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  • A Low-Complexity Mosaicing Algorithm for Stock Assessment of Seabed-Burrowing Species

    Corrigan, D.; Sooknanan, K.; Doyle, J.; Lordan, C.; Kokaram, A. (IEEE Xplore, 2018)
    This paper proposes an algorithm for mosaicing videos generated during stock assessment of seabed-burrowing species. In these surveys, video transects of the seabed are captured and the population is estimated by counting the number of burrows in the video. The mosaicing algorithm is designed to process a large amount of video data and summarize the relevant features for the survey in a single image. Hence, the algorithm is designed to be computationally inexpensive while maintaining a high degree of robustness. We adopt a registration algorithm that employs a simple translational motion model and generates a mapping to the mosaic coordinate system using a concatenation of frame-by-frame homographies. A temporal smoothness prior is used in a maximum a posteriori homography estimation algorithm to reduce noise in the motion parameters in images with small amounts of texture detail. A multiband blending scheme renders the mosaic and is optimized for the application requirements. Tests on a large data set show that the algorithm is robust enough to allow the use of mosaics as a medium for burrow counting. This will increase the verifiability of the stock assessments as well as generate a ground truth data set for the learning of an automated burrow counting algorithm.
  • Seabird movement reveals the ecological footprint of fishing vessels

    Bodey, T.W.; Jessopp, M.J.; Votier, S.C.; Gerritsen, H.D.; Cleasby, I.R.; Hamer, K.C.; Patrick, S.C.; Wakefield, E.D.; Bearhop, S. (Cell Press, 2014)
    Exploitation of the seas is currently unsustainable, with increasing demand for marine resources placing intense pressure on the Earth’s largest ecosystem [1]. The scale of anthropogenic effects varies from local to entire ocean basins 1, 2 and 3. For example, discards of commercial capture fisheries can have both positive and negative impacts on scavengers at the population and community-level 2, 3, 4, 5 and 6, although this is driven by individual foraging behaviour 3 and 7. Currently, we have little understanding of the scale at which individual animals initiate such behaviours. We use the known interaction between fisheries and a wide-ranging seabird, the Northern gannet Morus bassanus [3], to investigate how fishing vessels affect individual birds’ behaviours in near real-time. We document the footprint of fishing vessels’ (≥15 m length) influence on foraging decisions (≤11 km), and a potential underlying behavioural mechanism, by revealing how birds respond differently to vessels depending on gear type and activity. Such influences have important implications for fisheries, including the proposed discard ban [8]), and wider marine management.
  • Estimating biomass, fishing mortality, and “total allowable discards” for surveyed non-target fish

    Shephard, S.; Reid, D.G.; Gerritsen, H.D.; Farnsworth, K.D. (Oxford University Press, 2014)
    Demersal fisheries targeting a few high-value species often catch and discard other “non-target” species. It is difficult to quantify the impact of this incidental mortality when population biomass of a non-target species is unknown. We calculate biomass for 14 demersal fish species in ICES Area VIIg (Celtic Sea) by applying species- and length-based catchability corrections to catch records from the Irish Groundfish Survey (IGFS). We then combine these biomass estimates with records of commercial discards (and landings for marketable non-target species) to calculate annual harvesting rates (HR) for each study species. Uncertainty is incorporated into estimates of both biomass and HR. Our survey-based HR estimates for cod and whiting compared well with HR-converted fishing mortality (F) estimates from analytical assessments for these two stocks. Of the non-target species tested, red gurnard (Chelidonichthys cuculus) recorded some annual HRs greater than those for cod or whiting; challenging “Pope's postulate” that F on non-target stocks in an assemblage will not exceed that on target stocks. We relate HR for each species to two corresponding maximum sustainable yield (MSY) reference levels; six non-target species (including three ray species) show annual HRs ≥ HRMSY. This result suggests that it may not be possible to conserve vulnerable non-target species when F is coupled to that of target species. Based on biomass, HR, and HRMSY, we estimate “total allowable catch” for each non-target species.
  • The response of North Atlantic diadromous fish to multiple stressors including land use change: a multidecadal study

