Errit Lough
Errit Lough is a freshwater lake in the west of Ireland. It is located in west County Roscommon in the catchment of the Boyle River. The lake is a Natura 2000 site. It is protected as a List of [Special Areas of Conservation in the Republic of Ireland#Roscommon|Special Area of Conservation] since May 2016 under the qualification of a specific habitat type: the presence of ‘Hard Water Lakes’, alternatively known as ‘Hard oligo-mesotrophic waters with benthic vegetation of Chara spp.’
Location
Errit Lough is located approximately 10 km south-west of the town of Ballaghaderreen in County Roscommon. The lake is situated in the upper part of the Boyle River catchment. The area of Errit Lough included in the SAC designation is located in the townlands of Cloondart, Derreenamackaun, Errit, Gortaganny and Tully in County Roscommon. Schedule 1 of the Statutory Instrument for this site identifies it as encompassing an area of 84.59 ha.SAC qualification
The Errit Lough site was proposed as a Site of Community Importance in 1998. In 2016, the site was designated as a Special Area of Conservation, with site code IE0000607. Statutory Instrument 266 of 2016 established the site as an SAC. The feature which qualifies this site for SAC status is the presence of Hard Water Lakes – this habitat is also known as ‘‘Hard oligo-mesotrophic waters with benthic vegetation of Chara spp.’. Under the EU Habitats Directive, this is an Annex I habitat type. The Interpretation Manual of European Union Habitats defines this habitat as comprising:“Lakes and pools with waters fairly rich in dissolved bases or with mostly blue to greenish, very clear, waters poor in nutrients, base-rich . The bottom of these unpolluted water bodies are covered with charophyte, Chara and Nitella, algal carpets. In the Boreal region this habitat type includes small calcareous-rich oligo-mesotrophic gyttja pools with dense Chara carpets, often surrounded by various eutrophic fens and pine bogs.”
Hard water lakes are typically base-rich, oligotrophic and unpolluted, with clear water. The NPWS publication "Benthic vegetation in Irish marl lakes: monitoring habitat 3140 condition 2011 to 2018" notes that the alkalinity of this lake was 136 mg/l CaCO3 and the euphotic depth was 3.3 m. Typically lakes with total phosphorus of less than 0.01 mg/l have euphotic depth of over 5.0 m, but Lough Errit, a high-colour lake, has low levels of phosphorus and a low euphotic depth. This document notes four Charophyte species occurring in this lake, with charophyte cover of 0.52. It is noted that in Ireland, marl lakes and cut-over bogs often occur in the same location, an issue for this habitat type is the leaching of coloured water into these lakes, resulting in a high water colour. This may explain the low levels of deeper water vegetation in Errit Lough.
Vegetation
The east side of this marl lake has exposed stony shores. On the west side of the lake are more sheltered areas. Within these more protected bays can be found emergent species such as Common Club-rush and Common Reed. Bottle Sedge and Common Spike-rush also occur on the west side of the site.As part of the designation criteria for the site, there are beds of stonewort species growing on the lake bed. These species include Chara pedunculata, C. rudis, C. desmacantha and C. fragilis. In certain areas of the lake, floating Yellow water-lily are recorded.
Nearby Special Areas of Conservation and proposed Natural Heritage Areas
As can be seen from the National Parks and Wildlife Service designated sites map, other designated SAC sites nearby include Urlaur Lough, Derrinea bog, Carrowbehy/Caher Bog, Drumalough Bog, and the River Moy SAC. This concentration of designated SACs in the area indicates that this location is ecologically very valuable.The Errit Lough site has been included as a proposed Natural Heritage Area by the National Parks and Wildlife Service. Other nearby pNHA sites include Urlaur Lough, Carrowbehy/Caher Bog, Derrinea Bog, Mannin And Island Lakes, Drumalough Bog and Lough Glinn.