Southwest Ireland Research Articles

Vegetation change during the Mesolithic and Neolithic on the Mizen Peninsula, Co. Cork, south-west Ireland

Despite being rich in later prehistoric and historic archaeology that includes megalithic monuments, Bronze age copper mines and medieval castles, the Mizen Peninsula, south-west Ireland, has revealed little about its stone age past. Evidence for a Mesolithic presence in SW Ireland is rare and, to date, all archaeological finds of this age in Co. Cork are further north and east of the Mizen Peninsula. However a recent palaeoecological study of pollen, non-pollen palynomorph, plant macrofossil and microscopic charcoal data from a peat bog located near Mount Gabriel has provided evidence for disturbances, characterised by fire disturbance of woodland and exploitation of wetlands, since ca. 8400 years b.p. Two working hypotheses are considered to explain these disturbances: human activity or natural agencies. If the human activity hypothesis is accepted, they represent the first possible evidence of a Mesolithic presence on the Mizen Peninsula.

The role of glacitectonic rafting and comminution in the production of subglacial tills: examples from southwest Ireland and Antarctica

Sedimentological and structural geological data from two sites in southwest Ireland and Antarctica provide evidence for the formation of subglacial till by the brecciation and crushing of bedrock rafts. Up‐sequence transitions, from undisturbed bedrock, to deformed bedrock, to crushed and brecciated bedrock, to massive matrix‐supported till with far‐travelled erratics, represent a process‐form continuum of till production. Initially, bedrock fragments and rafts up to several metres in length are liberated from the substrate by glacitectonic thrusting and plucking. These rafts are then crushed to produce the matrix of a till. Such products are commonly referred to as comminution tills, although the original definition focused primarily on the second phase of the process (crushing of bedrock rafts and fragments) as well as abrasion of bedrock. Data from Ireland and Antarctica indicate that rafting of bedrock is an essential part of the process of till formation. This process is facilitated by weak sedimentary bedrock, which can be displaced along joints and bedding planes to form rafts that are then incorporated into the ‘proto‐till’ prior to being crushed subglacially. Our field data suggest that bedrock failure and displacement of such rafts can occur to depths of 3 m. The occurrence of erratics in the uppermost part of the till demonstrates that the glacier effectively mixes far‐travelled and local materials.

Epiphytes of Sitka spruce (Picea sitchensis) plantations in Ireland and the effects of open spaces

The epiphytes of the trunks and branches of mature Sitka spruce (Picea sitchensis) trees were studied in twelve plantations containing open spaces (glades, rides and roads) in the east and southwest of Ireland. A pair of trees was studied at each site: one tree at the south-facing edge of an open space and one in the forest interior. Spruce trees were found to support a moderately diverse range of bryophytes and lichens, including two relatively rare bryophyte species. Clear patterns in vertical distribution were identified, with bryophyte richness and cover decreasing and lichen richness and cover increasing from the tree base to the upper trunk. The open spaces themselves did not appear to affect overall epiphyte diversity, with no significant differences in any of the diversity measures between edge and interior trees. The main effect of open spaces was on the epiphyte cover of the edge trees. This was related to increased light levels combined with the presence of live branches from close to ground level on the south sides of the edge trees, which produced optimum conditions for bryophytes at the tree base and lichens in the upper plots. However, this dense side-canopy negatively affected epiphyte diversity on the north sides of the edge trees. Further research is required to assess the effects of open spaces within forestry plantations on epiphyte diversity.

Glacial refugia and recolonization pathways in the brown seaweed Fucus serratus.

The last glacial maximum (20,000-18,000 years ago) dramatically affected extant distributions of virtually all northern European biota. Locations of refugia and postglacial recolonization pathways were examined in Fucus serratus (Heterokontophyta; Fucaceae) using a highly variable intergenic spacer developed from the complete mitochondrial genome of Fucus vesiculosus. Over 1,500 samples from the entire range of F. serratus were analysed using fluorescent single strand conformation polymorphism. A total of 28 mtDNA haplotypes was identified and sequenced. Three refugia were recognized based on high haplotype diversities and the presence of endemic haplotypes: southwest Ireland, the northern Brittany-Hurd Deep area of the English Channel, and the northwest Iberian Peninsula. The Irish refugium was the source for a recolonization sweep involving a single haplotype via northern Scotland and throughout Scandinavia, whereas recolonization from the Brittany-Hurd Deep refugium was more limited, probably because of unsuitable soft-bottom habitat in the Bay of Biscay and along the Belgian and Dutch coasts. The Iberian populations reflect a remnant refugium at the present-day southern boundary of the species range. A generalized skyline plot suggested exponential population expansion beginning in the mid-Pleistocene with maximal growth during the Eems interglacial 128,000-67,000 years ago, implying that the last glacial maximum mainly shaped population distributions rather than demography.

