Boat users and other member of the public are being asked to avoid contact with “a high-impact” invasive water lily that has taken over a scenic bay in Lough Leane, the largest of the Killarney lakes.
The National Parks and Wildlife Service has confirmed the plant’s presence on the lakes and has asked that precautions be taken to avoid its spread.
The spectacular, bright yellow-flowered “fringed water lily”, or nymphoides peltata, was first identified in the Killarney lake in 2016.
Local boatmen said it seemed to have been eradicated at one point but has returned with vigour this year around Bog Island, in the bay alongside Ross Castle.
“If you try and go through it, it is impossible to get out,” one local boatman said of the plant, calling for the public to be made aware of the nature of the species, which can spread very rapidly.
The water lily thrives on shallow and nutrient-rich waters such as in the area around Ross Bay, into which the treated waters from the Killarney waste water treatment plant are discharged.
It is not the only invasive species to affect the area, with purple rhododendron having taken over much of the woodlands, including the oakwoods of the Killarney National Park.
As with rhododendron ponticum, nymphoides peltata will crowd out native species, including plants, insects and fish life, experts warn.
The dense weed was introduced by the horticultural industry. In Northern Ireland, where it has been of concern for some time, an information leaflet describes it as “very aggressive” and says it pushes out native species and prevents swimming and boating on ponds and lakes.
“Thick floating mats have prevented fishing, boating, swimming and other activities in a ponds and lakes,” according to a warning notice issued by the North’s environmental agencies.
As the invader pushes out native algae, the entire food web of lakes and ponds is disrupted, it says.
In Killarney, the spread of the weed is already proving problematic by getting stuck in boat engines. The National Parks and Wildlife Service (NPWS) is advising boat users not to drive through the mat of vegetation as this could lead to the weed being carried to other areas of the lake system.
Permits are required for boat use in the waters in Killarney. In addition, there is a requirement to wash boats and craft, the NPWS said in a statement.
“As with [for] all species of concern, the NPWS is always trying to find ways to eliminate the impact. With regards to this species the NPWS is looking to carry out trials to see what is the best method of control,” the agency said.