BFS Technical Report # 24

Trapa natans: Invasions and Effects and

Water Chestnut (Trapa natans L.) in an Oneonta, NY Wetland

Submitted to:

NYS Power Authority

WILLARD N. HARMAN MATTHEW F. ALBRIGHT

WILLOW EYRES

SUNY ONEONTA BIOLOGICAL FIELD STATION

5838 ST HWY 80 COOPERSTOWN, NY 13326

March 2007

INTRODUCTION

Exotic species introductions have extensively influenced biological communities worldwide. A variety of aquatic invasive plant species, in particular, have become nuisance infestations in many locations, disturbing ecosystems, displacing native species and interfering with water uses. This paper discusses the problems associated with aquatic invasive plants as well as the biological and ecological aspects of invasion using Trapa natans L. (water chestnut) as a template. The history of its invasion and establishment in the northeastern United States was traced through a review of available literature. The plant’s biological and ecological characteristics were studied to give insight to the debilitating effects of aquatic invaders on water ecosystems, such as the alteration of geomorphology, water chemistry, macroinvertebrate communities, and stand structure of native species. Specific sites of invasion were analyzed, which included the Hudson River Basin, the Chesapeake Bay Watershed, the Great Lakes Region and Southern New England.

BIOLOGY OF Trapa natans

Water chestnut (Trapa natans) is an aggressive annual aquatic plant native to Europe, Asia and the northern countries of Africa (Ding and Blossey 2005). The plants was once thought to belong to the Trapaceae family, however modern molecular research puts Trapa under Lythraceae in the order Myrtales (Stevens 2001). It grows best in shallow, nutrient rich lakes, rivers and ponds and is generally found in waters with a pH range of 6.7 to 8.2 and alkalinity of 12 to 128 mg/L of calcium carbonate (Naylor, 2003).

Water chestnut is a dicotyledonous herb with a floating rosette of leaves around a central stem. Species exhibiting rosettes respond to water movements and buoyant tissues in the stem, and leaves maintain stability on the surface of the water. The spongy inflated leaf petioles of T. natans also help the rosette to float. Many aquatic rosette species have a leaf mosaic with a wide range of leaves that develop on arenchymatous petioles; Trapa demonstrates this mosaic (Figure 1) (Groth et al. 1996). The leaves of floating plants are forced to physiologically deal with being exposed to air and water simultaneously. Carbon dioxide and oxygen move through stoma in the upper epidermis. Floating leaves will usually take a circular peltate form (Sculthorpe 1967). The lamina (the expanded part of the leaf) of T. natans is rhombic in shape and is toothed toward the tip of the leaf (Naylor 2003). The leaves have little or no lignin and the vascular tissues are generally poorly developed in the leaves (Sculthorpe 1967). The upper stem swelling has a lacunate pith and four or five rings of air spaces in the cortex whereas the remaining pith is compact having only two rings of cortical lacunae in the lower stem (Naylor 2003).

The inconspicuous flowers are found on the leaf axils of younger leaves above the water. The meristem elongates and produces new leaves as it grows so that the older leaves and developing fruit are further down the stem and underwater (Sculthorpe 1967). The single seeded mature fruit are woody and bear four sharply pointed horns. Water chestnuts begin to flower in early June and the nuts will mature approximately a month

later. Flower and seed production continue into the fall until the first frost kills the rosettes. When mature, the fruits fall from the plant and sink to the bottom of the body of water. Seed dormancy can be from four months to twelve years. The horns may act as anchors to limit movement of the seed, thus keeping them at suitable water depths (Naylor 2003). Winter survival of the nuts generates the bed of Trapa at that site the following year. A small fraction of nuts are also carried on buoyant, detached floating ramets (a clonal offshoot) allowing the nuts to be dispersed to downstream sites (Groth et al. 1996).

Water chestnut has adventitious roots that develop in pairs on either side of the leaf scars at lower nodes of the floating stem. The roots are feathery and can often reach to the sediment, but usually remain suspended in the water column (Groth et al. 1996). The roots also contain chlorophyll which has often misled people to think they were submerged leaves with segments comparable to the terrestrial roots of such species as Bergia capensis or Heteranthera zosteraefolia (Sculthorpe 1967). Some oxygen reaches the internal tissues of the roots by diffusing in solution along the epidermal gradient but oxygen also diffuses from photosynthetic sites. There is a system of cortical lacunae for diffusion (Sculthorpe 1967). Like many other aquatic plants, Trapa has no primary root system, just the adventitious roots that extend from the hypocotyls (the primary organ of plant extension). The lateral roots contain only one strand of xylem and phloem. Although the most important function of the roots is to absorb nutrients, they also provide an anchor for plant, but the developmental origin of the roots is unclear (Groth et al. 1996).

Aquatic annuals are quite unique in that a large number of them propagate clonally, whereas most terrestrial annuals do not. In an annual species, clonal growth multiplies the opportunities of an individual for sexual reproduction without producing overlapping generations of ramets. The explosive growth of this exotic plant may be due to several phenomena. There is some evidence that this species behaves as a perennial in parts of North America, and the rapid expansion of populations of the plant may be due to the proliferation of clonal fragments that subsequently proliferate the following year. The increase may also be via an increase in the rate of seed production. Typically, in this species, only one seed within the nut develops, but it may be that under low density conditions, two seeds develop. It is also possible that phenotypic plasticity allows it to develop more flowers per rosette, or more flowers may successfully develop into nuts, at low density (Groth et al. 1996).

Typically a Trapa plant is capable of producing three primary ramets and they develop in a specific order. The first ramet arises from the center of the nut; the second develops on the side opposite the hypocotyls, and the third between the first shoot and the hypocotyls (Groth et al. 1996).

