) were also classified using the same system.  Additional plants observed in the lake but not pulled by the rake, such as emergent or floating plants (including small plants such as duckweed or watermeal, as well as larger macrophytes such as lilies and pickerel weed), filamentous algae, and other plants observed on the lake bottom, were also recorded, and relative abundance of these plants was also estimated.  Two rake tosses were conducted at each sampling site, and the latitude and longitude of sampling sites were recorded. 

PLANT SURVEY Results:

The plant survey identified a least a dozen separate aquatic plant species, and it is clear that there are other native plants that are present but were not visible from the lake surface.  This is generally indicative of a healthy and diverse aquatic ecosystem, and should be maintained regardless of future plans for the lake.

An incomplete species list of submergent aquatic plants in the lake is listed below, with the typical range of plant abundance found within the lake, listed in overall (decreasing) order of abundance.  Plants listed as “S” are solely submergent, “F” are solely floating leaf plants, and “SF” are submergent plants with a floating leaf. It should be noted that all of these plants are native to New York State, and have probably been found in Lake Nancy for much of its history:

Common Name	Scientific Name	Abundance Range	Overall Abundance
Watershield (F)	Brasenia schreberi	None to Dense	Moderate to Dense
White water lily (F)	Nymphaea sp.	None to Moderate	Scarce to Moderate
Narrow leafed pondweed (Snail-seed pondweed?) (SF)	Potamogeton bicupulatus?	None to Dense	Trace to Moderate
Cutleaf watermilfoil (S)	Myriophyllum pinnatum	None to Moderate	None to Scarce
Ribbonleaf pondweed (SF)	Potamogeton epihydrus	None to Moderate	None to Scarce
Minor bladderwort (S)	Utricularia minor	None to Moderate	None to Scarce
Largeleaf pondweed (SF)	Potamogeton amplifolius	None to Dense	None to Scarce
Common bladderwort (S)	Utricularia vulgaris	None to Scarce	None to Trace
Water stargrass (S)	Heteranthera dubia	None to Scarce	None to Trace
Eelgrass (S)	Vallisneria americanum	None to Scarce	None to Trace
Yellow water lily (F)	Nuphar sp.	None to Scarce	None to Trace
Muskgrass (S)	Nitella sp.	None to Scarce	None to Trace
Mare’s tail (S)	Hippuris sp.	None to Scarce	None to Trace
Unidentified bladderwort (S)	Utricularia sp.	None to Scarce	None to Trace

The aquatic plant communities differed somewhat in each part of the lake. The northwest cove, near the inlet, was dominated by an undercarriage of the cutleaf milfoil (which may have actually been Myriophyllum farwelli, or Farwell’s milfoil- these are difficult to distinguish without a flowering bract above the lake surface, which was not yet present on these plants), large leaf pondweed, and the ribbon leaf pondweed, although the shallowest area, closest to the inlet, was dominated by the narrow-leaf pondweed (which may be snail seed pondweed, or Potamogeton bicupulatus- these plants are notoriously difficult to identify). The surface was dominated by watershield and white water lily, but these were largely restricted to the shoreline or where the water depth was less than about 6 feet.

Along most of the shoreline, water shield was the dominant plant, although heavy populations of the white water lily were also found.  The low-lying plant community was very different from one shoreline to the next, and often varied outside of each group of houses.  This variability is common in many lakes. Along the western shore, the cutleaf milfoil, the minor bladderwort, and the snail seed pondweed were the most common, although none were found in more than “scarce” quantities.  The southeastern shore and northeast cove had “moderate” quantities of the cutleaf milfoil, but these plants were also not seen at all in some other nearby locations.  The ribbon leaf pondweed was more common along the southern and eastern shores than the western shores, and the few patches of yellow water lily were seen in these areas.  The northeast cove also had moderate to dense populations of the large leaf pondweed and the minor bladderwort, but lower densities of the white waterlily and watershield than in some other parts of the lake (although the inlet to this cove did have larger watershield populations). In the open water (center of the lake) areas, the same general mix of milfoil, bladderwort, and pondweeds also occurred.