Freeze-drying for the stabilisation of shellfish toxins in mussel tissue (Mytilus edulis) reference materials

Two samples of mussels (Mytilus edulis) were collected from the southwest of Ireland. One sample contained domoic acid, the other sample contained okadaic acid, dinophysistoxin-2 and azaspiracid-1, -2 and -3. Wet and freeze-dried reference materials were prepared from each of the two samples to test for differences in homogeneity, stability and extractability of the analytes in either condition. Wet materials were homogenised, aliquoted and hermetically sealed under argon and subsequently frozen at -80 degrees C. Dry materials were similarly homogenised but frozen in flat cakes prior to freeze-drying. After grinding, sieving and further homogenisation, the resulting powder was aliquoted and hermetically sealed. Domoic acid materials were characterised using HPLC-UV, while LC-MS was used for the determination of lipophilic toxins. The extractabilities of all phycotoxins studied were comparable for wet and freeze-dried materials once a sonication step had been carried out for reconstitution of the freeze-dried materials prior to extraction. Homogeneity was assessed through replicate analysis of the phycotoxins (n = 10), and was found to be similar for wet and freeze-dried materials, for both hydrophilic and lipophilic toxins. Water contents were determined for both wet and freeze-dried materials, and particle size was determined for the freeze-dried materials. Stability was evaluated isochronously over eight months at four temperatures (-20, +4, +20 and +40 degrees C). The freeze-dried material containing domoic acid was stable over the whole duration at all temperatures, while in the wet material domoic acid degraded to some extent at all temperatures except -20 degrees C. In freeze-dried and wet materials containing lipophilic toxins, okadaic acid, dinophysistoxin-2, azaspiracid-1 and azaspiracid-2 were stable over the whole duration at all conditions, while concentrations of azaspiracid-3 changed significantly in both materials at some storage temperatures. Figure Aliquots of freeze-dried and wet mussel tissue reference materials containing the various shellfish toxins examined in the study.

Carbon sequestration determined using farm scale carbon balance and eddy covariance

Studies using eddy covariance have shown grasslands to be both sinks and sources of carbon dioxide (CO 2). However, such studies do not take into account the exports of carbon (C), such as in meat and milk and imports of C, such as off-farm derived C in cattle feed supplement. By coupling eddy covariance results with farm management data we quantified the farm scale C balance during 2004 for two dairy farms in South West Ireland. The system boundary for inputs and outputs of C is the farm perimeter. Carbon sequestration is determined as the difference between all C inputs and C outputs. Carbon inputs are similar in both farms with net ecosystem exchange (NEE) (2.9 ± 0.5 t C ha −1 year −1) accounting for 88 and 81% of C inputs in Farms A and B, respectively. Carbon in concentrate feed accounts for 12 and 19% of C inputs in Farms A and B, respectively. Respiration by cattle during the winter housing period, and respiration by cows during milking throughout the grazing season, are the largest C outputs and account for approximately half of C outputs on both farms. The other major sources of C output are milk, CH 4 produced by enteric fermentation and emitted during slurry spreading and dissolved organic carbon (DOC) in streamflow. Carbon in meat and CH 4 emissions from dung (both in the farmyard and fields) and animal slurry in farmyard storage are minor sources of C output. The annual total C inputs are 3.30 and 3.58 t C ha −1 and the total C outputs are 1.25 and 1.43 t C ha −1 in Farms A and B, respectively. The net difference is 2.05 and 2.15 t C ha −1 in Farms A and B, respectively. This suggests that both farms were net C sinks for 2004. Further work on below ground process and soil C turnover is required to determine if this C sink estimate is reflected in changes in soil C stocks. Furthermore, we estimate the global warming potential (GWP) of this grassland to be a sink for ∼1 t CO 2 equiv. ha −1 year −1.

