Invasive species are a hot topic lately — from zebra mussels to the emerald ash borer to black swallow-wort — and now the threat of another invasive aquatic plant species is a reality for wetlands in Braddock Bay.
If you have never seen water chestnut before, you might miss it because the plant floats on top of the water and blends in with lily pads. However, upon closer inspection, this invasive plant species has a distinct form in that the floating rosettes are waxy, triangular and toothed. Originally native to Europe, Asia and Africa, the water chestnut (Trapa natans) was introduced to the Cambridge Botanical Garden in Massachusetts sometime before 1879. Since that initial introduction, water chestnut has spread to Quebec and tributaries of the Niagara River and Lake Ontario in New York state.
Beneath the rosette, there is a distinct bladder-shaped petiole that is filled with air and spongy tissue. The really scary thing about these plants is that their stems form a complex root system that ends with the four-barbed fruit, which resembles a dangerous mace — and these fruit are sharp too, causing injury to peoples’ feet. On the surface, water chestnut’s rosettes can each produce 15 to 20 seeds, and these seeds, which mature to form the fruit, can likewise produce 10 to 15 rosettes. Population growth of this plant is explosive, and dangerous for native plant and aquatic animal communities.
Photo: Jamestown Audubon/flickr
See those barbs? I can only imagine how much those would hurt!
When they mature, water chestnut rosettes form dense, continuous mats over the surfaces of lakes and slower moving waters such as wetlands. These mats can choke out other plant species and can hamper the movement of personal watercraft and fishing boats. Another important negative impact of this invasive species is that it reduces dissolved oxygen levels in the water column. The dense mats on the water’s surface block out sunlight to the plants in the deeper waters, causing a decrease in photosynthesis. The bottom stem and underwater modified leaves carry out photosynthesis, but large volumes of decomposing plant material literally consumes the oxygen out of the water. This in turn leads to anoxic conditions, which are not suitable to fish and invertebrate species.
So, what can we do to prevent the further spread of aquatic invasive plant species?
The NY DEC has a five word slogan that sums
up how we can help mitigate the water chestnut and other plants and animal species from traveling from one body of water to the next: check, clean, drain, dry, and disinfect. If you have a small boat or own a pair of fishing waders, check the exteriors for obvious signs of invasive species. Motorized boats provide many attachment sites such as the propeller, axles, rollers, and fishing lures, that can become tangled with water chestnut. After checking your boat, it is necessary to clean off any mud or vegetation present, since the mud could contain viable roots and seeds. Let’s try to stop the spread of this invasive plant before it takes over other coastal wetlands!