Figure 1. The distinguishing rosette (1), nut (2), leaflet showing buoyancy bladder (3) and root stalk with filiform rootlets (4) of T. natans. Modified from http://aquat1.ifas.ufl.edu/tranatdr.jpg

DISTRIBUTION

Water chestnut is native to the warm temperate regions of Eurasia and North Africa. There is some discrepancy in the literature as to which decade Trapa natans first entered the U.S., and when it established. Naylor (2003) states water chestnut was first recorded in North America near Concord, Massachusetts in 1859. Hummel and Findlay (2006) state that it was first introduced to the U.S. in 1875, while Pemberton (1999) states it was first observed in 1884, growing in Sanders Lake, Schenectady, New York.

Populations have become established in many locations in the northeastern United States, including the Hudson River, Lake Champlain, Oneida Lake and six of its tributaries, the Nashu River in New Hampshire and the Connecticut River in Connecticut. In the United States it has been documented in Connecticut, Delaware, New York, Maryland, Massachusetts, New Hampshire, Vermont, Virginia, and Pennsylvania (Pemberton 1999) (Figure 2).

Trapa also thrives in the Great Lakes Basin. In 1998, water chestnut was found in the South River in Quebec, which is connected to the Lake Champlain outlet via the Richelieu River. Its spread has continued because of the suitability of habitat. In 2001, Trapa was found in the Pike River, which flows into Mississquoi Bay (Pemberton 1999).

Figure 2. Distribution of Trapa natans in the US (2004).

Source: http://www.anr.state.vt.us/dec/waterq/lakes/images/ans/lp_wc-usamap.gif

VECTORS OF INVASION AND DISPERSAL

Water chestnut was introduced into the wild sometime before 1879 by a gardener at the Cambridge Botanical Garden in Cambridge, Massachusetts. The gardener reported planting it in several ponds. It was also introduced in Concord, Massachusetts, where it was planted in a pond adjacent to the Sudbury River. By the turn of the century, it proliferated in the pond and the river. Since then, water chestnut has spread to other states and other river and estuary systems (Naylor 2003). Ballast waters also offered an easy means for Trapa nuts to gain entrance to America (Mills et al. 1996). Water chestnut has also become naturalized in Australia as well (Heywood 1993).

Hellquist (1997) believes that, once introduced, Trapa is dispersed primarily by ducks and geese, but it is unlikely that the nuts could be carried over long distances. Although observations have been made of Canada geese with Trapa fruits attached to their feathers, the size and weight of the propagules make it unlikely they would remain attached during prolonged flight. Because Trapa fruits fall to the bottom of lakes and rivers, there is a low probability of getting tangled in plumage. It has also been

determined that muskrat eat Trapa fruits and many also facilitate their dispersal (Les et.al. 1999).

Trapa is also believed to be a determined “hitchhiker”, which accounts for its dispersal from the Hudson River to Lake Champlain on boats (clinging to ropes and nets) using the barge canal (Countryman 1970). Wind and wave action disperse plant pieces and fruits locally. Trapa fruits have long been consumed by humans and were sold by street vendors in western New York State from about 1925 to 1935. Canned Trapa fruits are sold in gourmet food shops and plants are still being cultivated for the edible nuts, however most tinned “water chestnuts” are in fact Cyprus esculentus (Les et al. 1999). The Trapa fruit contains much starch and fat, and are a staple food in eastern Asia, Malaysia, and India (Heywood 1993).

INFESTATION IMPACTS ON HUMANS

The impacts of a water chestnut invasion are not only devastating ecologically, but also negatively affect humans. In most areas the biggest problem has become the interference of water chestnut in recreational and economic uses of navigable waters. Dense mat and root systems can completely cover the surface of the water, preventing swimming and canoeing and tangling in propellers of motor boats. In addition, the spiny seeds of the chestnut have been known to cause harmful injury to bathers and beach users. Similarly to infestations of Eurasian water milfoil (Myriophyllum spicatum), the mats are favorable sites for mosquito breeding. Water chestnut also affects the aesthetic value of an area. The plant is likely to be regarded as unattractive in large quantities and can be unsightly when washed ashore. Recreational fishing is also affected as many fish populations tend to avoid the infested areas because normal biological processes are terminated or severely reduced (NEMESIS 2005)

Economically, efforts to reduce plant population sizes and stop its spreading have been costly. In the Chesapeake Bay region alone, $2.8 million have been spent in the past 20 years for mechanical harvesting, herbicide applications and hand pulling and monitoring programs (NEMESIS 2005).

Because of the nuisance of water chestnut and other aquatic invasives, more precautions are being taken and more legislation being created. For example, many states have created strict legislation to require permits for all water withdrawals and water transports to prevent the spread of any invasive plants. Bulk water transporters that offer such services as filling swimming pools, hydroseeding, irrigation, spraying for dust control and roadbed compaction at construction sites, and similar activities often withdraw water from rivers or lakes at convenient access points. Many states now require pipes, hoses and tanks of trucks to be inspected and thoroughly cleaned (Mills 1996).

CHESAPEAKE BAY WATERSHED

A distinct feature, and one of the Chesapeake Bay’s vital natural resources, is the beds of submerged aquatic plants that inhabit the shallow water areas. In addition to its high primary productivity, this vegetation is significant because it is a food source for waterfowl, a habitat and nursery for many species, a shoreline control system and a

nutrient buffer. However, over the past 50 years, there have been several distinct periods in which significant changes occurred within the submergent aquatic vegetation. These ecological changes began with the Zostera marina wasting disease in the 1930s and Myriophyllum spicatum and Trapa natans proliferation in the 1950s. These two periods in effect caused widespread changes in the vegetation populations during the 1960’s and 70’s (Orth et al. 1984).

Within the Chesapeake Bay watershed, water chestnut first appeared in 1923, on the Potomac River near Washington D.C. as a two acre patch. The plant spread rapidly, covering 40 miles of river in just a few years. By 1933, 10,000 acres of dense beds extended from D.C. to Quantico, Virginia. Water chestnut was first recorded in the Bird River in Baltimore County for the first time in 1955 (Orth et al. 1984). The Maryland Department of Game and Inland Fish and Tidewater Fisheries used mechanical removal and an herbicide (2,4-D, the only fully licensed herbicide successfully used against water chestnut) to control it. However, in 1964 it reappeared in the Bird River and an additional 100 acres were discovered in the Sassafras River in Kent County, of which 30 acres were mechanically removed. This effort was highly successful as no plants were reported in surveys until 1997 when a water chestnut population was again discovered in the Bird River (Naylor 2003).