Age constraints on the origin and growth history of a deep-water coral mound in the northeast Atlantic drilled during Integrated Ocean Drilling Program Expedition 307

Sr isotope stratigraphy provides a new age model for the first complete section drilled through a deep-water coral mound. The 155-m-long section from Challenger Mound in the Porcupine Sea-bight, southwest of Ireland, is on Miocene siliciclastics and consists entirely of sediments bearing well-preserved cold-water coral Lophelia pertusa. The 87Sr/86Sr values of 28 coral specimens from the mound show an upward-increasing trend, correspond to ages from 2.6 to 0.5 Ma, and identify a significant hiatus from ca. 1.7 to 1.0 Ma at 23.6 m below seafloor. The age of the basal mound sediments coincides with the intensification of Northern Hemisphere glaciations that set up the modern stratification of the northeast Atlantic and enabled coral growth. Mound growth persisted throughout glacial-interglacial fluctuations, reached a maximum rate (24 cm/k.y.) ca. 2.0 Ma, and ceased at 1.7 Ma. Unlike other buried mounds in Porcupine Seabight, Challenger Mound was only partly covered during its growth interruption, and growth restarted ca. 1.0 Ma.

Palynostratigraphy and palaeogeography of the Padeha, Khoshyeilagh, and Mobarak formations in the eastern Alborz Range (Kopet-Dagh region), northeastern Iran

A total of 113 surface samples collected from the Padeha, Khoshyeilagh, and Mobarak formations of Kuh-e-Ozum, northeast of Jajarm town were processed for palynomorphs, in order to determine age relationships. Well-preserved and abundant palynomorphs dominated by organic-walled-marine microphytoplankton (acritarchs and prasinophyte phycomata), miospores and subordinate chitinozoans, and scolecodonts were recovered. Seven species of prasinophyte phycomata (four genera), 19 acritarch species (14 genera), one species of chitinozoa, and 26 miospore species (19 genera) were recorded and assigned to eight local Assemblage Zones. Assemblage Zones I–IV occur in the Padeha Formation and suggest an Early Late Devonian (Frasnian) age whilst assemblages zones V–VII are present in the Khoshyeilagh Formation and indicate Late Devonian (Famennian) ages. Assemblage zone VIII, which occurs in the basal part of Mobarak Formation, suggests a Lower Mississippian (Tournaisian) age for this formation. Many of the palynomorph groups encountered are closely comparable with coeval assemblages recorded from Western Australia, southwest Ireland, England, Turkey, Saudi Arabia, North Africa, and South America, indicating the close relationship of the Iranian Platform to other parts of the northern Gondwana Domain during the time interval represented by these strata. The presence of marine palynomorphs (acritarchs/prasinophyte phycomata, chitinozoans, and scolecodonts), and shelly macrofauna (brachiopods, gastropods, and corals) in Member c of the Padeha Formation (as well as the Khoshyeilagh and Mobarak formations), together with associated miospores, indicate an open marine (moderately nearshore) depositional environment for the Upper Devonian and Lower Carboniferous deposits in northeastern Alborz Range (Kopet-Dagh region) of Iran.

The South Munster Basin of southwest Ireland

Please click here to download the map associated with this article. This paper presents a geological map at a scale of 1:75,000 of an area of about 3,500km2 of the western part of the Devonian and Carboniferous South Munster Basin of southern Ireland. The compilation utilised existing geological data from a variety of sources in association with recent mapping. Aerial photographic data were used extensively to identify structural features not previously mapped. Geological and selected topographical information were scanned to a computer and the final compilation map was digitised using Macromedia Freehand software at a scale of 1:3,125. The map was subsequently converted to a scale of about 1:75,000. The construction of the map has aided in the resolution of the stratigraphical framework for this part of the basin and has permitted a basin wide correlation of genetic depositional packages recognised in the eastern part of the basin. Some of these have been linked to a number of transgressive-regressive events during the Late Devonian and Early Carboniferous and they are correlated here into the map area. Refined information on basin architecture in association with palaeoenvironmental interpretations for the succession have been used to identify the principal sedimentation controlling structures in the basin and to assess their influence in space and time.

