SW Ireland Research Articles

New species and records of Heterospio (Annelida, Longosomatidae) from continental shelf, slope and abyssal depths of the Atlantic Ocean, Pacific Ocean, Indian Ocean and adjacent seas.

Nineteen species of the rare polychaete genus Heterospio are reported, 15 of which are new to science. The status of H. longissima Ehlers, 1874, the type-species, is reviewed. The specimens examined are from several locations in the North Atlantic Ocean, Gulf of Mexico, Caribbean Sea, off Br azil, the Indian Ocean, the Pacific Ocean off California, New Zealand, Australia, and the South China Sea. Deep-water samples from the western North Atlantic Ocean collected by the late Drs. H.L. Sanders and R.R. Hessler that were reported by Hartman as H. longissima were re-examined and referred to two new species, H. hartmanae n. sp. (abyssal depths, New England to Bermuda transect) and H. guiana n. sp. (bathyal depths off Suriname). Other materials from the Sanders/Hessler North Atlantic collections were also examined and referred to two additional species, H. canariensis n. sp. (deep water off Canary Islands) and H. southwardorum n. sp. (Bay of Biscay) as well as H. cf. reducta from off SW Ireland in bathyal depths. New collections from the North Atlantic region include additional materials of H. hartmanae n. sp. (deep water off the Mid-Atlantic and SE USA), H. aruba n. sp. (Caribbean Sea), H. bathyala n. sp. (deep water off SE USA), and H. dibranchiata n. sp. (deep water, Gulf of Mexico). Heterospio paulolanai n. sp. is from shelf depths off southeastern Brazil. Heterospio knoxi n. sp. is from the North Island of New Zealand, H. ehlersi n. sp. is from the Gulf of Thailand, in the South China Sea, H. bidentata n. sp. is described from deep water in the Coral Sea off eastern Australia, and H. alata n. sp. and H. brunei n. sp. are described from deep water off the Island of Borneo in the South China Sea. Heterospio africana n. sp. and H. antonbruunae n. sp. are described from off east Africa in the Mozambique Channel. New records and descriptions of H. catalinensis, H. indica, and H. peruana are presented. The 15 new species reported here nearly triple the number of previously known species of Heterospio, with 23 species now recognized. All known species are tabulated and compared.

Petrogenesis of the Limerick Igneous Suite: insights into the causes of post-eruptive alteration and the magmatic sources underlying the Iapetus Suture in SW Ireland

The Limerick Igneous Suite (LIS) in County Limerick, SW Ireland, contains two distinct basaltic igneous units: the Knockroe and Knockseefin, which are expressed as hypabyssal intrusions, porphyritic dykes, diatremes, lava flows, agglomerates and tuffs. These units make up two distinct evolutionary trends: the Knockroe igneous units which range from alkaline basalts to trachyandesites, and the Knockseefin igneous units which range from alkaline basalts to basanites. U‒Pb dating of apatite establishes a primary crystallization age of c. 350 Ma for the Knockroe units. Strontium and Nd isotopes from the least-altered Knockroe bulk rock samples range over 0.70301–0.70454 and 0.512457–0.512493, respectively. The Sr isotopes for the least-altered Knockseefin samples are similar, ranging over 0.70325–0.70386, but the Nd values are slightly more radiogenic, spanning 0.512431–0.512437. Altered samples are buffered against changes in Nd, but some show excursions towards radiogenic Sr, suggesting contamination from Carboniferous seawater and/or introduction of Rb. Rb–Sr calculations conducted on altered Knockroe samples returned ages within uncertainty of the U‒Pb dates. The bulk rock isotope values, normalized trace element plots as well as Zr/Sm, Ce/Pb and Nb/U values demonstrate the LIS is comparable to ocean island basalts and Ce/Y and Zr/Nb values suggest the units likely originated from low degrees of partial melting likely caused by extension related to the amalgamation of Laurussia and Gondwana. Supplementary material: ESM 1, whole rock geochemistry data; ESM 2, apatite chemistry and geochronology data; and ESM 3, supplementary figures are available at https://doi.org/10.6084/m9.figshare.c.6297395