    de Eyto, E.; Dalton, C.; Dillane, M.; Jennings, E.; McGinnity, P.; O'Dwyer, B.; Poole, R.; Rogan, G.; Taylor, D. (NRC Research Press, 2016)
    Reduction of freshwater habitat quality due to land use change can have significant impacts on diadromous fish. Partitioning this impact from other potential drivers, such as changing marine conditions and climate, is hampered by a lack of long term datasets. Here, four decades of data were used to assess the impact of land use change on <i>Salmo salar</i> L. and anadromous <i>Salmo trutta</i> L. in the Burrishoole catchment, Ireland, one of the few index sites for diadromous fish in the North Atlantic. Land use change was found to have no significant impact on the freshwater survival of either salmon or trout. However, climate impacted significantly on the survival of salmon and trout in freshwater, with poor survival in years with wetter warmer winters, coinciding with positive North Atlantic Oscillation values. Additionally, cold springs were associated with higher survival in trout. The addition of hatchery salmon into the salmon spawning cohort coincided with low freshwater survival. Our results highlight the necessity for a broad ecosystem approach in any conservation effort of these species.
  • Diel Surface Temperature Range Scales with Lake Size

    Woolway, R.I.; Jones, I.D.; Maberly, S.C.; French, J.R.; Livingstone, D.M; Monteith, D.T; Simpson, G.L.; Thackeray, S.J.; Andersen, M.R.; Battarbee, R.W.; DeGasperi, C.L.; Evans, C.D.; de Eyto, E.; Feuchtmayr, H.; Hamilton, D.P.; Kernan, M.; Krokowski, J.; Rimmer, A.; Rose, K.C.; Rusak, J.A.; Ryves, D.B.; Scott, D.R.; Shilland, E.M.; Smyth, R.L.; Staehr, P.A.; Thomas, R.; Waldron, S.; Weyhenmeyer, G.A. (PLoS ONE, 2016)
    Ecological and biogeochemical processes in lakes are strongly dependent upon water temperature. Long-term surface warming of many lakes is unequivocal, but little is known about the comparative magnitude of temperature variation at diel timescales, due to a lack of appropriately resolved data. Here we quantify the pattern and magnitude of diel temperature variability of surface waters using high-frequency data from 100 lakes. We show that the near-surface diel temperature range can be substantial in summer relative to long-term change and, for lakes smaller than 3 km2, increases sharply and predictably with decreasing lake area. Most small lakes included in this study experience average summer diel ranges in their near-surface temperatures of between 4 and 7°C. Large diel temperature fluctuations in the majority of lakes undoubtedly influence their structure, function and role in biogeochemical cycles, but the full implications remain largely unexplored.
  • Rapid and highly variable warming of lake surface waters around the globe

    O'Reilly, C.M.; Sharma, S.; Gray, D.K.; Hampton, S.E.; Read, J.S.; Rowley, R.J.; Schneider, P.; Lenters, J.D.; McIntyre, P.B.; Kraemer, B.J.; Wayhenmeyer, G.A; Straile, D.; Dong, B.; Adrian, R.; Allan, M.G.; Anneville, O.; Arvola, L.; Austin, J.; Bailey, J.L.; Baron, J.S.; Brookes, J.D.; de Eyto, E.; Dokulil, M.T.; Hamilton, D.T.; Havens, K.; Hetherington, A.L.; Higgins, S.N.; Hook, S.; Izmest'eva, L.R.; Joehnk, K.D.; Kangur, K.; Kasprzak, P.; Kumagai, M.; Kuusisto, E.; Leshkevich, G.; Livingstone, D.M.; MacIntyre, S.; May, L.; Melack, J.M.; Mueller-Navarra, D.C.; Naumenko, M; Noges, P.; Noges, T.; North, R.P.; Plisnier, P.D.; Rigosi, A.; Rimmer, A.; Rogora, M.; Rudstam, L.G.; Rusak, J.A.; Salmaso, N.; Samal, N.R.; Schindler, D.E.; Schladow, S.G.; Schmid, M.; Schmidt, S.R.; Silow, E.; Soylu, M.E.; Teubner, K.; Verburg, P.; Voutilainen, A.; Watkinson, A.; Williamson, C.E.; Zhang, G. (American Geophysical Union, 2015)
    In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade 1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, leading to the counterintuitive result that regional consistency in lake warming is the exception, rather than the rule. The most rapidly warming lakes are widely geographically distributed, and their warming is associated with interactions among different climatic factors —from seasonally ice-covered lakes in areas where temperature and solar radiation are increasing while cloud cover is diminishing (0.72°C decade 1) to ice-free lakes experiencing increases in air temperature and solar radiation (0.53°C decade 1). The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.
  • Spatial Segregation within the Spawning Migration of North Eastern Atlantic Mackerel (Scomber scombrus) as Indicated by Juvenile Growth Patterns