The South Munster Basin of southwest Ireland

The South Munster Basin of southwest Ireland

Long-term deer exclusion in yew-wood and oakwood habitats in southwest Ireland: Natural regeneration and stand dynamics

Woodland dominated by Taxus baccata is one of the rarest of European woodland types and has priority habitat status under Annex I of the EU Habitats Directive, yet little is known about its stand dynamics or the effects of long-term grazing. The abundance of naturally regenerating seedlings and saplings was monitored over a 32-year period in exclosures in a yew-wood and a neighbouring oakwood in the Killarney National Park, southwest Ireland. Both woods are heavily grazed by introduced sika deer ( Cervus nippon). Mortality, recruitment and growth of adult trees were monitored over a 20-year period. Comparison was made with unfenced plots adjacent to each of the exclosures. Regeneration in the yew-wood exclosures was chiefly by Ilex aquifolium, Sorbus aucuparia and Fraxinus excelsior. No Taxus baccata saplings were recorded and seedlings of this species were very rare throughout the duration of the experiment. Taxus baccata trees which died during the 20-year monitoring period were significantly smaller than those which survived, indicating that self-thinning is occurring and the wood in its present form may be of relatively recent origins. Changes in adult tree species composition suggest that yew woodland in Ireland may develop from a yew-hazel scrub woodland sere. A variety of species regenerated in the oakwood exclosures, including Taxus baccata, and dense holly thickets formed in several areas. Quercus petraea failed to regenerate beneath the oak canopy. We conclude that chronic heavy grazing in the Killarney woodlands strongly influences the natural regeneration of several tree species. Research into the scientific manipulation of grazing levels in temperate woodlands is required. However, grazing intensity is not the only factor affecting regeneration, canopy conditions in particular are also likely to be of high significance, and this should be reflected in management plans.

Modeling of net ecosystem exchange and its components for a humid grassland ecosystem

We measured the net ecosystem exchange (NEE) of a managed humid grassland in southwest Ireland from 2002 to 2004 with an eddy covariance (EC) system. In addition, a process‐based biogeochemical model (PaSim) incorporating land management practices such as grazing and grass harvesting was used to simulate the carbon dynamics. The modeled NEE of 2.6, 2.7 and 3.4 t C ha−1 (uptake) for 2002, 2003 and 2004 compares well with the measured NEE of 1.9, 2.6 and 2.9 t C ha−1. There is good agreement between the model output and the EC observations in the growing season but not so good in the winter period. The year‐on‐year increase in measured NEE is partly attributed to a circa 4% year‐on‐year increase in annual photosynthetic photon flux density (QPPFD). The year of lowest NEE (2002) was associated with highest rainfall (1785 mm) and lowest QPPFD. In the wettest year, grass harvesting was delayed by a month, resulting in a reduced NEE. The management of grassland in regions of high rainfall is dependent on weather conditions. If wet conditions become more prevalent (e.g., as a result of climate change), grasslands in such regions may shift from intensive to extensive management with further reductions in NEE. The reasonable agreement between the model predictions and the EC measurements demonstrates the potential of the model for applications such as upscaling EC measurements to regional scales and predicting responses of grasslands to climate change.

Behavioural interactions of seabirds with suspended mussel longlines

Increased abundances of a number of seabird species have been found in areas of mussel longline aquaculture (compared to control sites) in a recent study at Bantry Bay, southwest Ireland. The aim of this study was to investigate whether this form of mussel aquaculture also affects the activity budgets and foraging behaviour of these seabirds. Scan-sampling was used to compare seabird activity budgets between three areas of mussel longline aquaculture and three control sites. Foraging activities of Great-Northern Divers Gavia immer, an Annex 1 species under the Euopean Union's Birds Directive, were also compared between sites using focal sampling. The behaviour of gulls (Larus sp.), Cormorants Phalacrocorax carbo, Shags Phalacrocorax aristotelis and Great-Northern Divers (but not auks, Alcidae) differed significantly between areas of mussel aquaculture and control sites in this study. Mussel suspension buoys were heavily utilized by gulls, cormorants and shags as safe perching platforms for preening activities. Gulls also fed extensively on epifauna attached to the buoys. Great-Northern Divers spent more time snorkelling (head submerged in search of food) in mussel sites than in the control sites, however dive duration and visible foraging success rates did not differ significantly between sites. Overall, the environmental impact of mussel suspension culture appears to be positive or neutral on marine bird species occurring at this study site.