The infestation spread from approximately 50 plants in the summer of 1997 to over three acres in 1998, demonstrating the explosive propagation ability of Trapa natans. This population increased again into the Sassafras River and a substantial mechanical and volunteer harvesting effort began on both rivers in 1999, resulting in the removal of almost 400,000 pounds of plants from the two rivers. This undertaking was successful but researchers realized that viable nuts still remain in the sediments and that continuous follow-up measures will be necessary (Naylor 2003).

HUDSON RIVER BASIN

The Hudson River Basin drains parts of five states (New York, New Jersey, Massachusetts, Connecticut and Vermont) as well as six physiographic regions (the Canadian Shield, the Folded Appalachians, the Catskills, the Hudson Highlands, the New England Upland, and the New Jersey Lowland). A study by Mills et al. (1996) found there to be 113 exotic species in the fresh waters of the Hudson River basin, of which Trapa natans was listed. In fact, the study placed water chestnut third on the list (after Potomogeton crispus and Rorripa nasturtium) of plant species to have had the most significant ecological impacts on the basin. In the Hudson River Basin, water chestnut is typically found in low energy environments in lakes and rivers, especially in the freshwater tidal sections. The authors suggest that in many regions, alterations of the environment through cultural eutrophication, siltation, and hydrological modifications only contributed to the success of Trapa, as well as many other invasive species in the basin such as Myriophyllum spicatum and Lythrum salicaria (Mills et al. 1996).

Most of the exotic plants were first reported in the Hudson River Basin in the 19th century. Several vectors brought in large numbers of exotics. Plants, in particular, originated chiefly as escapees from cultivation or in the solid ballast of ships. The high number of exotics in the Hudson River is probably due to the long history of human

commerce throughout the region. Therefore, this human activity has influenced the number of species in the Hudson River Basin and has strongly influenced the kinds of species that are present (Mills et al. 1996).

In the Hudson River, from the Tappan Zee Bridge to Troy, water chestnut covers approximately 2% of the water’s surface. Bed sizes range from 12m2 to almost 100,000m2, with an average size of 1500m2. These numbers again demonstrate the explosive propagating capability of Trapa (Hummel and Findlay 2006).

A study by Hummel and Findlay (2006) analyzed the effects of water chestnut beds on water chemistry and therefore its detrimental effects on the Hudson River. Since under favorable conditions, Trapa is capable of covering almost 100% of the water’s surface, it often shades out submerged aquatic vegetation such as Vallisneria americana, Potamogeton perfoliatus and even the extremely invasive Myriophyllum spicatum. These dense beds also affect gas exchange, light penetration and invertebrate and fish populations. Water chestnut was also observed to be a source of dissolved organic carbon in the Hudson and Mohawk Rivers, which indicates that there is a direct correlation between rates of photosynthesis and increases in dissolved organic carbon (Hummel and Findlay 2006).

The effect of aquatic plants on water velocity has direct implications for transport of water column constituents such as particulate matter, plankton, and detritus. Because sedimentation, deposition increasing as flow decreases, water chestnut beds may enhance settling of suspended solids thus reducing turbidity and contributing to local accumulation of fine sediment (Pierterse and Murphy 1990). The presence of water chestnut and other vegetation can also affect flow in a channel of water in one or more of the following ways: (1) reducing water velocities, thus raising water levels. (2) raising the water table on adjacent lands causing waterlogged soils and leaching of nutrients, and (3) changing the magnitude and direction of currents, therefore increasing the risk of local erosion, and interfering with other water uses (navigation, recreation) (Pierterse and Murphy 1990). These detrimental effects can be seen in various sites in the Hudson River Basin.

The effects of large water chestnut beds on fish populations in the tidal freshwater Hudson River have also been studied. Fish species diversity is low under the beds, and the species with the largest populations are those that tolerate low dissolved oxygen content. Constant movement of fish into and out of the beds suggests water chestnut is not used continuously as protection from predators. The high plant surface area of the beds, however, provides habitat for various invertebrate species and significantly increases potential prey for fishes. Very large beds, however, reduce dissolved oxygen which negatively affects some fishes and invertebrates. Very large beds exert the greatest control on water quality and the two largest beds constitute 50% of the total Trapa coverage on the Hudson. Invertebrate and fish communities might gain from the separation of large beds into small disconnected beds so that they provide foraging habitat for fishes without creating the harmful effects of the large beds (Hummel and Findlay 2006).

THE GREAT LAKES REGION

During the historical development of the Great Lakes Basin, human activity has played a major role in the introduction of nonindigenous organisms into the world’s largest bodies of freshwater. Plants, in particular, had several vectors for reaching the Great Lakes. Mills et al. (1993) suggest that Trapa may have accidentally escaped from ornamental gardens or cultivation areas. Ballast water, however, is the vector most commonly thought to have brought water chestnut to the Great Lakes. Ballast was in use by the late1880’s and was being dumped into to the Great Lakes at that time. In 1875, work to enlarge the canals from the St. Lawrence River to Lake Superior began to allow it to accommodate a ship 79 meters long with a 13 meter beam. Even though these ships were not the massive boats seen in the St. Lawrence Seaway today, the ballast they brought into the Great Lakes was substantial. With the opening of the enlarged seaway system in June 1959, the amount of ballast water released into the lakes increased dramatically (Mills et al. 1993).

