Knocksouna Spring. Kilmallock, Co. Limerick.

Survey site description 

The Knocksouna warm spring group was discovered by the Geological Survey of Ireland in January, 1982. Knocksouna is one of a number of springs that issue at the surface in this area. The physical form of the spring has been largely left unchanged even though it is located at the bottom of a relatively steep river valley on land used for intensive dairy farming and is located directly below a large farm enclosure area. Warm spring water discharges directly into the River Loobagh which runs in a westerly direction approximately 10 m south of the spring. The substratum in the spring is composed of a layer of organic mud overlying a hard limestone gravel bottom. An average surface area for this spring was approximately 600 m2. The spring has been investigated for it's potential use in aquaculture in the past.

Macroinvertebrate / faunal survey 

Knocksouna spring was sampled during all three seasonal visits. Ninety individual specimens from 8 species / higher taxa were recorded during spring sampling. The gastropod Bithynia tentaculata was the most abundant organism and dominated the fauna on this occasion (representing 80% of the total sample). Notably low numbers of Asellus aquaticus (14) were recorded. The remaining fauna comprised small numbers or solitary specimens of oligochaete worms, leeches, molluscs and coleoptera (Hygrobia hermani). The summer survey revealed a richer fauna (24 species/higher taxa), and slightly elevated numbers of individuals. Bithynia tentaculata were again the most abundant species. Other fauna recorded in small numbers were seed shrimp - Ostracoda indet., the midge larvae Chironomidae indet., coleopteran larvae and adults and water bugs (Gerris lacustris). Other fauna such as leeches, the snail Lymnaea peregra, the mayfly Cloeon simile, and the beetles Dysticidae and Colyembetinae, were recorded in small numbers or as solitary specimens. Species richness and abundance decreased substantially in autumn with 23 individuals from 6 species / higher taxa being recorded. Beetle larvae (Haliplus sp.) were the most abundant organisms, while Bithynia tentaculata and B. leachi formed a substantial portion of the fauna. Other organisms were recorded as one or two individuals and included Asellus aquaticus, gastropod, Planorbis planorbis, the beetle Hyphdryus ovatus and oligochaete worms.

Physico-chemistry 

Water temperature ranged from 15.2 (spring) to 16.2oC (summer), pH ranged from 7.3 (autumn) to 7.68 (spring), conductivity levels were similar on all surveys (467-8 µS/cm) and oxygen concentrations ranged between 1.6 mg/l and 16% saturation (summer) to 2.8 mg/l and 30% saturation (spring).

Aquatic macrophyte survey 

Knocksouna spring exhibited the second highest plant species richness recorded in this survey. Between ten and eleven species were recorded from the spring. Most species were recorded on all three visits. Abundant species included water cress - Rorippa microphylla and water plantain - Alisma plantago. All other species were recorded as occasional or rare including the algae Cladophora sp., the charophyte species C. vulgaris, and Nitella sp., the bryophyte Riccia fluitans, and the vascular plants Apium nodiflorum, Callitriche obtusangula, Iris pseudacorus, Juncus bulbosa, Lemna trisulca, Lemna minor, Typha latifolia, Veronica catenata and Zanichellia palustris. Water levels in the spring did not fluctuate greatly, however macrophytic and algal growth increased towards autumn.

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