Crustal velocity structure of the British Isles; a comparison of receiver functions and wide-angle seismic data

Magmatic underplating at the base of the continental crust is thought to be an important consequence of mantle plume activity. Geochemical evidence supports the hypothesis of underplating beneath the British Tertiary Igneous Province during Palaeocene times, a process that has been invoked to explain at least part of the observed pattern of Cenozoic denudation and consequent offshore deposition. This study uses receiver functions to independently test the results of modelling of four wide-angle seismic lines across the British Isles, several of which indicate the presence of a lens of high-velocity material at the base of the crust. This lens has been interpreted as evidence of Palaeogene magmatic underplating. Receiver functions were calculated for three permanent and two temporary three-component broad-band seismometers. In order to detect P-to-S conversions from intracrustal velocity discontinuities, high frequencies were preserved in the calculation of the receiver functions. Receiver functions were modelled using the delay times of the P-to-S converted arrivals only, with constraints on the VP and VP/VS structure imposed from controlled source data. This pragmatic method of interpreting receiver function data agrees well with the results of applying an established inversion technique. Resulting crustal velocity models are broadly consistent with the velocity models from the wide-angle lines, showing evidence for a four-layer crust with laterally varying Moho depths of between 33 ± 2.5 km beneath southwest Ireland, 32 ± 2.5 km beneath northern and eastern Ireland, 31 ± 2 km beneath the Isle of Man and 35 ± 3 km beneath northern England. While these velocity models are consistent with the presence of a lower crustal layer, receiver functions are insensitive to the P-wave velocity structure, and so unfortunately they cannot be used to independently constrain the P-wave velocity of the lower crust, which is an important diagnostic of the presence of magmatic underplating.

Breeding densities of Robin Erithacus rubecula in different habitats: the importance of hedgerow structure

Capsule Territory density varied between habitat types and displayed a clear relationship with certain macro- and micro-habitat characteristics. Aims To investigate the role of habitat and structural hedgerow components on breeding densities of Robins and to provide baseline territory density estimates for the Robin in a range of habitats in southwest Ireland. Methods Robin territory densities were estimated at 39 sites of five major habitat types in southwest Ireland. A modified CBC-type technique was used to census Robins and additional habitat data were collected at each site. One-way ANOVA with post hoc testing was used to investigate the population densities between the different habitat groupings, and a principal component analysis of habitat data was used to generate independent variables for a stepwise regression where territory density per hectare and territory density per kilometre were, in turn, the dependent variables. Results Population densities varied significantly between habitat types. The highest Robin territory densities were encountered in semi-improved grassland sites and the lowest values in suburban gardens. The mean territory density per hectare in all farmland habitats surveyed was notably higher than published estimates for British farmland and woodland. The quantity of hedgerow available appeared to be an important factor in determining Robin abundance on farmland. There was also a relationship between various hedgerow structural components and Robin territory density. Conclusion Our analysis indicated that high bushy hedgerows with narrow banks and low basal vegetation positively influenced the number of Robin territories per hectare. We also conclude that if basal vegetation becomes overgrown at some critical point it impedes detection of prey by Robins, even when there are many available foraging perches.

Breeding biology of the Song Thrush Turdus philomelos in an island population

Capsule Breeding characteristics were explained by agricultural intensification, climate, latitude and insular syndrome. Aims To describe the timing of breeding, clutch size and number of nestlings hatched and fledged, assess nesting success and investigate growth development of nestlings in Song Thrush. Methods Nests were monitored intensively in County Cork, southwest Ireland, and extensively countrywide by volunteers. The number of nesting attempts, location, surrounding habitat, nest height above ground and sea level, date of first egg, nesting stage, clutch size, number of chicks hatched and fledged and causes of nest failure, daily nest survival, fledglings per attempt (FPA), reproductive output per attempt (ROA) and seasonal productivity were recorded. Results Data collected from 100 nests during 2001–03 were available for analysis. The breeding season extended from mid-March to late June. Only 3% of nests represented third broods. Mean clutch size was 4.1 (±0.62), number of hatchlings was 3.7 (±0.92) and number of fledglings was 3.7 (±0.89). Clutch size and brood size, at hatching and fledging, significantly differed with month, year, nesting attempt, latitude and altitude. FPA was calculated as 0.75 and ROA as 1.13. Seasonal productivity was calculated as 2.7 young fledged from 3.7 nesting attempts. Daily nest survival rates were: egg stage 0.9362 (±0.0126), incubation stage 0.9505 (±0.0121) and nestling stage 0.9609 (±0.0096). First broods had higher, though not significantly, daily failure rates than second broods during all nest stages. Weather did not have any significant effects on nest survival or outcome. Most nest failures were due to predation at both egg and chick stages. Avian predation was more common than mammalian. Conclusion Differences in breeding biology characteristics between Ireland and other European countries may be explained by agricultural intensification, climate, latitude and insular syndrome. The data presented provide a baseline for future monitoring and may also help in conservation measures in areas of decline.

