Recent Submissions

  • Use of LC-MS testing to identify lipophilic toxins, to establish local trends and interspecies differences and to test the comparability of LC-MS testing with the mouse bioassay: an example from the Irish biotoxin monitoring programme 2001

    Hess, P.; McMahon, T.; Slattery, D.; Swords, D.; Dowling, G.; McCarron, M.; Clarke, D.; Gobbons, W.; Silke, J.; O'Cinneide, M. (Conselleria de Pesca e Asuntos Maritimos da Xunta de Galicia and Intergovernmental Oceanographic Commission of UNESCO, 2003)
    During 2001, the Marine Institute has extended its range of chemical tests to include the analysis of DSP toxins by Liquid Chromatography coupled to Mass Spectrometry (LC-MS). Thus the range of compounds determined extends from domoic acid over DSP compounds (okadaic acid and DTXs) to azaspiracids (AZAs). These tests complement the mouse bioassay, which is the current reference method for lipophilic toxins within the European Community. The development and performance characteristics of the LC-MS method are discussed. Isomer patterns and interspecies differences are discussed as well as local trends in time and variability at one production site at a given time. Comparison of the LC-MS results with the results from the mouse bioassay showed good agreement (93%), and a small but significant number of discrepancies (7%). Overall, the chemical testing has proven to be an invaluable tool in the assessment of shellfish toxicity in Ireland. Lacks of standards and reference materials are discussed as well as the need for further research into the equivalence of methods.
  • Establishing boundary classes for the classification of UK marine waters using phytoplankton communities

    Devlin, M.; Best, M.; Coates, D.; Bresnan, E.; O'Boyle, S.; Parke, R.; Silke, J.; Cusack, C.; Skeats, J. (Elsevier, 2007)
    This paper presents a description of three of the proposed phytoplankton indices under investigation as part of a classification framework for UK and ROI marine waters. The three indices proposed for the classification process are (i) phytoplankton biomass measured as chlorophyll, (ii) the frequency of elevated phytoplankton counts measuring individual species and total cell counts and (iii) seasonal progression of phytoplankton functional groups through the year. Phytoplankton biomass is calculated by a 90th percentile measurement of chlorophyll over the growing season (April to September) compared to a predetermined reference value. Calculation of functional groups and cell counts are taken as proportional counts derived from the presence of the indicator species or group as compared to the total phytoplankton count. Initial boundary conditions for the assessment of high/good status were tested for each index. Chlorophyll reference conditions were taken from thresholds developed for previous EU directives with the setting of offshore concentrations as a reference condition. Thresholds for elevated counts of phytoplankton taxa were taken from previous EU assessments describing counts that could be impact negatively on the environment. Reference seasonal growth curves are established using phytoplankton counts from ‘‘high status’’ waterbodies. To test the preliminary boundaries for each index, a risk assessment integrating nutrient enrichment and susceptibility for coastal and transitional waters was carried out to identify WFD waterbodies in England and Wales at different levels of risk. Waterbodies assessed as having low or medium risk from nutrient enrichment were identified as type 1 and type 2 waterbodies, and waterbodies assessed as high risk were identified as type 3 waterbodies. Phytoplankton data was extracted from the risk assigned waterbodies and applied to each phytoplankton index to test the robustness of the preliminary classification ranges for each phytoplankton index.
  • The use of immunoassay technology in the monitoring of algal biotoxins in farmed shellfish

    Wilson, A.; Keady, E.; Silke, J.; Raine, R. (International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO, 2013)
    The use of immunoassay technology as an adjunct method for monitoring biotoxins in shellfish was investigated at aquaculture sites in Killary Harbour, Ireland, during summer 2009. Sub-samples of mussels (Mytilus edulis) were taken from batches collected as part of the Irish National Phytoplankton and Biotoxin Monitoring Programme (NMP). Samples were analysed for Diarrhetic Shellfish Poisoning (DSP) toxins using a commercially available ELISA immunoassay kit. The results were compared with those obtained by chemical (liquid chromatography with mass spectrometry, LC-MS) and biological (mouse bioassay, MBA) methods from the monitoring programme. DSP levels increased in late June 2009 over the European Union maximum permitted level of 0.16 μg g-1 and positive MBA results led to harvest closures. This event was reflected in both the chemical and immunoassay results, where a positive relationship between them was found.
  • Irish National Phytoplankton Monitoring (Sites 41–45)

    Silke, J.; Cusack, C. (ICES, 2012)
    The Marine Institute in Ireland carries out a national phytoplankton monitoring programme which extends back to the late 1980s. This includes a harmful algal blooms (HABs) monitoring service that warns producers and consumers of concentrations of toxic plankton in Irish coastal waters that could contaminate shellfish or cause fish deaths. This programme is primarily located along the Atlantic seaboard and Celtic Sea. Scientists working on this monitoring programme have developed an understanding of phytoplankton populations and dynamics around the Irish coastline, especially in relation to those that cause shellfish toxicity. Particular emphasis is put on the detection and enumeration of harmful species. The importance of phytoplankton as an indicator of water quality is also studied and is a key component of the European Water Framework.
  • Overview of trends in plankton communities