In many respects, the aquatic plant invasion history of the Great Lakes is similar to the nearby Hudson basin. Both regions have a large number of exotic vascular plants, fish and large invertebrates. Most are Eurasian in origin. Both areas can contribute the presence of exotic species to unintentional and deliberate releases. A large number of these species have had a significant ecological impact; however, the Hudson River received much higher numbers of exotic introductions in the 19th century, while the 20th century was the high point for introductions in the Great Lakes region. The primary reason for this is the timeline of settlement from east to west. Also the plant exchange between the Hudson and the Great lakes was not symmetrical. The Hudson River Basin received many more species from the American Interior Basin than the Great Lakes region did from the Atlantic Slope. This probably happened because the freshwater biota of the Atlantic Slope is much poorer than that of the American Interior Basin, so that when these two regions were connected by the Erie Canal and other human activities, the total movement of species was from the west to east (species-rich to species-poor) (Mills et al. 1996).

SOUTHERN NEW ENGLAND

The southern New England region includes the southernmost portions of Vermont and New Hampshire, the southeastern portions of New York, and all of Connecticut, Massachusetts and Rhode Island. Although the Chesapeake Bay Watershed and the Hudson River basin are partially included in this region and have been previously discussed, this perspective provides a good overview and a larger geographical scenario.

Non-indigenous aquatic species have persisted in Southern New England and their introduction continues. The number of aquatic plants has increased steadily in the region over the past 150 years, with no signs of slowing. Trapa natans is one of the earliest recorded non-indigenous plants in the region. According to Les et al. (1999), the earliest reliable record for water chestnut is sometime before 1879, in Middlesex County, Massachusetts with only five other species arriving earlier. Those species include Acorus calamus, Nasturtium officionale, Potamogeton crispus, Marsilea quadrifolia, and Callictriche stagnalis. Nearly all plant species have persisted and flourished in the region

and there is no sign that the introduction of other non-indigenous aquatics will diminish. Les et al. (1999) noted T. natans to be quite a nuisance weed in North America, but that it is extirpated or endangered in much of Europe. On the list of New England’s 10 major aquatic weeds (Steward 1990) Trapa natans is the only genus exclusively non-indigenous to North America. As many as 88% of the invasive aquatics probably first entered the country as cultivated plants, and nearly 76% of introduction cases are implicated by escapes (Les et al. 1999).

LAKE CHAMPLAIN, VERMONT

Although there is not much information on water chestnut in Lake Champlain, the available data can be used to consider the capabilities of water chestnuts to invade the Champlain Region and its extent of infestation. In Vermont, water chestnut occupies significant areas of southern Lake Champlain and extends over a range of 54 square miles (Figure 3). Six Lake Champlain tributaries support water chestnut populations. Five other lakes or ponds in Vermont have now been confirmed with water chestnut. Annual surveillance followed by hand pulling has kept water chestnut controlled in those waters. The plant was first introduced into the lake in the 1940’s. In 2001, water chestnut was found and hand pulled from the Lemon Fair River near Middlebury. Control efforts and research continue (Dick 2004).

Figure 3. Distribution of Trapa natans in Lake Champlain, VT.

Source: http://www.lcbp.org/atlas/HTML/is_chestnut.htm

EFFECTS ON ECOSYSTEM PROCESSES

Trapa natans and many other invasive aquatics can invade an area and severely alter an ecosystem. Wetlands, in particular, seem especially vulnerable to these invasions because they are landscape sinks, which accumulate debris, sediments, water and nutrients. Even though less than 6% of the earth’s land mass is wetland, 24% of the world’s most invasive plants are wetland species (Zedler et al. 2004). Wetland invaders contrast with many terrestrial invaders in that: seeds are often dispersed by water, plants and plant parts can be dispersed by flotation, and aerenchyma protects below ground plant tissues from flooding in anoxic soils and has the ability for rapid nutrient uptake, thus allowing for rapid growth (Zedler et al. 2004).

In wetlands, non-indigenous species abundance associates with road density, suggestive of that landscape position interacting with dispersal pathways and disturbances to help plant establishment. Wetlands fed by surface water from agricultural and urbanized watersheds usually have many invasive species. Wetlands that are not fed primarily by surface water have small watersheds, depending on other sources for their water supply like rainfall or groundwater. These wetlands are usually species rich and relatively free of invasive plants (Zedler et al. 2004).

There are many characteristics of wetlands that provide an area for opportunistic plant invaders such as: runoff, nutrient cycles, sediment composition, open standing water, human made structures, and salinity cycles. The characteristics that benefit an invasion by Trapa natans will be discussed in more detail. Floodwaters accumulate in wetlands, and anoxia becomes a cumbersome challenge for most species, except those that are flood tolerant. These species usually possess aerenchyma tissues or pressure ventilation. Plants with aerenchyma can also achieve high plant biomass, potentially growing very rapidly. Trapa stems contain aerenchyamtous tissues and therefore have that advantage. Trapa also has a great advantage in that its adventitious roots positively respond to changes in water depth and nutrient availability. Dense, floating rhizome mats provide another advantage for reasons discussed earlier (Orth et al. 2004).

Wetlands have shown to be significantly altered by plant invaders. Many invasive plants are unwanted because of the effects they have on habitat structure. Species that alter the physical structure of a site have high potential for shifting hydrological conditions and animal uses. Invasive plants are commonly understood to shrink both plant and animal diversity. As low species richness sometimes grants greater invisibility, the potential for positive feedback does exist (Zedler et al. 2004).

Invasive plants that differ from native species in biomass and productivity, tissue chemistry, morphology, or phenology, can alter soil nutrient dynamics. Invasive species can affect food webs in multiple ways, by altering the quantity and quality of food, by changing food supply, or by changing susceptibility to predators (Zedler et al. 2004).

Sedimentation is both a cause and effect of wetland invasions. Wetlands in which sediments are flowing in, invasive plants find canopy gaps and bare soils to colonize. Where sturdy invasive plants colonize stream banks, sediments accumulate and alter geomorphology. The outcomes are similar in both habitats in that the topography is simplified and this is detrimental to the recipient community’s ability to support diversity in vegetation. At the same time, sediments carry nutrients (especially phosphorous) that

cause eutrophication and more rapid growth of many invasive plants (Zedler et al. 2004). Overall, invasive species are reported to significantly alter geomorphologic processes by increasing erosion rates, increasing sedimentation rates, increase soil elevation, or impact the effective geometry or configuration of water channels (Gordon 1998).