In short, the underwater (submergent) aquatic plant growth was densest in the northwest and northeast coves, while watershield and white waterlily dominated most of the surface of the lake, with the densest populations near the inlets along the northeast and northwest bays and along the east side, and in patches along other shorelines. Dense subsurface weed growth was quite uncommon, although surface plant growth was dense in several areas.

Many of the same plants reported in the 1999 survey were found in the 2005 survey, as expected.  However, in 1999 the submergent aquatic plant community appeared to be dominated by large-leafed pondweed, bladderwort, and cutleaf milfoil, and the floating leaf plant population was not extensive.  In 2005, the submergent plant community was perhaps more diverse, although the cutleaf milfoil, snail shell pondweed, and ribbon leaf pondweed were probably the most extensively growing underwater plants, and the floating leaf plant populations, particularly watershield, were more extensive.

The very limited water quality surveys indicate that Lake Nancy is a weakly dystrophic lake- this refers to lakes that have naturally brown (weak tea-colored) water due to the organic makeup of the soils and vegetation types along the shoreline and underlying the lake. The slight brown color comes from weak organic acids which create a slightly acidic environment- this can also be seen by the presence of the bladderworts and cutleaf milfoil, both of which are slightly acid-tolerant plants. Water clarity measurements were fairly low (less than 2 meters), but limitations on water transparency probably derive from the natural water color, not excessive algae growth. In fact, very little algae was observed, either as planktonic algae (green dots suspended in the water) or planktonic algae (filaments or strands floating on top of rooted weeds or sitting in the bottom).  Most of the algae was observed as green “bushels” nestled within weed beds, usually floating between the surface and bottom in fairly shallow water, but these bushels were few and far between.

            Oxygen readings were depressed near the lake bottom at the deep hole.  The samples collected from this depth had a slight hydrogen sulfide odor, which occurs when sulfates in the water (common to all lakes) are converted to hydrogen sulfide gas in the absence of oxygen.  These samples also had a slight yellow color, probably due to a concentration of dissolved organic material within this sample.  These phenomenon are fairly common in deepwater lakes, but less so in shallow lakes.  It is presumed that this oxygen-depleted water makes up only a small percentage of the lake volume- the portion of the lake close to this depth is very small, and most of the lake is probably well mixed and fully oxygenated.  While this was not explicitly measured, the appearance and viability of the plants and sediment collected at all depths under 12 feet (all plants were green and healthy, and the sediment was brown, rather than black and heavily decaying) indicate that oxygen deficits are probably not a significant concern at the lake.

PLANT SURVEY Discussion:

In the 1999 survey, it was estimated that, as observable from the lake surface on a day when the lake was relatively clear, that less than 20% of the lake area appeared to be covered by plants. A similar estimate could probably apply for the 2005 survey as well, since (except for the coves) most of the lake more than about 100 feet from the shore did not have surface plant growth.  However, close to 100% of the lake bottom exhibited at least submergent plant growth, even in the center of the lake, and dense surface plant growth was more common in the shoreline regions than in 1999. The watershield and waterlilies are growing much more extensively in 2005 than in 1999.  While some of the submergent plant species, such as the narrow leaf and ribbon leaf pondweeds, may have increased in abundance, these appear to be growing at even moderate levels only in the shallowest coves, and these are unlikely to create any ecological or aesthetic problems.  and would most likely be the target for any proposed lake management activities.

In 1999, one of the recommendations was that there was not sufficient plant growth to warrant lakewide plant control. As will be discussed below, lakewide plant control in 2005 may still not be appropriate, since the low-lying submergent plants in much of the lake may have prevented more extensive surface growth of the watershield and lilies.  For lakes without extensive power boating traffic, shoreline vegetation is less of a management issue, since there are far fewer boat props and trailers to get tangled in weeds, and canoes and kayaks are much easier to maneuver through weed beds.  However, for swimmers and some boaters, the shoreline plant stands, particularly those associated with the water shield, may be extensive enough to warrant management.  In particular, the heavy gelatinous film on the watershield plants may be bothersome to swimmers and anglers.