    Licandro, P.; Head, E.; Gislason, A.; Benfield, M.C.; Harvey, M.; Margonski, P.; Silke, J. (ICES, 2011)
    Phytoplankton and zooplankton occupy pivotal positions within marine ecosystems. These small organisms fuel and support the foodwebs upon which almost all higher organisms depend. Fisheries and related economic activities are highly dependent on the production, size, and composition of zooplankton which, in turn, rely on primary production by phytoplankton. In addition to their role as prey for herbivorous zooplankton, phytoplankton absorb enormous quantities of dissolved CO2 via photosynthesis. Zooplankton then plays an essential role in the biological pump by consuming phytoplankton and transporting carbon from the upper ocean to the deep ocean, where it is sequestered for hundreds to thousands of years. Given the ecological and economic importance of phyto‐ and zooplankton, it is essential to understand and predict how they are likely to respond to climate change. Climate‐related hydrographic changes may also directly affect the abundance and composition of zooplankton, shifting the distribution of dominant species, changing the structure of the zooplankton community, and altering the timing, duration, and efficiency of zooplankton reproductive cycles. Ocean acidification through increased carbon dioxide dissolution in the upper ocean is lowering the pH in surface waters. A lower pH could impair the physiology and ultimately the abundance of many phytoplankton and zooplankton species. It is important to understand how phytoplankton and zooplankton are likely to respond to climate‐induced changes in the ocean. This section explores what is known about the sensitivity of phytoplankton and zooplankton to climate change and summarizes the trends that are evident in plankton communities within the ICES Area.
  • Small intestinal injuries in mice caused by a new toxin, Azaspiracid, isolated from Irish mussels

    Ito, E.; Satake, M.; Ofuji, K.; McMahon, T.; Silke, J.; James, K.; Yasumoto, T. (UNESCO, 2001)
    Pathological changes of the small intestine caused by a new toxin, azaspiracid, from Irish mussels were studied. Human poisoning cases included both diarrhetic shellfish and paralitic shellfish poisoning symptoms. The present paper focused on the former. Injuries were observed in the Upper part of the small intestine, where lamina propria in the villi became atrophied at the initial stage, followed by desquamation of epithelial cells and shortening of villi. The injuries were different from the DSP toxin okadaic acid; 1) they developed very slowly after a lag time of about 3 hr, 2) recovery was very late, 3) initial target and process were different.
  • Acidification and its effect on the ecosystems of the ICES Area

    Fernand, L.; LeQuesne, W.; Silke, J.; Li, B.; Kroeger, S.; Pinnegar, J.; Fossä, J.H.; Morán, X.A.G. (ICES, 2011)
    This focuses on the impacts of ocean acidification (OA) on ecosystems and higher trophic levels in the ICES Area. One of ICES distinguishing features is its access to scientists across the entire marine field. This report is based on the Report of the Workshop on the Significance of Changes in Surface CO2 and Ocean pH in ICES Shelf Sea Ecosystems (WKCpH; ICES, 2007c), updated to include recent research, using inputs from the chairs of ICES working groups. Oceanic uptake of atmospheric CO2 has led to a perturbation of the chemical environment, primarily in ocean surface waters, which is associated with an increase in dissolved inorganic carbon (DIC). The increase in atmospheric CO2 from ca. 280 ppmv (parts per million by volume) 200 years ago to 390 ppmv today (2011) has most probably been caused by an average reduction across the surface of the oceans of ca. 0.08 pH units (Caldeira and Wickett, 2003) and a decrease in the carbonate ion (CO32−) of ca. 20 μmol kg −1 (Keshgi, 1995; Figure 5.1). It has been estimated that the level could drop by a further 0.3 – 0.4 pH units by the year 2100 if CO2 emissions are not regulated (Caldeira and Wickett, 2003; Raven et al., 2005). A study of potential changes in most of the North Sea (Blackford and Gilbert, 2007) suggests that pH change this century may exceed its natural annual variability. Impacts of acidity induced change are likely, but their exact nature remains largely unknown, and they may occur across the whole range of ecosystem processes. Most work has concentrated on open‐ocean systems, and little research has been applied to the complex systems found in shelf‐sea environments.
  • Water Framework Directive: marine ecological tools for reference, intercalibration and classification (METRIC): final report for the ERTDI-funded project: 2005-W-MS-36

    Cusack, C.; O’Beirn, F.X.; King, J.J.; Silke, J.; Keirse, G.; Whyte, B.I.; Leahy, Y.; Noklegaard, T.; McCormack, E.; McDermott, G. (EPA, 2008)
    Water quality monitoring programmes exist in many of the Member States throughout the European Union (EU). With the implementation of the Water Framework Directive (WFD, Council Directive 2000/60/EC) all Member States must harmonise their national monitoring methods for each common metric (parameter indicative of a biological water quality element) used to determine the state of the aquatic environment to ensure consistent and comparable classification results for all biological community quality elements used (WFD Annex V, 1.4.1). The Marine Ecological Tools for Reference, Intercalibrationand Classification (METRIC) project, therefore, was designed specifically to support the Irish role in the EU Intercalibration Exercise of biological quality elements (BQEs) in order to set harmonised ecological quality criteria for the assessment of water quality in the transitional and coastal (TraC) waters of Europe. The BQEs investigated by METRIC included: Plants (phytoplankton, macroalgae andangiosperms), Benthic macroinvertebrates (soft-bottom habitat), Fish (estuarine).
  • New insights into the causes of human illness due to consumption of azaspiracid contaminated shellfish