Species that alter geomorphology are also likely to influence hydrological systems by altering hydrological cycling, altering water table depth, or altering surface flow patterns. Non-indigenous species with evapotranspiration rates higher than those of the native flora may significantly alter the water cycles. In a study by Gordon (1998), the author found that nitrogen-fixing invaders will alter biogeochemical cycles, effect soil nutrient availability and significantly alter water chemistry. This in turn will effect submerged vegetation and phytoplankton.

Aquatic macrophytes that form canopies also have their own set of effects on bodies of water. Extensive covers of floating plants, such as those produced by Trapa, shelter the surface from wind, reduce turbulence and aeration, restrict mixing and promote thermal stratification. Frodge (1990) hypothesized that the structure of the plant canopies are functionally important to variations in water quality and that in dense beds the canopies can vertically divide the water column. The study found that water quality differences and daily changes were strongly connected to the development of dense surface canopies. Significant differences in water temperature and dissolved oxygen were observed between the surface and the sub-canopy water. The low sub-canopy dissolved oxygen concentrations, and lack of daily change in dissolved oxygen, indicated a reduction of sub-canopy photosynthesis, even during daylight hours. The self-shading by macrophytes can, therefore, change the lower stem area to a site of oxygen demand rather than an area of oxygen surplus. However, the plant canopy effect appeared to be dependent on the size and geometry of the body of water. A deeper lake with a larger ratio of open water would be naturally buffered to the effects of the plant beds. The study even suggested that the areas above and below the canopies could be considered fundamentally different habitats (Frodge et al. 1990).

In eutrophic waters, aquatic macrophytes such as Trapa can grow vigorously and play a significant role in removing nutrients from polluted water. Floating leaved plants are characterized by a short life span, which results in high rates of biomass turnover. Nutrient availability has been described to affect the leaf life-span of terrestrial plants, and even thought there are small amounts of data for aquatic macrophytes; the same is hypothesized to be true. In a study by Tsuchiya (1993), the data showed that with increased nitrogen availability, net production of T. natans increased as well, concluding that growth may be restricted by nitrogen flux. The study also discussed Trapa’s ability to take up nitrogen from both the water and from the sediment (Tsuchiya 1993).

Yet another effect of Trapa on ecosystem processes is in the area of invertebrate communities. As mentioned before, water chestnut leaves release oxygen into the atmosphere while the stems and roots consume oxygen from the water, so beneath the large, dense beds the water may become hypoxic (low oxygen) or even anoxic (devoid of oxygen). Also, because Trapa has a different architecture than submerged plants, and depletes water of dissolved oxygen, it has been thought to support distinctive communities of macroinvertebrates and fish. In a study by Strayer et al. (2003), the authors compared the macroinvertebrate fauna associated with Trapa with those of the

nearby beds of Vallisneria, the species Trapa is thought to have displaced in the freshwater tidal Hudson River. Within the two habitats, they found that macroinvertebrate density was higher in Trapa than in Vallisneria, and higher in the interior of the Trapa beds than near the edges. As expected, the density of epiphytic macroinvertebrates was positively correlated with plant biomass. In contrast, the density of benthic macroinvertebrates was nearly unrelated to plant biomass. Epiphytic invertebrate communities on Trapa were distinct from those on Vallisneria, with the communities of Trapa characterized by Cricoptopus sp., Actinolaimus sp., Pristina leidyi, Nais variables, Sida crystallina and Ablabesmyia sp. (Strayer et al. 2003).

Similarly, benthic invertebrate communities differed significantly between the beds of the two macrophyte species. Species characteristic of the benthic habitats under Trapa included: Pyrrhalta nympheae, Dreissena polymorpha, Sida crystallina, and Gammarus tigrinus. In general, invertebrates were larger from Trapa than from Vallisneria and densities were higher in Trapa, but this was probably a result of high biomass in Trapa beds (Strayer et al. 2003).

METHODS AND ATTEMPS OF CONTROL

Biological control possibilities were investigated in the early 1990s. Surveys were conducted by the U.S. Department of Agriculture in 1992 and 1993 that sought natural enemies of water chestnut in Northeast Asia (Pemberton 1999). Galerucella birmanica, a beetle that consumes up to 40% of water chestnut leaf tissue, was found to have various other plant hosts, thereby making it unsuitable for bio-control purposes in the U.S. Other insects that fed exclusively on water chestnut were identified but were found to be non-damaging. Predators found in the warmer climate of India have potential but could not withstand the cooler temperatures of water chestnut-infested Northeast regions of the United States (Pemberton 1999).Other promising candidates include: Galerucella nymphaeae L., Nanophyes japonica Roelofs and Nanophyes sp.

Hand removal is an effective means for eradication of smaller populations

because water chestnut roots are easily uplifted. Their removal is important because floating plants can spread seeds downstream. The potential for water chestnut seeds to lay dormant for up to 12 years makes total eradication difficult. However, hand-harvesting from canoes and raking have been useful. Research has also attempted to hinder populations by manipulating water levels (Naylor 1999).