That said, decisions about managing aquatic plants are within the purview of lake residents. This survey suggests that extensive weed growth is limited to only isolated areas of Lake Nancy, and is likely to create far fewer recreational or aesthetic impacts on this lake than on other lakes with either more extensive motorboat traffic or denser submergent weed growth. However, the role of the NYSDEC is to evaluate risks associated with the use of some lake management techniques (those for which the DEC has a regulatory or permitting program in place), not to identify either the need for management or prioritize the benefits of this management. Within the confines of this review, however, the NYSDEC can provide some guidance about the likely success of various management techniques, and identify the permitting structure in place for each of these activities.  These are discussed below.

PLANT Management Options:

Prior to devising and implementing any plant management strategies, the lake residents need to determine if the no-action alternative is appropriate.  This is important not only to gain sufficient local consensus about the necessity of conducting these plant management strategies, but also to satisfy the requirements of permitting agencies, at least in the case of the permitting programs in place for the use of grass carp and aquatic herbicides. In particular, need will probably have to be demonstrated if the lake is classified, in whole or part, as an Article 24 wetland (referring to the portion of the environmental conservation law which regulates wetlands).  I don’t know if the lake is a wetland in whole or part- I’d suggest contacting Ken Kogut from the Warrensburg office (518-897-1290) for more information about the wetland ”status” of the lake.

Whole Lake Versus Shoreline Management:

If such a need to manage the plant communities can be agreed upon, the next issue concerns whether local (individual bed/dock/cove) or whole-lake management is warranted.  As discussed above (and below), while the vast majority of the lake is inhabited by submergent aquatic plants, most of these are low-lying plants that rarely reach the lake surface. Even in those cases, surface growth is usually limited to a small (football-shaped) leaf that is often only visible within near proximity of the plant.  There are no doubt some depth and sediment limitations to the range of the watershield and water lily growth (both generally grow in less than 6 feet of water), but it is quite possible that these low-lying plants are preventing the spread of these floating leaf plants into deepwater water and other shallow-water habitats, simply because they are presently occupying that space. There are certainly some shallow-water areas of the lake that are not presently colonized by the watershield and lilies that would be appropriate habitats for these plants, if not for the lack of room for the plants to establish. More importantly, wholesale lakewide control of all aquatic plants could result in a barren underwater landscape that could easily be recolonized by the plants you are attempting to control- particularly the lilies, since the underwater tubers are resistant to some lake management activities- or by other submergent invasive plant species that are found in many nearby lakes and could easily migrate to Lake Nancy.  For these reasons, and since the “impact” from invasive plants is more likely limited to shoreline areas, whole lake management may create more problems than it would solve.  However, each of the management strategies discussed below will address both shoreline and whole lake control, particularly since some of them can be “applied” locally/topically.

The following management strategies could likely be considered, with the assumption that watershield (and perhaps water lily) control could be the focus of the management strategy:

A. PHYSICAL/MECHANICAL CONTROLS

General- these strategies require the fewest permits, can more easily be employed locally, and often have the fewest side effects (or at least the fewest unexpected side effects, whether ecological, economic, or related to public acceptance of the management activities).  They are usually labor intensive and short-lived, with the longevity of the “treatment” largely, and often unpredictably, dictated by the mix of target and non-target plants, reintroduction rates of target plants, weather conditions, the treatment itself, and many other factors. 

Strategies Most Likely to Be Effective

Benthic barriers- these are plastic mats or screens placed on top of the weeds.  Their mode of action is cutting off the sunlight and ultimately “starving” the plants of the light necessary to photosynthesize.  The barriers are typically left in place for at least 30 days, although barriers are often left permanently in swimming or high use boating areas.  They need to be anchored down and holes need to be poked through the material to prevent CO₂ bubbles formed by plant degradation from lifting the mats.  The mats also need to be cleaned periodically to prevent plants, especially loosely rooted plants like bladderwort, from growing on top of the mats.  The mats will kill everything they cover, so it is not as selective as hand-pulling, but it can “treat” larger areas.  This strategy, however, becomes less attractive in larger areas, since diver time (to site the mats) and professionally manufactured materials can be quite expensive (>$1000 per acre).  This is usually limited to beach areas and to open common navigational channels.  This doesn’t require a DEC permit (assuming the lake is not a wetland).  This strategy, however, may be the most appropriate for controlling both water shield and lilies, particularly if volunteer time (from lake residents) can be utilized to implement the strategy, and if more traditional bottom barriers, such as green plastic garden tarps, are utilized.  This should be limited to areas necessary to open a boat channel or swimming zone.