    Jansen, T.; Campbell, A.; Brunel, T.; Worsøe Clausen, L. (PLoS ONE, 2013)
    A comparison of growth data (fish length) with latitude shows that southern juvenile mackerel attain a greater length than those originating from further north before growth ceases during their first winter. A similar significant relationship was found between the growth in the first year (derived from the otolith inner winter ring) and latitude for adult mackerel spawning between 44uN (Bay of Biscay) and 54uN (west of Ireland). These observations are consistent with spatial segregation of the spawning migration; the further north that the fish were hatched, the further north they will tend to spawn. No such relationship was found in mackerel spawning at more northerly latitudes, possibly as a consequence of increased spatial mixing in a more energetic regime with stronger currents. This study provides previously lacking support for spawning segregation behaviour among North East Atlantic mackerel – an important step towards understanding the migratory behaviour of mackerel and hence the spatiotemporal distribution dynamics around spawning time.
  • Identification and Characterization of Cyprinid Herpesvirus-3 (CyHV-3) Encoded MicroRNAs

    Donohoe, O. H.; Henshilwood, K.; Way, K.; Hakimjavadi, R.; Stone, D. M.; Walls, D. (PLoS ONE, 2015)
    MicroRNAs (miRNAs) are a class of small non-coding RNAs involved in post-transcriptional gene regulation. Some viruses encode their own miRNAs and these are increasingly being recognized as important modulators of viral and host gene expression. Cyprinid herpesvirus 3 (CyHV-3) is a highly pathogenic agent that causes acute mass mortalities in carp (Cyprinus carpio carpio) and koi (Cyprinus carpio koi) worldwide. Here, bioinformatic analyses of the CyHV-3 genome suggested the presence of non-conserved precursor miRNA (pre-miRNA) genes. Deep sequencing of small RNA fractions prepared from in vitro CyHV-3 infections led to the identification of potential miRNAs and miRNA–offset RNAs (moRNAs) derived from some bioinformatically predicted pre-miRNAs. DNA microarray hybridization analysis, Northern blotting and stem-loop RT-qPCR were then used to definitively confirm that CyHV-3 expresses two pre-miRNAs during infection in vitro. The evidence also suggested the presence of an additional four high-probability and two putative viral pre-miRNAs. MiRNAs from the two confirmed pre-miRNAs were also detected in gill tissue from CyHV-3-infected carp. We also present evidence that one confirmed miRNA can regulate the expression of a putative CyHV-3-encoded dUTPase. Candidate homologues of some CyHV-3 pre-miRNAs were identified in CyHV-1 and CyHV-2. This is the first report of miRNA and moRNA genes encoded by members of the Alloherpesviridae family, a group distantly related to the Herpesviridae family. The discovery of these novel CyHV-3 genes may help further our understanding of the biology of this economically important virus and their encoded miRNAs may have potential as biomarkers for the diagnosis of latent CyHV-3.
  • The recent population expansion of boarfish, Capros aper (Linnaeus, 1758): interactions of climate, growth and recruitment