A 15-month study of zooplankton ingestion by farmed mussels ( Mytilus edulis) in Bantry Bay, Southwest Ireland

There is a growing body of evidence to suggest that bivalve molluscs routinely ingest zooplankton. To elucidate further these observations, a 15-month study of zooplankton ingestion by farmed mussels was conducted using mussel long-lines in Bantry Bay, Ireland. Stomach content analysis of the mussels showed that there was evidence of zooplankton ingestion throughout the sampling period, but that highest mean numbers of zooplankters were ingested by mussels in the spring and summer months. Various zooplankton species were present in mussel stomachs. Harpacticoid copepods were found more often in stomach contents than calanoid copepods, probably due to their proximity to the bivalves' inhalent siphons. Barnacle cyprids featured in large numbers in stomach contents, but only for a period of 3 months which broadly corresponded with their pelagic phase. Sizes of ingested zooplankton ranged from 126 μm to 6 mm, but more of the smaller zooplankters (e.g. crustacean nauplii) were ingested. When lengths of ingested copepods were compared with those found in plankton net samples, it was found that the net-sampled copepods were significantly larger than those found in mussel stomachs, suggesting that mussels select for smaller categories within the zooplankton available to them. Soft bodied zooplankton was rarely found in mussel stomachs but their absence may be due to rapid digestion or they may have been destroyed in the preservation process. Ingestion of zooplankton by bivalves is discussed in the context of the impacts mussel farms have on resident zooplankton populations.

Heterochrony in Haplomesus (Crustacea: Isopoda: Ischnomesidae): revision of two species and description of two new species

Two new species of Ischnomesidae, Haplomesus celticensis sp. nov. and Haplomesus hanseni sp. nov. are described from the southwest of Ireland and the Argentine Basin respectively. Both species lack the expression of pereopod VII, a characteristic that we argue is produced by progenesis, not neoteny as suggested by Brökeland & Brandt (2004). Haplomesus angustus Hansen, 1916 and Haplomesus tropicalis Menzies, 1962, also lack pereopod VII and are revised from the type material. The original description of Haplomesus angustus Hansen, 1916 describes the adult type specimen as a juvenile; the original description of Haplomesus tropicalis Menzies, 1962 fails to mention the lack of pereopod VII. Progenesis is discussed for the above species and within the family Ischnomesidae as a whole.

Shear‐wave splitting observations across southwest Ireland

Shear‐wave splitting analyses have been carried out on teleseismic data from the southwest of Ireland acquired during the Irish Seismological Lithospheric Experiment (ISLE). The data were gathered over a ten‐month period by a temporary network of 23 broadband and short‐period stations. The results are compared with data from two permanent broadband seismic stations, which have recorded SKS and SKKS phases for up to 10 years. The purpose of the experiment was to investigate possible anisotropy within the crust and mantle related to Caledonian deformation. Here we report splitting results which show an average delay time of 1.2 s and a variation of fast‐polarisation direction with back azimuth that surprisingly suggests a much deeper origin for anisotropy than was anticipated.

Late quaternary paraglacial sedimentation in the Macgillycuddy's reeks, southwest Ireland

Abstract Talus slopes in the Curraghmore cirque basin in the Macgillycuddy's Reeks have developed since the end of the Glenavy Stadial (Last Glacial Maximum; MIS 2). The site lay outside Younger Dryas glacier limits and, as a result, thick rockfall and debris flow accumulations form a significant landform assemblage draping lower hillslopes. Rockwall retreat rates since icesheet deglaciation average 0.08mm per year, and 0.2mm per year up to the beginning of the Holocene.