Strategies Likely to Be Effective in Some Areas/For Some Plants:

Hand-pulling (a.k.a. hand harvesting)- this is akin to weeding your garden.  Only target plants are removed, and by removing the root structure, seeds, and all flowering parts, longer-term control can be expected once the seed base in the sediment is depleted.  This is also the cheapest, by far, of the strategies. 

This strategy can be effective at controlling water shield, since this plant is not strongly rooted. However, it is generally not very effective at controlling water lilies, since they are very strongly rooted and the underwater rhizomes (tubers) are very large and difficult to dislodge. Moreover, this strategy will quite become tiresome (in more ways that one) for very thick, large beds.  As such, this strategy is best employed in areas with scattered plants, or in areas when new, single plants first arise, especially after some other strategy has temporarily eradicated or substantially knocked down the plants. In deeper areas, pullers should use a nylon small mesh divers bag for plants and fragments- in these areas, this would probably require a scuba diver, although it can be achieved by snorkelers in the depths of concern in Lake Nancy. This doesn’t require a DEC permit.

Hand Cutting- this involves using a cutting bar or other mechanical scythe to cut the top of the plants.  This differs from “mechanical harvesting” (see below) in that it is only done along shorelines or other small areas by individuals, and thus can be well controlled.  The advantages and disadvantages of cutting operations are discussed in more detail below. If the hand cutting is also accompanied by harvesting and removal of the cut plants (either by boat, by “booms” that can contain the cut material, or skimming the surface), and is limited only to those plants that create problems (the floating leaf plants) instead of the low-lying plants that spread by fragments (milfoil, bladderwort, and some of the pondweeds later in the summer), this may be manageable.  It is essentially a maintenance program, but one that can keep the top of the lake open for recreation.  Once this operation extends beyond immediate shoreline areas, it becomes more like mechanical harvesting, which has additional disadvantages.  These generally don’t require a DEC permit if the bottom is not disturbed in the process. 

Water Level Manipulation- also known as drawdown, this involves lowering the water level to freeze the root structure of the target plants.  Both watershield and water lilies are usually controlled by a winter drawdown, and this may be effective at controlling the growth of these weeds near the shoreline.  However, it does not appear that the lake can be drawn down sufficiently (> 6 feet in vertical depth) to expose the outer (deepest) edge of these plant beds, so the plants could recolonize the shallower water from the unexposed reservoir of plants in the deeper water.  Many of the other low-lying plants in the lake would also be affected by the drawdown, rending the lake susceptible to colonization by other plants.  And there remain concerns about refilling the lake in the spring to get back to the normal spring and summer water levels for adequate lake access (and water pipes and other lake uses). For these reasons, winter drawdown may only be appropriate for the shallowest areas (for dense weed beds in < 3 feet of water).  DEC permits may be required if nearby wetlands are impacted by the water level loss.

Shading- these are liquid dyes that inhibit photosynthesis by preventing certain wavelengths of light from reaching rooted plants.  This method is not listed under the Chemical Control section below because its mode of action is physical (light inhibition), not herbicidal.  The dyes turn the lake water blue, and will break down naturally (due to sunlight) in 6-10 weeks.  Since the expected retention time in Lake Nancy is approximately 5 weeks, there is a good chance that the dye would wash out of the lake prior to achieving full effectiveness, particularly since most spring treatments occur during a period of significant snowpack runoff (and thus high water transfer in the lake).  However, if the lake is drawn down before the treatment, additional contact time might be achievable.  There are restrictions on using the treated water for drinking, but not for swimming.  The cost for the chemical, which would need to applied at a rate to color the entire lake, is about $60 per gallon to treat 4 acre-feet (4 acres of water 1 foot deep), and Lake Nancy has approximately 600 acre-feet of water, so the expected cost would be about $8,000.  The longevity of the treatment is not easily predicted, but it is probably unreasonable to expect more than a few years (at most) of control with a single application.  The primary shading agent used is called Aquashade; however, this chemical requires a NYSDEC application permit, since it claims herbicidal-like action on its label.  There are other similar products that, due to different claims on their label, do not require at least a DEC permit.  I’d suggest contacting John Bennett, the Region 5 pesticide manager, at 518-623-3671, for more information about shading products.  Although these are used frequently in NYS, there is very little information about their effect on larger lakes such as Lake Nancy.