    Coad, J.O.; Hüssy, K.; Farrell, E.D.; Clarke, M.W. (John Wiley & Sons, Inc, 2014)
    The objectives of this study were to evaluate whether temperature changes in the Northeast Atlantic influence the growth and recruitment dynamics of boarfish, Capros aper. Two geographically separate areas were examined, ‘north’ at the northern distribution range west of Ireland and ‘south’ on the main fishing grounds south of Ireland. No significant differences in length-at-age were observed between the two areas. Interannual otolith growth patterns were similar between the two areas with distinct years of faster and slower growth. In the ‘north’, no significant relationship between adult growth and temperature was observed, while growth in the ‘south’ was positively related to temperature up to approximately 16°C growth rates were suppressed in the years with temperatures above that. Recruitment showed a positive correlation with adult growth the previous year for the Spanish recruitment index only, suggesting spatial connectivity between the Celtic Sea and the Bay of Biscay. The age distributions were similar in both areas and despite the boarfish's longevity of >30 years, are dominated by the age classes corresponding to the years with high recruitment, suggesting that increased recruitment is responsible for the observed stock expansion.
  • Managing a complex population structure: exploring the importance of information from fisheries-independent sources

    Hintzen, N.T.; Roel, B.; Benden, D.; Clarke, M.; Egan, A.; Nash, R.D.M.; Rohlf, N.; Hatfield, E.M.C. (Oxford University Press, 2014)
    Natural resource managers aim to manage fish stocks at sustainable levels. Often, management of these stocks is based on the results of analytical stock assessments. Accurate catch data, which can be attributed to a specific population unit and reflects the population structure, are needed for these approaches. Often though, the quality of the catch data is compromised when dealing with a complex population structure where fish of different population units mix in a fishery. The herring population units west of the British Isles are prone to mixing. Here, the inability to perfectly allocate the fish caught to the population unit they originate from, due to classification problems, poses problems for management. These mixing proportions are often unknown; therefore, we use simulation modelling combined with management strategy evaluation to evaluate the role fisheries-independent surveys can play in an assessment to provide unbiased results, irrespective of population unit mixing and classification success. We show that failure to account for mixing is one of the major drivers of biased estimates of population abundance, affecting biomass reference points and MSY targets. When mixing of population units occurs, the role a survey can play to provide unbiased assessment results is limited. Either different assessment models should be employed or stock status should be considered from the survey data alone. In addition, correctly classifying the origin of fish is especially important for those population units that are markedly smaller in size than other units in the population complex. Without high classification success rates, smaller population units are extremely vulnerable to overexploitation.
  • Where the lake meets the sea: strong reproductive isolation is associated with adaptive divergence between lake resident and anadromous three-spined sticklebacks

    Ravinet, M.; Hynes, R.; Poole, R.; Cross, T.F.; McGinnity, P.; Harrod, C.; Prodöhl, P.A. (PLoS ONE, 2015)
    Contact zones between divergent forms of the same species are often characterised by high levels of phenotypic diversity over small geographic distances. What processes are involved in generating such high phenotypic diversity? One possibility is that introgression and recombination between divergent forms in contact zones results in greater phenotypic and genetic polymorphism. Alternatively, strong reproductive isolation between forms may maintain distinct phenotypes, preventing homogenisation by gene flow. Contact zones between divergent freshwater-resident and anadromous stickleback (Gasterosteus aculeatus L.) forms are numerous and common throughout the species distribution, offering an opportunity to examine these contrasting hypotheses in greater detail. This study reports on an interesting new contact zone located in a tidally influenced lake catchment in western Ireland, characterised by high polymorphism for lateral plate phenotypes. Using neutral and QTL-linked microsatellite markers, we tested whether the high diversity observed in this contact zone arose as a result of introgression or reproductive isolation between divergent forms: we found strong support for the latter hypothesis. Three phenotypic and genetic clusters were identified, consistent with two divergent resident forms and a distinct anadromous completely plated population that migrates in and out of the system. Given the strong neutral differentiation detected between all three morphotypes (mean FST = 0.12), we hypothesised that divergent selection between forms maintains reproductive isolation. We found a correlation between neutral genetic and adaptive genetic differentiation that support this. While strong associations between QTL linked markers and phenotypes were also observed in this wild population, our results support the suggestion that such associations may be more complex in some Atlantic populations compared to those in the Pacific. These findings provide an important foundation for future work investigating the dynamics of gene flow and adaptive divergence in this newly discovered stickleback contact zone.
  • Dissolved azaspiracids are absorbed and metabolized by blue mussels (Mytilus edulis)

