Vegetation (Floating River Vegetation) - Office of Public Works

prevented aquatic growth.
Water levels in the River Nore survey square were low and often absent for many of the
smaller watercourses surveyed. In watercourses with water depth described as a trickle the fine sand
or mud deposits of the river bed were too dry to support floating river vegetation. Deeper waters
were dominated with larger pondweed species.
Floating river vegetation was observed on the majority of the survey sites within the
Mulkear River square. Stone, gravel and fine sand were the dominant channel substrate recorded.
Shade and partial shade were noted for site 1 and site 8. Floating river vegetation was observed on
all sites maintained by the Office of Public Works along with two channels not maintained by the
Office of Public Works.
Watercourses within the River Maigue survey square consisted of mud and fine sands and
were often heavily colonised by aquatic vegetation including floating river vegetation. Of the
watercourses surveyed over fifty percent were maintained by the Office of Public Works with site 2
supporting floating river vegetation. Site 3 was the only site to experience shade. It did not support
floating river vegetation.
Not all of the watercourses maintained by the Office of Public Works supported floating
river vegetation. Partial shade may be responsible for the absence of floating river vegetation at site
8 while low water levels on the River Feale may also be a factor. Stone and peat base was the
dominant substrate in the River Feale survey square supporting floating river vegetation.
Only four watercourses survey in the Bandon River square supported floating river
vegetation. Although partial shade was recorded for the remaining watercourses colonisation with
dense aquatic vegetation and terrestrial plant species reduced the sunlight penetrating the water
surface. The bed of the Bandon River at Dunmanway supported a sizeable population of floating
river vegetation.
3.6 Groenlandia densa on the back drains of the River Shannon
Groenlandia densa (Opposite leaved pondweed) is a legally protected plant species
classified as endangered and vulnerable in the Irish Red Data Book (Curtis & McGough, 1988).
Originally recorded at thirty-two sites across the republic of Ireland, sites in recent times the
number has decreased to a total of three sites in counties Limerick, Laois and Dublin. Groenlandia
densa (G.densa) colonises deposited mud on the bottom of ditches, streams, ponds and canals. It
has been suggested that the decline of the species in Ireland is due to land drainage and reclamation,
pollution, peat run-off and loss of habitat due to infilling of watercourses.
According to the EUNIS website four candidate Special Areas of Conservation (cSAC) in
Ireland have identified G. densa as part of their protected flora and these are tabulated below. Of
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