For large-scale control of water chestnut populations herbicides and mechanical

harvesting can be effective. Aquatic plant harvesting boats are often employed in instances where waterways are blocked. For example, mechanical harvesting in 1999 on the Sassafras River removed an estimated 260,000 pounds of water chestnut (Naylor 1999). Unfortunately, mechanical harvesting boats cannot operate in some of the shallow areas that water chestnut can inhabit. For this reason, mechanical harvesting has been complemented by hand harvesting in Maryland on the Bird and Sassafras rivers. Herbicide 2,4-D has been tested, and deemed safe for use by federal and state agencies. Used widely in the U.S., it has shown to be non-adverse on neighboring wildlife. Maryland and Virginia used 2,4-D in the 1960s to eradicate Eurasian water milfoil

populations in the Bay. Due to public perception, the use of herbicides is seen as a last resort option. Integrating all possible methods for water chestnut removal will be the most effective course for eradication (Naylor 1999). The best method for control, however, remains to be prevention. Programs in many areas have developed systems for boat cleaning and inspection to prevent the water chestnut, and other invasive species, from entering a water source altogether. This has proven to be effective with cooperation and much more economical. For example, the state of Maine began a courtesy boat inspection program in 2001 to reduce the risk of transporting invasive species via boats, trailers and equipment (Anon. 2005).

CONCLUSIONS

Elton (1950) stated in his book The Ecology of Invasions by Plants and Animals, “…quite a large number of species are able to achieve a worldwide distribution as it is, either because the ecological barriers that hold in others are not barriers to them, or because, which is partly the same thing, they have exceptionally good powers of dispersal (page 33).” Today, this “power of dispersal” is termed propagule pressure. The exact number of propagules necessary for Trapa natans or other invasive plants to establish is unknown; however, it has been determined by Lockwood et al. (2005) that increased pressure increases the probability of introduction and establishment of invasive species. This increase in pressure is a benefit due to increased genetic variability helping to overcome stochastic events, climate, or biotic interactions. The durability of the Trapa fruit and the plant’s tolerance for different habitats could imply that a relatively lower propagule pressure is needed for Trapa to establish.

Lockwood et al. (2005) also discussed the idea that disturbed locations, which could be experiencing physiological stress or resource flux for example, would lower the necessary propagule pressure. Our findings support this theory, as the Chesapeake Bay Basin, Lake Champlain Region, Southern New England, and especially the Hudson River Basin were quite disturbed by human influences by the time Trapa invaded throughout the 19th century. In all of these areas, there were also previous plant invaders that may have increased the ability of Trapa to invade, an idea also investigated by Lockwood et al. (2005).

The literary findings for this paper also show support for the “enemy release hypothesis”. This hypothesis poses that exotic species are successful because they have escaped the specialist herbivores and pathogens present in their native range (Levine et al. 2004). In its native range of Eurasia and northern Africa, Trapa does not grow and spread overwhelmingly and in some countries it is even threatened or endangered. For example, the species has been entered in the Red Data Books of Ukraine (1996) and Bulgaria (1984), and is protected in the Danube delta (Ukraine and Romania). This demonstrates that in these regions, water chestnut is very susceptible to herbivory, competition, pathogens and other factors.

In summary, several generalizations can be made about the water chestnut and its effects on the communities it invades. The unique morphology of the water chestnut roots, nuts and leaves give the plant a natural advantage by creating dense canopies that

shade out other competitors, in turn effecting nearly all aspects of a water habitat (for example, hydrological cycles, sedimentation, erosion, water chemistry and temperature). Flora and fauna are directly affected by these alterations. Research has demonstrated that many native fish and macroinvertebrate species, as well as native macrophytes, are significantly affected, as are mammals and amphibious organisms. The quick dispersal and growth rates of the water chestnut make it difficult to control and even more difficult to eradicate, although efforts to do so via hand pulling, mechanical, and herbicides have proved effective but are costly, time consuming and labor intensive. Many habitats may benefit from dividing up large beds of Trapa to mitigate some negative effects. Efforts should be aimed at keeping the water chestnut populations in the northeastern US (and out of large rivers such as the Ohio, Mississippi and Susquehanna Rivers) and limiting its abundance there, as its spread into other lakes and rivers could lead to larger infestations in other states and regions. The ability of Trapa natans to tolerate a wide range of habitats, grow fast and produce durable nuts makes it such a successful invader.

REFERENCES

Anon. 2005. Maine Courtesy Boat Inspections. Maine Department of Environmental Protection. [Online]. http://www.maine.gov/dep/blwq/topic/invasives/inspect.htm

Countryman, W.M. 1970. The history, spread and present distribution of some immigrant

aquatic weeds in New England. Hyacinth Control Journal 8(2): 50-52. Dick, T.J. 2004. Water Chestnuts: Aquatic Exotic Animals and Plants. [Online].

http://www.iisgcp.org/EXOTICSP/waterchestnut.htm. Ding, J. and B. Blossey. 2005. Impact of the native lily leaf beetle, Galerucella nymphaeae (Coleoptera: Chrysomelidae), attacking introduced water chestnut, Trapa natans, in the northeast United States. Environ. Entomol. 34(3):683-689. Elton, Charles. 1958. The Ecology of Invasions by Plants and Animals. John Wiley and

Sons, New York. Frodge, J.D. and G.L. Thomas, and G.B. Pauley. 1990. Effects of canopy formation by

floating and submergent aquatic macrophytes on the water of two shallow Pacific Northwest lakes. Aquatic Botany 38: 231-248.

Gordon, D.R. 1998. Effects of invasive, non-indigenous plant species on ecosystem

processes: Lessons from Florida. Ecological Applications 8(4): 975-989. Groth, A.T, L.L. Doust, and J.L. Doust. 1996. Population density and module

demography in Trapa natans, and annual, clonal aquatic macrophyte. American Journal of Botany 83(11): 1406-1415.

Hellquist, C.B.. 1997. A guide to invasive non-native aquatic plants in Massachusetts.

Massachusetts Department of Environmental Management, Boston, MA.

Heywood, V.H. 1993. Flowering plants of the world. Oxford University Press, New

York. Hummel, M. and S. Findlay. 2006. Effects of water chestnut (T. natans) beds on water

chemistry and in the tidal freshwater Hudson River. Hydrobiologia 559: 169-181. Levine, J.M., P.B. Adler, and S.G. Yelenik. 2004. A meta-analysis of biotic resistance to

exotic plant invasions. Ecology Letters 7: 975-989. Les, D.H. and L.J. Merhoff. 1999. Introductions of non-indigenous aquatic vascular

plants in southern New England: a historical perspective. Biological Invasions 1: 281-300.