    Jauffrais, T.; Kilcoyne, J.; Herrenknecht, C.; Truquet, P.; Séchet, V.; Miles, C.O.; Hess, P. (Elsevier, 2013)
    The relationship between azaspiracid shellfish poisoning and a small dinoflagellate, Azadinium spinosum, has been shown recently. The organism produces AZA1 and -2, while AZA3 and other analogues are metabolic products formed in shellfish. We evaluated whether mussels were capable of accumulating dissolved AZA1 and -2, and compared the toxin profiles of these mussels at 24 h with profiles of those exposed to live or lysed A. spinosum. We also assessed the possibility of preparative production of AZA metabolites by exposing mussels to semi-purified AZA1. We exposed mussels to similar concentration of AZAs: dissolved AZA1 + 2 (crude extract) at 7.5 and 0.75 μg L−1, dissolved AZA1+2 (7.5 μg L−1) in combination with Isochrysis affinis galbana, and lysed and live A. spinosum cells at 1 × 105 and 1 × 104 cell mL−1 (containing equivalent amounts of AZA1 + 2). Subsequently, we dissected and analysed digestive glands, gills and remaining flesh. Mussels (whole flesh) accumulated AZAs to levels above the regulatory limit, except at the lower levels of dissolved AZAs. The toxin profile of the mussels varied significantly with treatment. The gills contained 42–46% and the digestive glands 23–24% of the total toxin load using dissolved AZAs, compared to 3–12% and 75–90%, respectively, in mussels exposed to live A. spinosum. Exposure of mussels to semi-purified AZA1 produced the metabolites AZA17 (16.5%) and AZA3 (1.7%) after 4 days of exposure, but the conversion efficiency was too low to justify using this procedure for preparative isolation.
  • Bioactive agents from marine mussels and their effects on human health

    Grienke, U.; Silke, J.; Tasdemir, D. (Elsevier, 2014)
    The consumption of marine mussels as popular seafood has increased steadily over the past decades. Awareness of mussel derived molecules, that promote health, has contributed to extensive research efforts in that field. This review highlights the bioactive potential of mussel components from species of the genus Mytilus (e.g. M. edulis) and Perna (e.g. P. canaliculus). In particular, the bioactivity related to three major chemical classes of mussel primary metabolites, i.e. proteins, lipids, and carbohydrates, is evaluated. Within the group of proteins the focus is mainly on mussel peptides e.g. those obtained by bio-transformation processes, such as fermentation. In addition, mussel lipids, comprising polyunsaturated fatty acids (PUFAs), are discussed as compounds that are well known for prevention and treatment of rheumatoid arthritis (RA). Within the third group of carbohydrates, mussel polysaccharides are investigated. Furthermore, the importance of monitoring the mussel as food material in respect to contaminations with natural toxins produced by microalgae is discussed
  • Assessment of biomarkers in Mytilus edulis to determine Good Environmental Status for implementation of MSFD in Ireland

    Giltrap, M.; Ronan, J.; Hardenberg, S.; Parkes, G.; McHugh, B.; McGovern, E.; Wilson, J.G. (Elsevier, 2013)
    Candidate OSPAR/ICES recommended biomarkers at the level of the individual in Mytilus edulis for determination of good environmental status for MSFD were evaluated against contaminant levels at sites around Ireland. The sites chosen ranged from moderate to low pollution levels, but the actual ranking of the sites varied according to the contaminant levels present. At the most contaminated site, Cork, 4 out of 16 contaminants exceeded the EAC, while at Shannon, no EACs were exceeded. The SOS assay suggested that Cork was the healthiest site with a LT50 of 17.6 days, while SOS for Shannon was 15.6 days. Likewise, condition factors varied among sites and did not always correspond to contaminant-based status. There may be uncertainty in assigning status around the not good:good boundary. This raises potential difficulties not only in the biomarker/contaminant load relationship but also in the reliability of the biomarkers themselves and hence barriers meeting compliance levels.
  • Environmental factors associated with invasion: modeling occurrence data from a coordinated sampling programme for Pacific oysters