Strategies Less Likely to be Effective (or Less Practical):

Mechanical Harvesting- or lake lawn cutting.  This involves using a large barge with a cutting bar, conveyor belt, and storage hopper to remove weeds in a swatch 6-10 feet wide and 6-8 feet deep.  It will certainly cut these plants, particularly the tops of the watershield and lilies, but it will spread some of the low lying plants (the milfoil and the bladderwort in particular) to other regions of the lake, since these plants often become established from fragmentation. Even if the fragments that are inevitably created by the harvesting do not cause new weed growth (though they probably will), the wind will probably move the cut bushels and create more surface disturbance.  There also does not seem to be a logical place to load the barge into the lake.  Finally, the cost to purchase a mechanical harvester is very steep (appx. $125,000-150,000), and leasing harvesters is becoming more difficult, since so few harvesters are available for lease.  For these reasons, this strategy is also not likely to adequately control the problem without creating new problems.  I’d also place the other cutting/harvesting management strategies, such as rotovating and dragging bed springs, in this category, due to the excessive fragmentation, although individual cutting that can be well controlled (as discussed above) may be more appropriate, particularly if the fragment-spread plants such as the milfoil and the bladderwort are not cut in the process.

Dredging- this is the most extensive and expensive lake management tool available, and involves removing bottom sediments.  This will both deepen the lake and remove the aquatic plants/stems/roots anchored in this sediment.  This could be done by a hydraulic dredge, if the lake is not completely drawn down, or earth-moving equipment if the lake is drained.  A large area would be required to dump and dewater the sediment-water slurry removed from the lake, and a large launch area would be needed to move the dredge barge to and from the lake.  All of this would be quite expensive (probably >>$100,000-200,000). More importantly, however, the sediment layer above hardpan (whether bedrock or compact soil) is probably not very thick in many of the places where these plants grow (except in the inlet cove), and the lake is clear enough that lowering the bottom will probably not cause light limitations to reduce weed growth.  So while this strategy will probably reduce weed growth by removing plants, it will be less effective at reducing long-term growth, a benefit that would probably be necessary to justify the extremely high cost and rigorous permitting process required to dredge.

B. CHEMICAL CONTROLS (Herbicides)

General- for Lake Nancy (and all lakes not owned by a single person or with an area in excess of 1 acre), herbicide use requires a licensed applicator and aquatic permit by the NYSDEC.  They require little local labor, and can last from one to several growing seasons, depending on numerous factors, such as extent of control, effect on non-target plants, reinfestation of target plants, flow through rate, etc.. Both systemic (affecting metabolic or growing processes within most of all of the plant) and contact (affecting only what is contacting, usually through (plant) toxicity) herbicides are registered for use in NYS.  It should be noted that none of the herbicides available in NYS specifically (or at least selectively) target watershield or water lilies, and it is not known how significantly desirable native plants will be adversely affected by these herbicides.  Expected costs for a whole lake treatment would be approximately $15,000, while treatment of select shorelines or individual properties would be much less expensive.  It is generally more difficult to get NYSDEC permits for control of native plants, such as watershield and water lilies, since the impacts associated with these plants are more often localized rather than lakewide.