Character of advance and retreat of the southwest sector of the British-Irish Ice Sheet during the last glaciation

Relict landforms and sediments across former glaciated settings provide information about ice-sheet dynamics and can contribute to the understanding of the behaviour of contemporary ice masses, for which observations are limited in spatial and temporal extent. In this study, we focus on the shelf offshore southwest Ireland, in the Celtic Sea, which was once occupied by the Irish Sea Ice Stream (ISIS), the largest ice stream draining the southern portion of the marine-terminating British-Irish Ice Sheet (BIIS). Newly acquired high-resolution multibeam echosounder, sub-bottom and core data enabled the investigation of the shelf geomorphology and of the sedimentology and chronology of glacial and glacimarine sediments. A suite of drumlins records ice sheet flow from the coastline towards the central part of the shelf in southwest Ireland. Pre-existing highs in the seafloor topography promoted the formation of arcuate and transverse landforms interpreted as a grounding-zone wedge and moraines and they document episodic retreat of the ISIS across this portion of the shelf. Observed lithofacies show consolidated subglacial till and laminated fine muds. The sediments provide evidence of ice grounded ca. 30 km off the south-west Irish coastline with subsequent deglaciation occurring under glacimarine conditions. These new data refine the current reconstructions of the dynamics of the southern BIIS. They reveal for the first time the interplay of marine- and land-based ice and the presence of grounded ice offshore SW Ireland. This study highlights the importance of high-resolution data in revealing palaeo-landscapes as valuable analogues to test possible scenarios of modern ice sheet changes.

Crystal-Liquid Segregation in Silicocarbonatite Magma Leads to the Formation of Calcite Carbonatite

Abstract A suite of silicocarbonatite and lamprophyre rocks from SW Ireland, with mantle affinity and primitive composition, are used as a proxy for parental carbonated silicate magmas to model early magmatic evolution. Reconstruction of volatile ratios is validated using global occurrences. At 1200°C, the point at which melts transition from ionic liquids with exceptionally low viscosity (0.06 PaS) to covalently polymerised liquid (viscosity up to 1.3 PaS) is 33 mol% SiO2. Incremental and significant increase in magma density accompanies magma ponding, due to dehydration of magmas from model molar CO2/(CO2 + H2O) of 0.60 in plutonic settings to 0.75 for initial subvolcanic magmas. Magma-crystal density differences dictate that repeated influxes of magmas into an inflating magma chamber sustain a mechanical boundary layer between dense (silicate and oxide) mineral layers and a calcite ± phlogopite flotation assemblage. The range of critical CO2 concentration at which calcite floats (10–13 wt% CO2) may be extended by the presence of additional volatiles and fluid bubbles. The model accommodates a range of phenomena observed or inferred for alkaline/carbonatite complexes, including the following: 1, a growing calcite-dominated flotation assemblage with an apparently early magmatic mineralisation; 2, a residual liquid with high concentrations of incompatible metals; 3, variable carbonatite–pyroxenite–phoscorite rock relations; and 4, multiple phases of overprinting metasomatism.

The Irish Atlantic CoCliME case study configuration, validation and application of a downscaled ROMS ocean climate model off SW Ireland

