Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Non-indigenous and cryptogenic charophytes (Characeae) forming meadows in the Shannon River, Ireland.

Abstract

The Starry Stonewort (Nitellopsis obtusa) occurs as a perennial charophyte forming localized meadows in Lough Derg, and in a downstream reservoir, on the Shannon catchment in Ireland. It was recovered from depths 2-5 m. In shallower water it occurs with aquatic angiosperms. A single plant was recovered from deep water in the mid-region of Lough Derg and entire plants were present in a public harbour in the northern part of Lough Derg. Its status in Ireland is unclear. It is unlikely to have been overlooked in the past, so may have been introduced. Collections appear to be of a female clone reproducing by means of its distinctive star-shaped bulbils and plant fragments. While pale green oogonia were obtained no red mature stages developed and no antheridia were found. The fine branches of N. obtusa acted as a collector of the Zebra Mussel (Dreissena polymorpha). The invasive Nitella mucronata var. gracillima was distributed close to, and within, public boating harbours in Lough Derg and at one locality formed a meadow where it is likely to have persisted for over a decade.