Herbicides Most Likely to Be Effective:

Aquathol and Hydrothol - Aquathol and Hydrothol are formulations of Endothal, a contact herbicide that inhibits protein synthesis.  The labels for these products identify watershield and white water lily as target plant species, although it is reasonable to expect that nearly every plant in treated areas will be adversely affected by the herbicidal treatment. It begins to remove target plants within treated areas within 1-4 days, and breaks down relatively quickly; however, this may contribute to a short-term oxygen deficit in treated areas.  It works best in water temperatures (>65°F) probably not found in Lake Nancy until later in the summer, and any lakewide treatment would probably be subject to the significant permitting scrutiny, due to the concern over water quality problems associated with rapid plant destruction and decay.  The literature suggests that it can be used for spot treatments, although these have not been well documented in New York State.  There is a one day swimming, three day fishing and seven day drinking and irrigation restriction on the use of the water. Expected costs for a whole lake treatment would probably be about $20,000-30,000, or about $400 to $700 per acre.

2,4-D- 2,4-D is a systemic herbicide.  2,4-D is absorbed in the leaves and causes abnormal growth in the plant tissues, eventually killing the plant; it can be applied in granular or liquid form, and usually takes 15-20 days to work.  The granular form is usually used for spot treatments, and the liquid form for whole lake treatments. The literature suggests it may be effective at controlling both watershield and the waterlilies.  There is a three week restriction on use of the water for drinking and irrigation after application, although since the treatments are best conducted in last spring, this might not affect lake use.  This herbicide cannot be used in lakes that serve as drinking water supplies.  Expected costs for a whole lake treatment would probably be about $15,000-25,000, or about $300 to $800 per acre.

Herbicides Less Likely to Be Effective

Diquat- Diquat is a contact herbicide.  It is absorbed into the leaf surface and eventually destroys cell membranes; it is applied in liquid form, and works within 15 days.  It also is used primarily for whole lake treatments.  It is not commonly used for control of watershield or water lilies. 

Sonar- Sonar works by preventing the production of carotenoids, which prevent sunlight from degrading the chlorophyll pigments in the plant stems, it can be applied in liquid or granular forms, and usually takes 15-45 days to control plants.  Since the chemical rapidly disperses in the water, it is not effectively used for spot treatments, although relatively new formulations of this herbicide have exhibited some success in spot treatments in other states (they have not been used in New York).  The literature indicates that watershield is not well controlled by Sonar, and the experience in New York State is that water lily control requires a dose high enough (greater than 15 ppb) that may also impact the low-lying plants, such as the native pondweeds and milfoils.  The required contact time for this herbicide (>30 days) may also not be easily met in Lake Nancy.

Rodeo, Copper Sulfate/Cutrine Plus- Rodeo is a formulation of glyphosate, an herbicide that inhibits protein synthesis.  It does not identify watershield as a target plant species, although the lilies are listed as targets.  Although copper sulfate and other copper products are often used to control algae and some larger plants, the required dose rates would be so high that other organisms would likely be affected.

C. BIOLOGICAL CONTROLS

General-although a variety of biological controls are presently available for controlling nuisance weeds, most of these, such as stocked herbivorous insects or plant pathogens, do not control watershield or the water lilies. The only available biological control for these plants is grass carp (specifically, the white amur), a sterile herbivorous fish that is stocked in lakes.  It is likely, despite the relative ease with which a permit was secured in 1999, that such a grass carp stocking would involve significant NYSDEC review and perhaps require the preparation of an Environmental Impact Statement (EIS) to evaluate the potential environmental impacts associated with the treatment.  In most parts of the state, this EIS needs to be prepared by a qualified biologist.

Much of the literature about grass carp suggests that watershield and water lilies are not among the preferred food for grass carp, particularly relative to the low-lying submergent plants in the lake.  While a high enough stocking rate would ultimately result in herbivorous control of these floating leaf plants, the carp would likely removal most to all of the submergent plants in the lake before making the great effort to pull the floating leaf plants into the lake. This would render the lake susceptible to invasive from other aquatic plants, and may at least temporarily result in the spread of the watershield and water lilies while the fish are consuming the low-lying plants.

