Curly-leaved waterweed (Lagarosiphon major) is an invasive species of plant that originates from southern Africa. It was probably introduced to Ireland as an ornamental species that escaped from a garden pond or that was discarded by an aquarium owner. This problem is not unique to Ireland, with Lagarosiphon major invasions common in many countries where it has been introduced.
Rapidly spreading with few natural enemies
Invasive species are non-native species that are introduced outside of their natural range and compete with native species. They can proliferate aggressively when conditions are favourable.
Lagarosiphon major was first discovered in Lough Corrib in 2005 and over the following three years spread rapidly to cover approximately 92 hectares of the lake. In response to this, a research and control project (CAISIE Project – 2009 to 2013) began in an attempt to lessen its impact on the lake’s ecosystem.
The CAISIE Project developed the weed control measures currently used on the lake, including mechanical harvesting and hand removal by scuba divers. One of the most innovative and successful methods employed was the use of biodegradable jute matting to cover the weed and kill it by starving it of light.
Lough Corrib is the largest lake in the Republic of Ireland and presents a significant challenge for the removal and/or control of this aggressive invader. The LARC project aims to build on the success of the earlier CAISIE Project by testing new technologies to find and map Lagarosiphon major. We also attempted to answer important questions, such as:
- Why does it grow in some areas and not others?
- What environmental conditions favour and limit its spread?
LARC tested a range of technical mapping solutions, including the use of underwater remotely operated vehicles (ROVs), sonar/hydroacoustic technology, unmanned aerial vehicles (UAV’s) and satellite imagery.