    Kochmann, J.; O’Beirn, F.X.; Yearsley, J.; Crowe, T.P. (Springer Netherlands, 2013)
    Documenting establishment and spread of invasive species requires extensive co-ordinated sampling programmes. Identifying the factors promoting or inhibiting local establishment of an invasive species can improve capacity to predict further spread and underpin strategies to limit spread. Here, a structured sampling programme was used to assess the current distribution of feral populations of Pacific oysters, Crassostrea gigas, in Ireland. Sixty-nine sites were sampled using a standardised protocol combining semi-quantitative and quantitative approaches. Sites were chosen to represent variation in proximity to aquaculture and a range of environmental variables. Oyster populations were found at 18 locations, with densities ranging from single individuals to nine individuals per m2. The broad size range of oysters found is indicative of more than one recruitment event. Logistic regression indicated that feral oysters were positively associated with the presence of hard substrata or biogenic reef, long residence times of embayments and large intertidal areas. There was also a tendency for oysters to occur disproportionately in bays with aquaculture, but >500 m from it. Small-scale analysis within sites showed that oysters were almost exclusively attached to hard substrata and mussel shell. The approach taken here provides a rigorous repeatable methodology for future monitoring and a detailed basis for the prediction of further spread.
  • Defining value per unit effort in mixed métier fisheries

    Davies, S.; Minto, C.; Officer, R.; Lordan, C. (Elsevier, 2015)
    Value achieved from time spent at sea is a central driver of fishing decisions and fishing behaviors. Value per unit effort (VPUE) is an important indicator of economic performance in itself and a useful metric within integrated mixed fisheries models. A time series of Irish first sale prices and total per trip landings values (VPT) highlight heterogeneity in fish prices and VPTs achieved by the Irish fleet spatially and temporally, as well as variability with species targeting. This investigation compared models to standardize fishing trip VPUE accounting for species targeting (métier groupings), engine power (a kW proxy for vessel size), seasonal and annual variability, fishing effort, and individual vessels (encompassing variability in vessel characteristics and skipper effects). Linear mixed effects models incorporating random vessel effects and within-group variance between métier groupings performed best at describing the variability in the dataset. All investigated factors were important in explaining variability, and thus important in standardizing VPUE. Models incorporating fishing days (days with reported fishing activity) and engine power as separate variables resulted in improved AIC values. Therefore, fishing days were considered to be the most appropriate effort measure to generate VPUE. The effort unit traditionally applied in measures of per unit effort, fishing hours, performed comparatively poorly in relation to VPT.
  • Anthropocene environmental change in an internationally important oligotrophic catchment on the Atlantic seaboard of western Europe

    Dalton, C; O'Dwyer, B; Taylor, D; DeEyto, E; Jennings, E; Chen, G; Poole, R; Dillane, M; McGinnity, P (Elsevier, 2014)
    Oligotrophic catchments with short spatey streams, upland lakes and peaty soils characterise northwest European Atlantic coastal regions. These catchments are important biodiversity refuges, particularly for sensitive diadromous fish populations but are subject to changes in land use and land management practices associated with afforestation, agriculture and rural development. Quantification of the degree of catchment degradation resulting from such anthropogenic impacts is often limited by a lack of long-term baseline data in what are generally relatively isolated, poorly studied catchments. This research uses a combination of palaeolimnological (radiometrically-dated variations in sedimentary geochemical elements, pollen, diatoms and remains of cladocera), census, and instrumental data, along with hindcast estimates to quantify environmental changes and their aquatic impacts since the late 19th century. The most likely drivers of any change are also identified. Results confirm an aquatic biotic response (phyto- and zooplankton) to soil erosion and nutrient enrichment associated with the onset of commercial conifer afforestation, effects that were subsequently enhanced as a result of increased overgrazing in the catchment and, possibly, climate warming. The implications for the health of aquatic resources in the catchment are discussed
  • Spatial and seasonal variation of peatland-fed riverine macroinvertebrate and benthic diatom assemblages and implications for assessment: a case study from Ireland