Lockwood, J.L., P. Cassey, and T. Blackburn. 2005. The role of propagule pressure in

explaining species invasions. Trends in Evolution Ecology 20 (5): 223-228. Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor. 1993. Exotic species in the Great

lakes: A history of biotic crises and anthropogenic introductions. Journal of Great Lakes Restoration 19(1): 1-54.

Mills, E.L, D.L. Strayer, M.D. Scheuerell, J.T. Carlton. 1996. Exotic species in the

Hudson River Basin: A history of invasions and introductions. Estuaries 19(4): 814-823.

Naylor, M. 2003. Water chestnut in the Chesapeake Bay Watershed: A Regional

Management Plan. Maryland Department of Natural Resources. NEMESIS: National Exotic Marine and Estuarine Species Information Systems. 2005.

Trapa natans. [Online]. http://invasions.si.edu/nemesis/CH-IMP.jsp?Species_name=Trapa+natans

Orth, R.J. and K.A. Moore. 1984. Distribution and abundance of submerged aquatic

vegetation in Chesapeake Bay: An Historical Perspective. Estuaries 7(4): 531-540.

Pierterse, A.H. and K.J. Murphy. 1990. Aquatic weeds: The ecology and management of

nuisance aquatic vegetation. Oxford University Press, New York. Pemberton, R.W. 1999. Water Chestnut. Invasive Plant Research Laboratory, US

Department of Agriculture, Florida. Sculthorpe, C.D. 1967. The biology of aquatic vascular plants. Edward Arnold Publishers

Ltd., London.

Stevens, P.F. 2001. Angiosperm Phylogeny Website. Version 6, May 2005 [and more or less continuously updated since].

Steward. K. 1990. Aquatic weed problems and management in the eastern United States.

In: Piertarse and Murphy (eds) Aquatic Weeds: The ecology and management of nuisance aquatic vegetation, 391-405. Oxford University Press, Oxford.

Strayer, D.L., C. Lutz, H.M. Malcom, K. Munger and W.H. Shaw. 2003. Invertebrate

communities associated with a native and an alien macrophyte in a large river. Freshwater Biology 48: 1938-1949.

Takayoshi, T. and T. Iwakuma. 1993. Growth and leaf life-span of a floating-leaved

plant, Trapa natans L., as influenced by nitrogen flux. Aquatic Botany 46: 317-324.

Trapa natans L. 2007. National Wetlands Inventory: US Department of Agriculture.

[Online]. http://plants.usda.gov/java/profile?symbol=TRNA Zedler, J.B. and S. Kercher. 2004. Causes and consequences of invasive plants in

wetlands: Opportunities, opportunists, and outcomes. Critical Reviews in Plant Sciences 23(5): 431-452.

Water Chestnut (Trapa natans L.) in Oneonta, NY Wetland End of Year Summary Report January 2007 For: New York State Power Authority c/o Julius Fuks From: SUNY Oneonta Biological Field Station Project Advisor: Dr. Bill Harman Project Coordinator: Matt Albright Graduate Student Research: Willow Eyres Property Owner: Louis Blasetti Research Objectives

The objectives of this project are to eliminate water chestnut in a wetland draining into the Susquehanna River near Oneonta, Otsego County, NY as well as to ascertain nutrient export from this wetland as a result of control activities and to study the impacts on non-target aquatic submergent vegetation. Background Currently, there are only three known populations of the invasive Trapa natans in the Susquehanna River Basin. One small population inhabits Goodyear Lake, in which ongoing hand pulling efforts may be effective. Another population inhabits Cincinnatus Lake, while the third inhabits a 40 acre wetland near Oneonta. The area is privately owned by Mr. Louis Blasseti. The water chestnut population was first observed five years ago and has since grown to approximately two acres in size, crowding out other previously dominant aquatic plant species: Ceratophyllum demersum, Potamogeton crispus, Elodea canadensis, and Lemna minor. There is concern over the adverse effects that water chestnut could have in the Susquehanna drainage basin. An incident of water chestnut introduction into the Chesapeake Bay region demonstrates its invasive and dominating abilities in the waters of the Mid-Atlantic States. During one year in a reach of the Sassafras River (Kent County, Maryland) the water chestnut population grew from about 50 plants to 1000s covering over three acres of surface water. There, it caused major changes in water circulation, temperature, light penetration, native plant populations, as well as navigation and recreation (Naylor 2003). Management plans for the water chestnut included hand-pulling efforts as well as several applications of the herbicide 2,4-D. After several years of continued control, the region has begun to recover (Naylor 2003). In an effort to prevent further dispersion of this Oneonta water chestnut population, it was thought best by project advisors to use a chemical weed killer. In past years, hand-pulling efforts were ineffective. Monies from the New York Power Authority, the Millennium Pipeline Company and a legislative grant from the NYS