This ocean numerical modelling study is focused on the shelf waters off southwest Ireland. Outputs from the model are used to provide scientists and policy makers with climate change information related to oceanic conditions that influence harmful algal blooms in the region. Four simulations were developed to include a 20-year hindcast simulation (1997–2016), a 31-year historical simulation (1975–2005), and two 30-year future climate model projections (2006–2035) for the representative carbon pathways (RCP) 4.5 and 8.5 scenarios. We evaluated the hindcast model skill by comparing the simulation outputs with measured observational data and calculated statistics such as the bias, and the root mean square error (RMSE). The observations consisted of satellite sea surface temperature and, CTD temperature and salinity profile data collected in Irish waters. The sea surface temperature RMSEs between the 20-year hindcast simulation and the satellite data were ca. 0.50°C. A minimum RMSE of ca. 0.20°C was recorded in December 2015. The basin-averaged bias (difference) and RMSE for near bottom temperature between the RCP 4.5 and the historical simulation was 0.14°C and 0.27°C respectively. The sea surface temperature anomaly pattern for the RCP 8.5 shows warming across the whole model domain. The sea surface salinity and near bottom salinity climate simulation anomaly maps indicate a general freshening on the southwest Irish shelf. A change of ca. 0.2 sea surface salinity and near bottom salinity was observed. The RCP 8.5 simulation shows the highest current velocities when compared to other simulations. The Irish coastal current pattern under the RCP 8.5 scenario appears very intense and well defined with a velocity > 20 [cm/s].

Response of intertidal barnacles to air temperature: Long-term monitoring and in-situ measurements

A twenty-five year (1994–2018) survey at 10 rocky sites within Lough Hyne Marine Reserve (SW Ireland) showed that, despite considerable spatial and temporal patchiness, three barnacle species (Chthamalus stellatus, Semibalanus balanoides, and Austrominius modestus) declined in overall abundance in the early 2000s, particularly at three sites. There was no clear response of A. modestus or C. stellatus to the cold winters of 2010 and 2011. In 2004, however, S. balanoides declined suddenly, but showed a slight recovery after the cold winter of 2010 to maintain sparse populations in the lough, but remained abundant outside the lough. A fourth species, Chthamalus montagui, showed a different pattern, with wide fluctuations in abundance but no overall decline. Changes in the Atlantic Multidecadal Oscillation may have influenced the overall composition of barnacle populations. Rising maximum air temperatures, resulting in high body temperatures recorded for A. modestus even during mild days, are suggested to have impacted the barnacle populations as a result of the prolonged aerial exposure times caused by the lough's asymmetric tidal pattern.

Nitrogen fertilizer replacement value of dairy soiled water in grass swards as affected by timing and rate of application

AbstractDairy soiled water (DSW) is a dilute mixture of cow faeces, urine, milk and detergents produced from the washing of milking plant and holding areas, and contains nutrients. Its N fertilizer replacement value (NFRV), compared to inorganic fertilizer (IF), was determined in a plot experiment on two grassland soils (well‐drained and poorly drained) in SW Ireland over a year with 4 N rates (0, 15, 22 and 30 kg N/ha), nine application timings and four replicates. Herbage was harvested at 4 and 8 weeks after each application to determine the total 8‐week DM yield. While caution is required, as results are based on only two sites and one year, DSW increased herbage production and showed potential to substitute for inorganic fertilizer N with surprisingly high NFRVs of 72 to 90%, potentially offering cost savings to farmers, improved N use efficiencies and reduced risk of nutrient loss to the environment. High NFRV may be due to factors such as the even spread and infiltration of DSW, low rates of ammonia emission or a stimulatory effect on the release of soil N. Yield increased significantly (p < .001) with N rate from approximately 1,200 kg DM ha−1 at 0 kg N/ha to approximately 1,700 kg DM ha−1 at 20–30 kg N/ha but application beyond approximately 20 kg N/ha was associated with increasingly diminished yield response. Yield response was greatest from March to July and poor response in winter suggests a greater risk of N loss during this period.