    O’Driscoll, C.; de Eyto, E.; Rodgers, M.; O’Connor, M.; Asam, Z-u-Z; Kelly, M.; Xiao, L. (Springer, 2014)
    Blanket peat catchments are important biodiversity refugia. Key pressures on peatland catchment water bodies include artificial drainage, forestry, over-grazing, wind farm development and climate change, and assessment of these pressures requires sensitive monitoring programmes. This study, undertaken in two neighbouring blanket peat catchments, examined the variability in macroinvertebrate and diatom assemblages and related indices in response to spatial and seasonal variability. Multivariate analysis revealed significant trends in the taxa distribution of both groups and the indices downstream and away from the constraining influence of the peat. However, the ecological quality ratios and status assessments for the associated water bodies were consistent irrespective of spatial variability in assemblages and raw indices. Significant seasonal trends emerged only in the macroinvertebrate assemblages and indices. This study contributes to the understanding of sources of uncertainty in ecological assessment and thus provides valuable information for the calibration of assessment protocols for sensitive peatland catchments.
  • Whole-tree harvesting and grass seeding as potential mitigation methods for phosphorus export in peatland catchments

    O'Driscoll, Connie; O'Connor, Mark; Asam, Zaki-ul-Zaman; DeEyto, Elvira; Poole, Russell; Rodgers, Michael; Zhan, Xinmin; Nieminen, Mika; Xiao, Liwen (Elsevier, 2014)
    Forest clearfelling is potentially a major environmental problem with respect to the degradation of water quality in receiving water courses due to phosphorus (P) release from soil and clearfelling residue stocks. Recent studies have highlighted the need to investigate the performance and benefits of potential mitigation methods such as whole tree harvesting (WTH) and grass seeding. In this study, fifteen plots (0.014 ha each) were constructed in a standing coniferous forest and P concentrations in plot runoff were monitored for one year prior to clearfelling. Following clearfelling three replicates of five forest harvesting management practices/treatments were applied to the plots: brash with grass seeding (Treatment 1), brash (Treatment 2), brash mat/ tree extraction route (Treatment 3), WTH (Treatment 4) and WTH with grass seeding (Treatment 5). These treatments were designed to comparatively assess the benefits of WTH and grass seeding practices on mitigating P released from forested peatlands following clearfelling and to determine the sources and sinks of P following clearfelling operations. Annual average total reactive phosphorus (TRP) concentrations in the plot runoff were < 20 µg L-1 in all treatments before clearfelling, and increased to 79 µg L-1, 160 µg L-1, 335 µg L-1, 50 µg L-1 and 38 µg L-1 in Treatments 1, 2, 3, 4 and 5, respectively, after clearfelling. These results highlight that WTH and grass seeding can be used efficiently as methods to improve water quality, aiding in the protection of the biota residing in the aquatic systems draining peatland catchments.
  • A multi-proxy palaeolimnological study to reconstruct the evolution of a coastal brackish lake (Lough Furnace, Ireland) during the late Holocene

    Cassina, Filippo; Dalton, Catherine; Dillane, Mary; De Eyto, Elvira; Poole, Russell; Sparber, Karin (Elsevier, 2013)
    This study examines the evolution of Lough Furnace, a coastal brackish lake in the west of Ireland, using high-resolution sensors in the water column and palaeolimnological examination of the sediment archive. Palaeoenvironmental reconstructions suggest that meromixis formed as a result of sea level rise prior to ca. 4000 cal. yr BP. Increased seawater inflow has progressively led to permanent water stratification, which caused the onset of anoxia, making the monimolimnion a harsh environment for biological life. Diatom floristic interpretations suggest a progressive upcore increase in salinity, which is paralleled by a reduction in cladocera remains. Diagenetic processes have not altered the sediment organic matter signature. Organic matter mainly derives from freshwater DOC and appears to be linked to the presence of peat bogs in the catchment as confirmed by the C/N ratio. Upcore variations in the C/N ratio with a ca. 800-year periodicity have been interpreted as the result of alternating dry and wet climatic phases during the late Holocene, which appear synchronous with the NAO and long-term solar cycles. The current hydrology is largely controlled by freshwater inflow, which determines permanent meromictic conditions. Overturns are rare, requiring a specific combination of factors such as exceptionally dry and warm summers followed by cool autumns. According to the climate projections for the next century in Ireland, permanent meromictic conditions will probably continue.

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