By Brianne Ledda
Monica Matt found a few rocks and leafy strands of Eurasian watermilfoil at the bottom of Lake Ronkonkoma early on Saturday, April 27, but not the hydrilla tubers she was looking for.
A lake management graduate student at SUNY Oneonta, Matt is building a water management plan for the lake. She was testing the waters to see if hydrilla took up residence again this year.
“[Hydrilla is] one of the top scarys of New York State,” Matt said. “It’s not yet established everywhere in the state, and Ronkonkoma is one of the big places on the island that [the Department of Environmental Conservation (DEC) is] scared it might be the source for more spread throughout the state.”
Eurasian watermilfoil and hydrilla are invasive species; they’re not native to the ecosystem, and they’re usually harmful to other species. They also often reproduce quickly, in ways that are difficult to control.
“[Hydrilla has] these tubers, that kind of act as storage sacs, that are viable for quite some time,” Luke Gervase, the education and outreach coordinator at Long Island Invasive Species Management Area (LIISMA PRISM), said. He also pointed out that hydrilla and Eurasian watermilfoil can reproduce through fragmentation – if one little piece breaks off, it can grow into an entirely new plant.
Invasive species are a huge threat to Long Island water bodies, according to Suffolk County’s Water and Land Invasive Species Advisory Board. They outcompete native species and reduce biodiversity. These intruders have put approximately 42 percent of threatened or endangered species at risk, according to the National Wildlife Federation, and the Reduce Risks from Invasive Species Coalition claims that they annually cause $127 billion in damage to the U.S. economy.
“Some [invasive species] come over here accidentally and they just take off because they’re very vigorous,” Brian Smith, the Vice President of the Long Island Native Plants Initiative, said. “They don’t have necessarily predators to keep their members in check or eliminate them altogether. So we’re kind of being attacked on all sides, whether it’s a plant, a new pathogen or insect.”
Scientists and government agencies like the DEC often step in to prevent invasives from spreading or growing out of control. Matt, who’s coordinating with the local DEC in Suffolk County, is thinking about establishing a population of grass carp – a type of invasive, plant-eating fish – in Lake Ronkonkoma, to keep invasive plant populations in check.
“Some species, like hydrilla, especially when they start growing in abundance – and you get acres and acres and acres of these plants – you really have to try to bring in a professional to try and manage the species,” Alejandro Reyes, an aquatic ecologist and lake management consultant said. He added that for some species, like water chestnut, volunteer efforts to help with management are preferred, though not in extreme cases.
The South Shore Estuary, which stretches over 70 miles across both Nassau and Suffolk counties and struggles with water chestnut and ludwigia, might be considered an extreme example. Aquatic plants will grow so fast and so thick that native species don’t have a shot at survival, Christie Pfoertner, the science and outreach coordinator from the estuary reserve, said
“It can get so bad where you have an entire pond in a freshwater area that’s covered in all [plants] so people can’t even kayak or boat, or do any kind of recreation because you just can’t get through to the water,” Pfoertner said.
Volunteer efforts, often organized by the DEC, fuel periodic plant pulls, where volunteers set out in canoes or kayaks to physically remove invasive plants floating in the water. The DEC has at least four planned on Long Island in July.
“We invite the public out to do pulls – we hand them a kayak or they go out on one of our little boats and just try to get as much out as possible,” Kyle Jones, a fisheries and wildlife technician from the DEC Fisheries, said.
The best way to protect native ecosystems from harmful invasives, however, is by keeping them out of water bodies in the first place, Carrie Brown-Lima, the director at the New York Invasive Species Research Institute, said. Suffolk County has a “do not sell” list that ban harmful invasives, and people are advised to clean their boats and fishing gear before switching between bodies of water.
“Prevention is the best policy,” Brown-Lima said. “Once an invasive species becomes established in a water body, it’s really hard to get rid of it. The more effort we put into prevention, the more bang you get for your buck.
Early detection is the strategy that Yuriy Litvinenko, an ecologist who usually works with terrestrial invasive plants in the Connetquot River State Park Preserve, is using to take care of a sprouting watercress crop. He was doing work for another project when he noticed the plant growing in a few of the pools by the park’s river.
“It’s very easy to control when it’s small,” Litvinenko said. “You can literally just pluck it. It doesn’t seem to have really progressed to an awful extensive level yet, but yeah, a plan needs to be made.”
Scientists warn, however, to be careful to distinguish between invasive species and native species that are just a nuisance.
“A lot of people might complain about different things that are growing to a higher degree but are indigenous, versus when an invasive species comes in,” Kim Tetrault, a community aquaculture specialist with the Cornell Cooperative Extension, said. “What happens normally is that it kind of capitalizes on the environment because it either doesn’t have natural predators yet or it just is really liking what it’s finding and it blooms really quickly, and outcompetes natural stocks.”
Invasive species aren’t always terrible for larger water systems either, Bill Pfeiffer, a member of the Lake Ronkonkoma advisory board and a citizen scientist who’s been researching the lake with the DEC for the past eight years, said. He compared Lake Ronkonkoma to a big bowl of mud; historically, it’s been devoid of plants. The hydrilla in the lake provides structure for both predators and prey, and adds oxygen to the water.
He pointed out though that in other cases, there can be a lot of problems when invasives start to crop up, especially in smaller, more nutrient-rich, bodies of water.
“If you’re trying to swim or boat in there, you’d find it almost impossible to move through the water,” Pfeiffer said. “They create a big negative recreational impact and also because of the fact that they’re rafting on the surface, so now they knock out all of the sunlight. Anything underwater that needs light to survive isn’t getting what it needs.”