New Estimates of 24-Hour Probable Maximum Precipitation (PMP) for the British Isles

Estimates of PMP are needed in order to estimate the spillway design flood for dams which must be capable of safely passing the probable maximum flood (PMF). For over forty years the standard estimates of the Flood Studies Report (FSR) have almost always been used. However, since then several studies have shown that these values are too low, and new estimates for South West England and then Britain were published. This paper extends these studies to include the whole of the British Isles. The study uses 6570 station years’ data in a new method of frequency analysis that identifies part of the data which represents the long term situation. Further analyses to support the results of this approach have been produced from the in situ maximisation of 12 historic storms using World Meteorological Organisation methods. The results are broadly consistent with those obtained from frequency analysis. Values of 24 hour PMP in Britain range from 600 mm in upland areas of the Lake District, to 400 mm in parts of East Anglia. This range of values is present in Wales and parts of South West England. For Ireland the highest values are over the upland areas, such as in the Wicklow Mountains (550 mm) and SW Ireland (600 mm), while in the lowlands values around 350 mm can be expected. The question of uncertainty in estimating PMP is considered, most of which is due to the temporal and spatial shortcomings of the data. The implications for the probable maximum flood (PMF) and spillway design flood mean that widespread reassessment of dam safety should be carried out at once.

A review of the ecology and status of the Kerry Lily Simethis mattiazzii (S. planifolia) Asphodelaceae in Ireland

The distribution, habitat and genetic diversity of Irish populations of the Kerry Lily (Simethis mattiazzii) are described. All sites known in 2009, centred around Kenmare Bay in SW Ireland, were sampled. The species occurs in a relatively uniform plant community, classified as 4030 Dry Heath within a low-lying coastal heath complex. A preliminary genetic investigation involving analysis of 21 chloroplast and nuclear gene regions revealed no genetic diversity in the samples examined, suggesting that the species in Ireland comprises a number of meta-populations, within one large, single population confined to the Derrynane area on the Iveragh peninsula in South-west Kerry (v.c.H1) and one on the north of the Beara peninsula, across Kenmare Bay from Derrynane, in West Cork (v.c.H3). A sixth site, at Cahergarriff on the south of the Beara Peninsula has since been discovered. Of the 5,750 flowering plants recorded in 2009, the biggest meta-population, which also had the highest plant density, numbered 2,364, on Abbey Island, near Derrynane. Results from two brief surveys in 2020 indicate that the populations have reduced in extent and size since 2009. The genetic results so far suggest that the species is genetically depauperate in Ireland, such that the Irish populations may in fact be only represented by a single, or narrow, founder genotype and may be the result of a one-off introduction. The potential mode of arrival of the species to Ireland is discussed in relation to trade with continental Europe, where its distribution is greatest in SW France and western Iberia. A follow-up genetic study is required to confirm these results and explore a putative point of origin for the species in Ireland. Conservation issues are addressed in the light of these observations.

Stressed from above and stressed from below: dissolved oxygen fluctuations in Lough Hyne, a semi-enclosed marine lake

AbstractDissolved oxygen (DO) concentrations of the fully marine Lough Hyne, SW Ireland, were sampled in biologically different habitats between 2014 and 2019 to investigate the declining water quality in the marine reserve and the severity of oxidative stress on benthic communities. DO was measured above and below shallow subtidal rocks, in the Rapids connection to the Celtic Sea, in seagrass meadows (Zostera marina), and at various water depths (1–15 m) in the South Basin. DO values above rocks were normoxic to hyperoxic in daytime (7.8–17.3 mg l−1); below rocks were often hypoxic (0.24–2 mg l−1). South Basin sites experienced hypoxia less often than the North Basin, except for the Goleen, presumably due to differential current flow. DO fluctuations occurred in spring (before ephemeral macroalgae proliferate), summer (when algal mats smother the benthos), and autumn (when macroalgae decay). While the Rapids were normoxic, the seagrass meadows below them exhibited periodic DO stress. Labhra Cliff (9–14.5 m) was normoxic to hyperoxic in autumn but experienced suboxic and hypoxic events in summer. Many organisms in Lough Hyne are experiencing periods of hypoxia below their published sublethal limits, the effects of which could be exacerbated by periodic hyperoxia.