Senate were donated and used to purchase a quantity of the herbicide 2,4-D and to develop a work plan. The herbicide was applied by the Allied Biological Company on 26 August 26 2006. All necessary permits were issued by the Department of Environmental Conservation. 2,4-D is an herbicide that is toxic to broad leafed plants but less harmful to grasses. The formulation used is a butoxyethyl ester of 2,4-D, also termed Aqua-Kleen® by Cerezagri-Nisso. Aqua-Kleen® has been used successfully for selective control of noxious aquatic plants including water milfoil, coontail, spatterdock and water stargrass for more than two decades (Aqua-Kleen 2005). Known as a hormone weed killer, the herbicide is an aryloxyalkanoic acid or a “phenoxy herbicide”. These chemicals have complex plant interactions resembling those of auxins (growth hormones). Once absorbed, 2,4-D is translocated within the plant and accumulates at the growing points of roots and shoots where it inhibits growth. This herbicide has low soil absorption, a relatively short half-life and a high potential for leachability. Aqua-Kleen® can be used in specific areas without impacting untreated areas of the lake or water body. While some formulations of 2,4-D are highly toxic to fish, the compounds used for this project are not (Aqua-Kleen 2005). Aquatic invertebrates do not in general seem to be sensitive to the herbicide and toxicity to birds is low (Dow 2006). Experimental Approach Water depths were first recorded in effort to develop a bathymetric map (see Appendix 1). (Currently, the pond is not shown on state or county maps). Delineation lines and GPS points were also documented to define the limits of open water. My preliminary work at the wetland began with a survey of the dominant aquatic and wetland plant species: identifications, collections of voucher samples, and preparation of herbarium specimens. Appendix 2 provides a list of plant species found. Water samples have been taken at the deepest part of the area of open water as well as at the outlet monthly (see Appendix 3). To show the effects of the herbicide on biomass and distribution of both the water chestnut and non-target plants, a “Rake Toss Procedure” developed by Cornell University was performed with the help of the SUNY Oneonta Biological Field Station summer interns. The work involved tossing a double sided rake 9m from the boat and dragging in the aquatic plants, then quantifying each species using predetermined categories. Dry weights have been documented for each category, and approximate biomasses have been established (Lord and Johnson 2006). Appendix 4 provides the raw rake toss data collected on 16 June 06. Using Delorme™ software and aerial maps obtained from National Resource Conservation Service (NRCS), the distribution and biomass of the aquatic plants will be mapped and used for comparing subsequent years. Appendix 5 is a 2004 aerial map of the site. During the growing season of 2007, the numbers will be compared to elucidate the effectiveness of the herbicide on the chestnut, determine effects on non-target plant species and water quality. We have hopes of greatly diminishing the population, thereby reducing propagule pressure downstream in the river.

As expected after the first application, the herbicide worked quickly on the water chestnut, with evidence of brown leaves within two weeks. Plants began to fragment and sink in the water column. Root hairs turned brown. Additional members of the water chestnut population in the lake were removed during a two day hand-pulling effort later that summer, coordinated by the Otsego County Conservation Association. However, the chestnut showed regrowth after approximately one month, sprouting new shoots. These new plants did not reach maturity and drop seeds before the growing season ended. The herbicide probably would have been more effective if applied earlier in the summer, therefore we are concerned that the original population may have dropped some seed. Permit restraints, however, hindered a more timely application. We plan, based on the chestnut population size in the spring and available money, a second herbicide application in 2007.

Water quality and analysis documents concentrations of all nutrient fractions in

May and June abruptly decreasing in early July. This correlates with the record flood conditions experienced in late June, which may have purged nutrient rich waters from the system. We will be watching closely in the spring of 2008 in an attempt to develop further explanations for variations in nutrient concentrations

Many hectares of wetlands are chemically treated annually to control exotic plants

in New York State. Does control of large populations of ecologically dominant plants release significantly large amounts of nutrients into aquatic systems already stressed by eutrophication? Given the potential for federal regulation of nutrient loading (via total maximum daily loads [TMDL’s]) in the Susquehanna Drainage Basin in the near future, how important are such considerations to agencies implementing large plant control programs in the region. My work and analysis of water quality information will begin to give insight into the importance of these concerns.

REFERENCES Aqua-Kleen. 2005. Cerexagri: Aquatic habitat management. [Online]. Accessed 14 Nov

2006. http://www.cerexagri.com/aquatic/aquakleen.asp Herbicide 2,4-D. 2006. Dow AgroSciences LLC. [Online]. Accessed 28 Oct 2006.

http://www.dowagro.com/ca/prod/frontline-2.htm Lord, P. H. and R. L. Johnson. 2006. Point Intercept Rake Toss Relative Abundance

Method. Cornell University Research Ponds. Naylor, M. 2003. Water Chestnut in the Chesapeake Bay Watershed: A Regional

Management Plan. Maryland Department of Natural Resources.

Appendix 1. Blasetti Wetland Water Depths Oneonta, NY

FIG. Various water depths (cm) Elevation: 1,066 feet Scale: 2.5cm= 500 feet 18T 049 Easting 469 Northing

90

90 70

170

60 60

60

90

120

70

70 90

100 70

↑ N

Appendix 2. Wetland and Aquatic Plants Species(** indicates dominant species) Alnus incana Brassenia schreberi Carex sp. Ceratophyllum demersum** Cicuta bulbifera Cornus ammomum Dryopteris sp. Elodea canadensis** Impatiens capensis Juncus effusus Lemna minor** Lysimachia nummularia Lythrum salicaria** Lysimachia quadrifolia Onoclea sensibilis** Polygonum amphibium** Potamogeton crispus** Potamogeton natans Potamogeton pectinatus Rumex verticillatum Sagittaria latifolia Solanum dulcamara Spirodela polyrhiza Spyrogira sp.** Symplocarpus foetidus Thelypteris sp. Trapa natans** Typha latifolia** Wolffia colombiana W. borealis Appendix 3. Ammonia, nitrite+nitrate, total nitrogen and total phosphorus concentrations, 2007. Ammonia NO3 + NO2 Total Nitrogen Total Phosphorus mg/l mg/l mg/l ug/l 22-May 0.793 2.330 8.620 2510.0 30-May 0.614 3.060 11.500 2950.0 15-Jun 0.641 2.390 8.190 2410.0 10-Jul 0.004 0.160 0.635 38.8 21-Jul 0.010 0.140 0.637 33.4 22-Aug 0.084 0.010 0.621 79.5 3-Sep 0.028 0.010 0.409 25.3 3-Sep OUTLET 0.089 0.008 0.468 46.4 15 Sep DEEP 0.051 0.013 0.401 37.2 15 Sep OUTLET 0.086 0.008 0.426 34.7

Appendix 4. Plant rake data, 16 June 06.

Appendix 4 (cont.). Plant rake data, 16 June 06.

Appendix 4 (cont.). Plant rake data, 16 June 06 (cont.).

Appendix 5.