There is also a concern that these plant tissues would be converted into nutrients, which could then trigger an algal bloom. While this does not appear to have occurred in the larger lake NYS applications (primarily in the Lower Hudson basin), these lakes are generally much deeper, with a much smaller overall plant biomass: water volume ratio.  While the low stocking rate and relatively rapid flow through time of the lake suggest that Lake Nancy is not susceptible to a post-stocking algal bloom, there is insufficient information about the algal-nutrient-macrophyte dynamics in Lake Nancy to provide assurances that this will not occur.  Grass carp generally do not feed well below 16°C, a temperature that may be exceeded in Lake Nancy only during three or four months of the year.  However, the literature does suggest that grass carp might acclimate to colder temperatures and alter their temperature feeding ranges.  Native fish populations might be adversely affected by any large-scale stocking of these fish.  The cost for stocking the lake, assuming vegetated cover to a depth of 10 feet and appx. 10-15 carp per vegetated acre would be about $7,000.  It is reasonable to expect multiple years of treatment, since the carp live for many years (the literature indicates a mortality rate (of a stable population) of < 5% per year).

Grass carp stocking requires the completion of an Environmental Impact Statement (EIS) and a permit from the DEC Region 5 office in Ray Brook.

SUMMARY

The summary of aquatic plant management strategies provided above indicate that no single comprehensive strategy (or at least one without uncertainty or potentially significant side effects) is available to control the periodic weed problem in Lake Nancy.  As in most lakes, the most effective plant management plan will involve utilizing multiple strategies to address short-term and long-term needs for all affected lake residents.  While “local” and “whole-lake” strategies, as defined above, should be considered, the advantages to local (shoreline) management appear to outweigh those associated with whole-lake plant management.  In addition, any long-term control of the weed problem in Lake Nancy, particularly along the shoreline and in the shallow coves, will require the reduction of sediment loading to lake, since it is likely that these materials helped to trigger the accelerated plant growth in these areas. Local residents should contact and work closely with the Saratoga County Soil and Water Conservation District to minimize the loading of sediment (and perhaps nutrients) to the nearshore areas of the lake, whether through overland flow or through the lake inlets.

It is likely that the most effective local strategies will be a combination of hand-pulling and benthic barriers.  Benthic barriers would be most effectively and efficiently employed to clear common swimming areas, and to clear vegetation from shared navigational channels (if these exist), since the former requires a small area of essentially vegetation-free bottom cover, and the latter requires at least the absence of surface or near-surface weed growth, neither of which can be assured by any of the long-term strategies, at least in the short term.  Hand-pulling would be most effectively utilized in areas where selective plant removal is required (such as a small patch of a nuisance plant in the midst of a larger, bottom dwelling, plant bed), although it would be less useful in dealing with nuisance levels of water lilies, since the required effort would be significant.

Given the nature of the weed problem (primarily floating leaf plants growing from the shoreline to a depth of about 8 feet, neither of which are preferred by grass carp), and the logistics of plant management on a lake with very limited ability (or desire) to launch large boats, site sludge dewatering sites, significantly drawdown the lake, and pay for very expensive lake management strategies, the most effective choices for whole-lake management appear to be limited to herbicides and shading, although large scale cutting operations would continue to make the lake usable even if the problem continues to escalate due to continual “re-seeding” from cut plants.  Neither herbicides nor shading have a long history of specifically targeting these plants in New York State, and both have downsides, including permitting issues, that might remove them from consideration.  Of the whole lake choices, the aquatic herbicides listed above are the most likely to control these plants in the treated areas, and spot treatments with these herbicides would be more likely to reduce the likelihood of undesirable impacts on non-target plants. However, herbicides have potentially the greatest “social” effect (even the suggestion to use herbicides will inevitably be controversial and elicit strong public response), and appear to be more expensive than most other plant management strategies.  If water can be retained in the lake for much of the spring and summer (unfortunately, the spring is often the most difficult time to maintain water levels), particularly if the lake can be drawn down early in the spring, then shading agents may be effective.  As noted above, however, the track record for shading agents in larger lakes is fairly limited, particularly in lakes with slight natural (brown) coloration such as Lake Nancy.  Any serious consideration of these agents should involve lengthy conversations with DEC Region 5 Pesticides staff.