The vein-hosted copper deposits of the Allihies mining area, SW Ireland; a new structural and chronological evaluation

This paper presents new data for historical vein-hosted copper sulfide deposits in the Late Paleozoic Munster and South Munster basins of SW Ireland. Detailed mapping, 3D modelling, fluid inclusion microthermometry and geochronology from the Allihies area of the Beara Peninsula have led to a new interpretation of the timing and development of ore mineralization. Macro- and microstructural studies reveal that the ore-bearing, mainly east–west-striking quartz veins are directly related to early extensional, basinal normal faults. Molybdenite Re–Os dating of the main-stage Cu lode yields ages from 367.3 ± 5.5 to 366.4 ± 1.9 Ma. This early vein system experienced subsequent late Carboniferous Variscan deformation, including cleavage development, sinistral SW–NE strike-slip faulting, cataclastic deformation and recrystallization. The new timing of Cu mineralization in SW Ireland has major implications for its relationship to the base metal deposits of the Irish Midlands. Supplementary material: A video file showing a 3D model of the major lodes and the underground workings at Mountain Mine, and Excel spreadsheets showing fluid inclusion measurements and sample locations of the Allihies Copper Mining District are available at https://doi.org/10.6084/m9.figshare.c.4875015

Drivers of Land Abandonment in the Irish Uplands: A Case Study

Abstract Land abandonment is a complex multi-dimensional process with interlinked economic, environmental and social aspects. This paper presents a case study of an isolated hill sheep farming community in SW Ireland, where a combination of low incomes, ageing population, lack of successors and strong environmental constraints are perceived to be among the main factors leading to their demise. However, the uplands they have grazed for generations are of high nature conservation value, and depend on active management to maintain both their ecology and landscapes. The research, which is based on a combination of interviews and farming systems research, highlights the misfit between what the mountain can produce, light hill lamb, and what the globalised market demands. The paper argues that if ‘farming for conservation’ is the new function of such farming systems, then we should consider decoupling public goods payments from agricultural subsidies, along with integrating agriculture in disadvantaged areas within a broader rural development framework. The research aims to fill the gap between macro policy and the micro reality of an upland community on a self-declared ‘tipping point’.

Erratum for ‘The provenance of the Devonian Old Red Sandstone of the Dingle Peninsula, SW Ireland; the earliest record of Laurentian and peri-Gondwanan sediment mixing in Ireland,’ Journal of the Geological Society, London, 175, 411–424

Samples in this paper have been assigned formations based on the Geological Survey of Ireland shapefile released prior to the commencement of the study. However, the authors were not aware that, since obtaining the samples, an updated shapefile had been released. This update affects three of the four apatite samples assigned to the Lower Devonian Ballymore Formation. The location of samples Mb-1, Mb-4 and Mb-5 now places them well within the undifferentiated, Upper Devonian Slieve Mish Group. As outlined in our paper, the apatite ages were originally produced concurrently with apatite fission track analysis and were later used in our study to provide additional provenance information in support of the detrital zircon geochronological data. In the second paragraph of the discussion section we say the following: et al. (1999) obtained an age of 411 Ma for the Cooscrawn Tuff Bed in the Ballymore Formation, which is older than 22 of the 70 detrital apatites analysed in this formation. The reassignment of the three samples to the Upper Devonian Slieve Mish Group nullifies the above statement. However, our interpretation that the depositional age of the Ballymore Formation is younger than the 411 Ma age given by Williams et al. (1999) is predominantly based upon the evidence given by the six youngest detrital zircons from the formation which underlies the Ballymore Formation (i.e. the Slea Head Formation). These zircons give a concordia age of 405 ± 4 Ma. This suggests that the Ballymore Formation was more than likely deposited after 409 Ma. We do not believe that the reassignment of the three samples has any major impact on our provenance interpretations. The ∼420 Ma age of the majority of the apatites in samples Mb-1, Mb-4 and Mb-5 actually fits with the range of Palaeozoic detrital zircons in sample AK-17 which was taken from the Slieve Mish Group, thereby supporting minor input of rocks affected by end-Scandian metamorphism.

