Thanks to a “hands-on” kayak mission against invasive water chestnut this summer at Lake Taghkanic State Park, this popular lake ought to be clearer of these aquatic invaders for next paddling season.

And timing is critical in dealing with water chestnuts, floating plants which can rapidly spread to create dense patches that can clog a lake, damage the native ecosystem and make it hard for canoeists and kayakers to paddle.

Water chestnut (Trapa natans) is one of the several Aquatic Invasive Species (AIS) that are monitored in hopes of reducing abundances in state waterbodies. Widespread in the state, water chestnut is now found in 43 counties.

Invasive species, like water chestnuts, are organisms that are non-native to an area, typically causing harm to human health, the economy, and the environment. If left unchecked, AIS can spread quickly from one body of water to another, threatening biodiversity and potentially impeding recreational opportunities.

The key to battling the an infestation discovered this season at Lake Taghkanic in Columbia County was to remove hundreds of plants before going to seed. Water chestnuts are annuals, and thus must reseed themselves each year to propagate.

Anyone who has been out along a shoreline and came across a strong, spiny, star-shaped brown nut-like “fruit” or seed pods has found a water chestnut nut. Bearing four sharp spines or points, each nut contains a single seed that can produce 10 to 15 stems.

Anchored to the water bottom, the plants have submerged, feathery brownish leaves on stems that can grow up to 15 feet long. On the water’s surface, these stems come to an end with a floating rosette, or circular arrangement of leaves. The leaves are triangular shaped with toothed edges.

These clusters can float on the surface due to buoyancy bladders connected to the leaf stems, forming dense floating mats that can be nearly impenetrable. Each rosette produces about 20 of the hard nut-like fruits in the late summer and early fall which, after dropping from the plant to the water bottom, lay in sediment over the winter to sprout in the spring

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You can imagine the concern when water chestnut showed up in Lake Taghkanic State Park, a park focused on boating, swimming, water sports and beach activities. Controlling water chestnut at the park was vital to support these recreational opportunities as well as the native fauna of the lake, including one rare species known there.

Due to the fast-growing nature of water chestnut, it is important to control newly introduced infestations as soon as possible, also known as “early detection, rapid response” (EDRR). If left unchecked, patches of water chestnuts can spread prolifically.

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Water chestnut is an invasive species of high concern for many waterbodies in New York State, having potential ecological, economic and health impacts. The plant can form dense mats on the water’s surface, greatly impacting the organisms below. These layered mats can block sun and oxygen from submerged plants, resulting in a die back of native species and fish populations. Recreation is also inhibited by dense patches of water chestnuts, making it difficult to swim, boat, kayak, or fish. The spiny nuts often drift to shore, creating an additional hazard for pets and people to step on.

Effective control of water chestnut depends largely on preventing seed formation. By manually removing the plants in mid-summer before mature seeds can drop, managers can halt such potential reproduction.

At Lake Taghkanic, staff from the Office of Parks, Recreation and Historical Preservation, state Department of Environmental Protection, and Capital Region Partnership for Regional Invasive Species Management (PRISM) worked to rapidly respond to the infestation. This team of ten individuals were well-versed in the control of invasive species, and several team members had prior experience manually removing water chestnut.

Held July 16, the pull was led by Matt Brincka (NYS Parks Invasive Biologist), with other participants including Falon Neske (NYS Parks), Lindsey DeLuna (NYS Parks), Lauren Gallagher (NYS Parks), Rebecca Ferry (NYS Parks), Kristopher Williams (Capital Region PRISM), Lauren Mercier (PRISM), Lauren Henderson (PRISM), Steven Pearson (DEC), and Catherine McGlynn (DEC).

The team navigated to the water chestnut infestation in kayaks, maintaining social distancing and wearing face coverings when necessary. When manually pulling water chestnut plants, it’s important to reach as far down the stem as possible to pull the root system from the bottom sediment.

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Once pulled, the water chestnuts were collected in garbage bags, drained, and weighed. Within a day, more than 100 pounds, or from 300 to 400 plants were removed! The information was recorded for upload to iMapInvasives so that the infestation of water chestnuts can be tracked.

Afterward, the team also surveyed the 3.7 mile lakeshore to ensure there were no other visible water chestnuts. Parks staff developed a control plan that will include monitoring and hand-pulling at Lake Taghkanic annually in order to deplete the seed bank (seeds can remain viable for several years at the bottom) and keep the problem at bay.

Over the years, NY State Parks has organized and participated in several invasive species pulls, additionally having a seasonally staffed AIS Strike Team and Boat Steward program. Reader more about these programs in the posts below.

Selkirk Shores State Park has been one focus area for State Parks staff in efforts to control a water chestnut infestation. In 2015, about 240 bags of water chestnut were removed there, visibly reducing the biomass by 40 percent. During the 2016 season, another 12.5 tons were pulled out. This removal resulted in a decrease in abundance of water chestnut during from 2017 through this year, further maintaining the value of this State Park.

Prompt invasive species responses, such as water chestnut pulls, work towards ensuring recreational enjoyment and preserving natural ecosystems in our parks. Early detections of invasive species are often reported by patrons.

The next paddling season may be months away, but remember: If you believe you have found a new population of an invasive species at a State Park, tell a park staff member or reporting it in iMapInvasives will ensure that swift eradication action is taken.

Cover shot: Members of the removal team spread out in kayaks on Lake Taghkanic.

Post by Lauren Gallagher, State Parks Water Quality Unit