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Project Background Biological and Geological Heritage The Irish Geological Heritage (IGH) programme, run by the Geological Survey of Ireland (GSI) and National Parks and Wildlife, is aiming to identify, document, and protect geological heritage in the Republic of Ireland. Warm springs are a significant component of the groundwater theme (IGH16) of this programme. For an introduction to warm spring geology please click here. Thermal springs are also included for designation and protection based on their geological importance under the Natural Heritage Area (NHA) selection criteria and complimentary ecological descriptions of these sites would be most valuable. New ecological data on warm springs is also important both in the context of the Heritage Council Plan (2001-2005) and the National Biodiversity Action Plan (Dúchas 2002) and could also be a valuable addition and readily integrated into the IGH scheme. The presence of rare species in warm spring habitats has important implications for Irish biodiversity. Calcareous springs with tufa formation are recognised as the EU Annex I priority habitat ‘petrifying springs with tufa formation (Cratoneurion) (7220) and are included in the Heritage Council’s ‘Guide to Habitats in Ireland (Fossitt, 2000). The current survey also noted whether tufa was present or absent at the warm springs being examined. While providing new and valuable scientific data on the fauna, flora and habitats present in Irish warm spring, the project aims to promote public awareness, interest and knowledge in Ireland’s geological and biological heritage through the publication of results and the development of a website. Project data will provide new information that will be readily integrated into any national list of species compiled in accordance with the Convention on Biological Diversity and should provide a valuable input into Volume II of the Habitats Guide to Ireland – Invertebrates. It should be noted that monitoring of spring-dwelling organisms is suggested as a practical method of assessing groundwater quality and the history of individual aquifers (Biological Survey of Canada, 1990). The value of new data Springs occur at a point of discharge of groundwater at the surface and therefore tend toward a uniform temperature. This temperature is normally the mean annual air temperature of the region but may be altered by geothermal processes (Hynes, 1970). Springs may discharge directly into the channel of a stream (rheocrene), or it may discharge into a small basin or pond which overflows into a channel (limnocrene). Springs, seepages and spring wells are ubiquitous in Ireland. Many wells and springs are today regarded as holy places and some sites, named after saints, reflect the older pagan respect for springs in the Irish landscape. Although cold spring are common features, warm springs or wells are rare. Normal groundwater temperature in Ireland varies from 9.5oC to 10.5oC - warm springs are considered as having appreciably higher temperatures than ‘normal’ for at least a part of the year. Ireland is not a geothermal active area and thus very hot springs do not occur. It is generally accepted in the literature that a spring whose temperature was not reliably recorded at more than 12oC at some time could not be called ‘warm’ (Aldwell and Burdon, 1980). Such a low range warm spring would feel cool in the summer and slightly warm in the winter. Warm springs are easily recognisable without any temperature measurement equipment on a cold winter’s morning when frost will have melted away in the vicinity of the feature and underground warm water streams feeding the springs will be traced as lines of thawed frost along the surface. The recorded history of warm springs The oldest recorded warm spring in Ireland is located at Mallow, Co. Cork. In 1757 Rutty (from Bristol Spa in England) stated “Mallow water was first discovered and introduced into practice by Dr. Rogers of Cork about the year 1724” (Aldwell and Burdon, 1980). The mallow warm spring is one of a number of springs that rise naturally in an area that is known locally as Spa Glen. However two of the best known warm springs in Ireland were brought to the surface through anthropogenic activities.Louisa Bridge spring at Leixlip, Co. Kildare came to light during the construction of the Royal Canal in 1794 and Kilbrook spring near Enfield, Co. Meath was discovered when gravel quarrying was carried out during railway construction in the 1890’s. Until the mid 1960’s only two warm springs were recognised in Leinster. Granger and Davies (1965) added a third spring to the list by rejuvenating interest in St Gorman’s, a warm spring visited by Du Noyer in 1859 but thereafter forgotten by investigators. Since then several additional warm springs have been recorded in Leinster. Aldwell and Burdon (1980) recorded a total of 17 warm springs (including boreholes) in Ireland, 14 being located in Leinster, the remaining 3 in Munster. In 1982 a project to investigate the “Geothermal Energy Potential of Ireland” (Minerex, 1983) resulted in the addition of four springs in Leinster and three in Munster to the list of sites that showed signs of geothermal activity influencing groundwater temperature. The