Benthic foraminifera in a deep-sea high-energy environment: the Moira Mounds (Porcupine Seabight, SW of Ireland)

Cold-water coral ecosystems represent unique and exceptionally diverse environments in the deep-sea. They are well developed along the Irish margin, varying broadly in shape and size. The Moira Mounds, numerous small-sized mounds, are nestled in the Belgica Mound Province (Porcupine Seabight, North-East Atlantic). The investigation of living (Rose Bengal stained) and dead benthic foraminiferal assemblages from these mounds allowed to describe their distribution patterns and to evaluate their response to environmental variability. Quantitative data was statistically treated to define groups of species/genera associated to specific habitats. The Moira Mounds differ from their larger neighbours by the reduced spatial variability of benthic foraminiferal assemblages, living assemblages only distinguishing coral-rich and coral-barren areas. The ecological needs of corals are highlighted by the abundance of Alabaminella weddellensis and Nonionella iridea, phytodetritus-feeding species in coral supporting sediments. Living foraminifera in sediments from the Moira Mounds concentrate in the upper first centimetre. Infaunal species may be affected by bioturbation and/or reworking by the strong currents in the area. Dead foraminiferal assemblages from the Moira Mounds resemble those described for the sandwave facies in adjacent giant mounds, suggesting similar processes in facies deposition.

Across‐axis variations in petrophysical properties of the North Porcupine Basin, offshore Ireland: New insights from long‐streamer traveltime tomography

AbstractThe Porcupine Basin is a Mesozoic failed rift located in the North Atlantic margin, SW of Ireland, in which a postrift phase of extensional faulting and reactivation of synrift faults occurred during the Mid–Late Eocene. Fault zones are known to act as either conduits or barriers for fluid flow and to contribute to overpressure. Yet, little is known about the distribution of fluids and their relation to the tectono‐stratigraphic architecture of the Porcupine Basin. One way to tackle this aspect is by assessing seismic (Vp) and petrophysical (e.g., porosity) properties of the basin stratigraphy. Here, we use for the first time in the Porcupine Basin 10‐km‐long‐streamer data to perform traveltime tomography of first arrivals and retrieve the 2D Vp structure of the postrift sequence along a ~130‐km‐long EW profile across the northern Porcupine Basin. A new Vp–density relationship is derived from the exploration wells tied to the seismic line to estimate density and bulk porosity of the Cenozoic postrift sequence from the tomographic result. The Vp model covers the shallowest 4 km of the basin and reveals a steeper vertical velocity gradient in the centre of the basin than in the flanks. This variation together with a relatively thick Neogene and Quaternary sediment accumulation in the centre of the basin suggests higher overburden pressure and compaction compared to the margins, implying fluid flow towards the edges of the basin driven by differential compaction. The Vp model also reveals two prominent subvertical low‐velocity bodies on the western margin of the basin. The tomographic model in combination with the time‐migrated seismic section shows that whereas the first anomaly spatially coincides with the western basin‐bounding fault, the second body occurs within the hangingwall of the fault, where no major faulting is observed. Porosity estimates suggest that this latter anomaly indicates pore overpressure of sandier Early–Mid Eocene units. Lithological well control together with fault displacement analysis suggests that the western basin‐bounding fault can act as a hydraulic barrier for fluids migrating from the centre of the basin towards its flanks, favouring fluid compartmentalization and overpressure of sandier units of its hangingwall.

Long-term fluctuations in epibiotic bryozoan and hydroid abundances in an Irish sea lough

Recent declines in coastal water quality in SW Ireland have led to changes in the abundance of algal-associated bryozoans and a hydroid. These common North Atlantic species offer considerable potential as indicator species for reduced oxygen conditions due to habitat degradation. Annual monitoring for more than two decades (1994–2016) at 10 rocky shore sites within Lough Hyne Marine Reserve, SW Ireland revealed a significant reduction in abundance of the ctenostome bryozoan, Flustrellidra hispida, through time, coincident with the development of daily, extreme, shallow water oxygen fluctuations (hyperoxia and hypoxia) due to eutrophication. In contrast, the ctenostome, Alcyonidium species-complex, increased significantly during the two-decade period. The thecate hydroid, Dynamena pumila, did not show any significant decadal-scale pattern but temporal variability in abundance increased since 2010. Abundances of F. hispida and D. pumila were positively correlated with estimates of water flow. F. hispida inhabited a variety of algal hosts but appeared most sensitive (of the taxa surveyed) to variation in habitat quality, especially experimentally reduced levels of dissolved oxygen (<4 mg L−1). Such sensitivity indicates F. hispida could be useful as an indicator of environmental change, whereas D. pumila was more robust in response to reduced oxygen with 38.6% of the hydroid zooids being able to survive under hypoxic conditions as compared to only 0.2% of the bryozoan zooids. Given the widespread European distribution of these species, they offer the opportunity to act as important bioindicators of water quality and hence environmental degradation in north temperate intertidal systems.

The provenance of the Devonian Old Red Sandstone of the Dingle Peninsula, SW Ireland; the earliest record of Laurentian and peri-Gondwanan sediment mixing in Ireland

The Lower Old Red Sandstone in southern Ireland is hosted in the Early Devonian Dingle Basin, which lies immediately south of the Iapetus Suture on the Dingle Peninsula, County Kerry. The basin developed as a post-Caledonian pull-apart structure prior to Acadian deformation, which in turn was followed by end-Carboniferous Variscan deformation. Detrital zircon U–Th–Pb geochronology is complemented by mica Ar–Ar and apatite U–Pb geochronology to gain a comprehensive understanding of the provenance of the Lower Devonian Lower Old Red Sandstone of the Dingle Basin and assess contributions of major tectonic components (e.g. Laurentia, Ganderia). Sedimentary rocks in the Lower Old Red Sandstone have similar detrital zircon age distributions, which are dominated by c. 1.2 Ga zircons as well as late Neoproterozoic grains. This indicates a dominant contribution of detritus of Laurentian affinity as well as contributions from westerly and southerly derived Ganderian detritus. Caledonian uplift of the area north of the Iapetus Suture would have facilitated a large contribution of (peri-)Laurentian material. The Upper Old Red Sandstone on the Dingle Peninsula has a distinctly different detrital zircon character including few late Neoproterozoic zircons and abundant zircons of c. 1.05 Ga age, indicating sediment derivation only from Laurentia and no recycling from the Lower Old Red Sandstone. Supplementary material: The full detrital U–Pb zircon and apatite analytical dataset and the revised detrital mica age dataset are available at https://doi.org/10.6084/m9.figshare.c.3971862

Influence of artificial drainage system design on the nitrogen attenuation potential of gley soils: Evidence from hydrochemical and isotope studies under field-scale conditions