Geothermal Energy Potential of Ireland project is the only comprehensive work undertaken to date that has catalogued the hydrogeology of all warm spring features in Ireland. A total of 29 warm springs are now known to issue at the surface in the Republic of Ireland. Warm springs: ecological and biological significance Springs have their own distinctive invertebrate fauna, comprising a small suite of stenotopic (able to tolerate only a narrow range of environmental conditions) invertebrates that are at least partially subterranean. Several organisms are true cavernicoles (cave dwelling species), lacking eyes and body pigment. However, a number of other invertebrates associated with springs are also frequently encountered in seepages and other associated habitats and lack specialised adaptations to subterranean life. An interesting feature of springs is the occurrence of relict species in addition to certain invertebrates that are restricted to spring sources (crenobionts) For example Apatania muliebris is an Arctic relict trichopteran that maintains an Arctic lifecycle in Irish springs in the summer months when warm air temperatures do not impact on comparatively low spring water temperatures. Post-glacial warm relicts have also been found in Ireland which seek refuge in warm springs owing to comparatively high winter temperatures e.g. Agapetus fuscipes and Wormaldia occipitalis (Nielson, 1950; in Thorne, 1998). Some members of the groundwater fauna are also found in springs. In Ireland, the only known hypogeans are two species of Niphargus, the well shrimp Niphargus kochianus irlandicus and Niphargus wexfordensis (Gledhill and Holmes, 1994), both found in Irish springs (Reynolds, 1998). The fauna of isolated springs can provide a unique insight into endemism and zoogeography and are also habitats where some relict species of former times have endured, protected from large oscillations in climate (Hynes 1970). A spring is, as Odum (1971) stated, "the aquatic ecologist's natural constant temperature laboratory because of the relative constancy of the chemical composition, velocity of water and temperature." Some collections from Irish springs exist (Davies and Hill, 1966; Grainger and Davies, 1966 and Fahy, 1975) however; these collections are limited to few sites. Compared with other aquatic habitats, the biological characteristics of Irish springs are still are relatively unknown. Fauna of Irish springs (cold and warm) and project taxonomic coverage A number of factors should be considered in examining the invertebrate community of springs. Firstly, spring habitats tend to be relatively nutrient rich in comparison with surface waters (influenced by surrounding land) because of substantial leaching from direct contact with bedrock. It should also be noted that, despite a typically low volume of flow, springs features are generally derived from very extensive underground aquifers and are therefore not greatly affected by short term fluctuations in rainfall. The fauna of hard water springs has been found to primarily consist of crustaceans, with insects dominating more acidic soft water springs (Glazier, 1991). Glazier suggests that the adverse effect of low pH and alkalinity on crustaceans and molluscs may be one explanation for their absence from soft water springs. Crustaceans and molluscs are important in cold hard water springs as their non-emergent lifestyle means they can take full advantage of the flow constancy and the absence of large predators in these environments. Non-emergent taxa can also take better advantage of the year round opportunity for growth and reproduction than species with extra fluvial life stages that would be exposed to potentially fatal winter temperatures. Distribution studies of spring invertebrates have found that insects are more abundant downstream of the source while crustaceans dominate the region of the springhead (Glazier, 1991). The constancy of flow rate and temperature in springs may encourage the maintenance of dense macrophyte assemblages. Macrophytes that are characteristic of temperate hard water springs enhance macroinvertebrate abundance by supplying refuges from any water current present and by increasing the surface area for attachment and by trapping large collections of detrital food particles.
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© Ecological Consultancy Services Ltd 2003 |
Descriptions
of thermal springs in Ireland have been limited
(Fahy, 1975). The vast majority of ecological data collected on warm
springs are now very dated. Current, up to date information is urgently
required on these unique environments which are under increasing threat
from groundwater abstractions and pollution. Existing ecological information provides valuable insights into
the conservation importance of warm springs, however, other than an
unpublished undergraduate thesis (Thorne, 1998), these habitats have not
been surveyed in any comprehensive and structured way for
macroinvertebrates or macrophytes since the mid 1970’s (Fahy 1975). Even
then this detailed study was limited to only one site at Kilbrook,
Enfield, Co. Meath. This project aims to compile a dataset of detailed
information on macroinvertebrate and macrophyte community structure for
a number of Irish warm springs.