In North Atlantic Europe intensive dairy farms have a low nitrogen (N) use efficiency, with high N surpluses often negatively affecting water quality. Low feed input systems on heavy textured soils often need artificial drainage to utilise low cost grassland and remain profitable. Heavy textured soils have high but variable N attenuation potential, due to soil heterogeneity. Furthermore, drainage system design can influence the potential for N attenuation and subsequent N loadings in waters receiving drainage from such soils. The present study utilises end of pipe, open ditch and shallow groundwater sampling points across five sites in SW Ireland to compare and rank sites based on N surplus, water quality and “net denitrification”, and to develop a conceptual framework for the improved management of heavy textured dairy sites to inform water quality N sustainability. This includes both drainage design and “net denitrification” criterion, as developed within this study.N surplus ranged from 211 to 292 kg N/ha (mean of 252 kg N/sourha) with a common source of organic N across all locations. The predicted soil organic matter (SOM) N release potential from top-subsoil layers was high, ranging from 115 to >146 kg N/ha. Stable isotopes analyses showed spatial variation in the extent of specific N-biotransformation processes, according to drainage location and design. Across all sites, nitrate (NO3-N) was converted to ammonium (NH4+-N), which migrated offsite through open ditch and shallow groundwater pathways. Using the ensemble data the potential for soil N attenuation could be discriminated by 3 distinct groups reflecting the relative dominance of in situ N-biotransformation processes deduced from water composition: Group 1 (2 farms, ranked with high sustainability, NH4+ < 0.23 mg N/l, δ15N-NO3− > 5‰ and δ18O-NO3− > 10‰), low NH4+-N concentration coupled with a high denitrification potential; Group 2 (1 farm with moderate sustainability, NH4+ < 0.23 mg N/l, δ15N-NO3− < 8‰ and δ18O-NO3− < 8‰), low NH4+-N concentration with a high nitrification potential and a small component of complete denitrification; Group 3 (2 farms, ranked with low sustainability, NH4+ > 0.23 mg N/l, 14‰ > δ15N-NO3− > 5‰ and 25‰ > δ18O-NO3− > −2‰), high NH4+-N concentration due to low denitrification. The installation of a shallow drainage system (e.g. mole or gravel moles at 0.4 m depth) reduced the “net denitrification” ranking of a site, leading to water quality issues. From this detailed work an N sustainability tool for any site, which presents the relationship between drainage class, drainage design (if present), completeness of denitrification, rate of denitrification and NH4-N attenuation was developed. This tool allows a comparison or ranking of sites in terms of their N sustainability. The tool can also be used pre-land drainage and presents the consequences of future artificial land drainage on water quality and gaseous emissions at a given site.

Extreme oxygen dynamics in shallow water of a fully marine Irish sea lough

The benthos of Lough Hyne (Europe’s first marine reserve) in SW Ireland has changed dramatically in the past decade with declining invertebrate communities and proliferating ephemeral macroalgae. In summer 2011 and 2012, we measured dissolved oxygen (DO) levels on shallow subtidal rocky shores of the lough and recorded both benthic hypoxia (<2 mg O2 L−1) and hyperoxia (∼10–16 mg O2 L−1). In late summer 2013, we systematically characterized the spatial and temporal patterns of DO in the lough seawater. Daytime DO levels were hyperoxic either at or near the rocky shore, declined with increased distance for the first 5 m offshore, then stabilized at normoxic levels (∼8 mg O2 L−1). DO levels above and below rocks were variable and often showed large differences (max. difference of 15.6 mg O2 L−1), particularly at rocky shore sites with low current flow. At night, the DO in shallow water declined, becoming hypoxic to anoxic during calm weather. These extreme oxygen fluctuations (i) are amongst the first records to report severe conditions within Irish coastal waters and (ii) could contribute to the known recent decline in benthic invertebrate diversity within the marine reserve.

Biodiversity of shallow subtidal, under-rock invertebrates in Europe's first marine reserve: Effects of physical factors and scientific sampling

At Lough Hyne Marine Reserve in SW Ireland, shallow subtidal, under-rock biodiversity was investigated to assess (i) any deleterious effects of scientific sampling and (ii) quantitative baseline community patterns. Comparisons were made between 10 sites with annual rock-turning disturbance and 10 with multi-decadal (historical) disturbance. At each site, shallow subtidal rocks (N = 1289 total) were lifted, organisms recorded, and rocks replaced in their original position. Biodiversity indices were calculated to evaluate how diversity varied with location within the lough, frequency of sampling disturbance, degree of hypoxia/anoxia, dissolved oxygen (DO) concentration, and number of rocks turned. The richness of solitary invertebrates surveyed in situ averaged 21 taxa per site with significantly more in the South Basin (near the lough's connection to the ocean) than in the North Basin. The Shannon-Wiener Index did not differ significantly with variables investigated. However, evenness was higher at annually disturbed sites than at historical ones where anemones with algal symbionts often dominated. Several sites were hypoxic to anoxic under the shallow subtidal rocks. Cup corals were most abundant in the South Basin; DO was a crucial explanatory variable of these sensitive species. Solitary ascidians were most abundant at South-Basin annual sites with DO levels being a highly significant explanatory variable.