    Chevallier, O.P.; Graham, S.F.; Alonso, E.; Duffy, C.; Silke, J.; Campbell, K.; Botana, L.M.; Elliott, C.T. (Nature Publishing Group, 2015)
    Azaspiracid (AZA) poisoning was unknown until 1995 when shellfish harvested in Ireland caused illness manifesting by vomiting and diarrhoea. Further in vivo/vitro studies showed neurotoxicity linked with AZA exposure. However, the biological target of the toxin which will help explain such potent neurological activity is still unknown. A region of Irish coastline was selected and shellfish were sampled and tested for AZA using mass spectrometry. An outbreak was identified in 2010 and samples collected before and after the contamination episode were compared for their metabolite profile using high resolution mass spectrometry. Twenty eight ions were identified at higher concentration in the contaminated samples. Stringent bioinformatic analysis revealed putative identifications for seven compounds including, glutarylcarnitine, a glutaric acid metabolite. Glutaric acid, the parent compound linked with human neurological manifestations was subjected to toxicological investigations but was found to have no specific effect on the sodium channel (as was the case with AZA). However in combination, glutaric acid (1mM) and azaspiracid (50nM) inhibited the activity of the sodium channel by over 50%. Glutaric acid was subsequently detected in all shellfish employed in the study. For the first time a viable mechanism for how AZA manifests itself as a toxin is presented.
  • Impacts of climate change on harmful algal blooms

    Bresnan, E.; Davidson, K.; Edwards, M.; Fernand, L.; Gowen, R.; Hall, A.; Kennington, K.; McKinney, A.; Milligan, S.; Raine, R.; Silke, J. (Marine Climate Change Impacts Partnership, 2013)
    High biomass Harmful Algal Blooms (HABs) such as Karenia mikimotoi and shellfish toxin producing HAB species continue to be observed in UK and Republic of Ireland waters. Regional differences continue to be seen in the distribution of HABs in UK and RoI waters with impacts mainly observed in the south and west coast of Ireland and regions in the UK with a strong Atlantic influence, e.g. Regions 1, 3, 4, 6 and 7. There is little monitoring aside from the continuous plankton recorder (CPR) in Region 8. The impacts from HABs in Wales, Northern Ireland and the Isle of Man are generally low. Since the last MCCIP report card was issued, blooms of Karenia mikimotoi have caused problems in Ayrshire, Scotland, and also in the north-west coast of Ireland where concerns about the quantity of dead wild fish washing on shore during an event in Ireland in 2012 resulted in two beaches being closed to the public. No clear trend that can be attributed to climate change can be observed in the incidence of shellfish toxin producing HABs since the last report card was issued. During the last two years the incidence of some shellfish toxins has continued to decrease (e.g. paralytic shellfish poisoning toxins in Scotland). High concentrations of yessotoxins (YTX) and azaspiracids (AZAs) have been recorded for the first time in Scotland. Northern Ireland enforced its first shellfish harvesting closure for high concentrations of domoic acid (the toxin responsible for amnesic shellfish poisoning, ASP) in 2012. A recent survey in Scottish waters (Regions 1, 6 and 7) has revealed the presence of domoic acid in the urine and faeces of harbour seals (Phoca vitulina). The impacts of these toxins on the health of marine mammals are unknown and a more detailed study is currently being undertaken. Many of the future impacts of climate change are unknown. Increasing sea surface temperatures as a result of climate change may increase the potential for blooms of species that are not currently found in UK and RoI waters through range expansion or human mediated introduction. There is evidence that no new HAB species have become established during the last two years. An increase in the duration of stratification of the water column may influence the abundance of HABs in UK and RoI waters. This is particularly relevant in shelf areas and Region 8, an area where offshore high biomass K. mikimotoi blooms have been hypothesized to initiate and impact coastal areas along the west of Ireland and Regions 6, 7 and 1. Conversely, an increase in wind speed and duration may reduce the duration of stratification in the water column. This may result in a decrease of some HAB dinoflagellate species and an increase in HAB diatom species. Little is known about the impacts of ocean acidification or changes in offshore circulation on the incidence of HABs. The role of offshore blooms in seeding coastal blooms (e.g. of K. mikimotoi) remains unknown and the lack of monitoring in Region 8 and on the shelf edge compounds this knowledge gap.
  • Phytoplankton and microbial plankton of the Northeast Atlantic Shelf

    Silke, J.; Kennington, K.; Bresnan, E.; Cusack, C. (ICES, 2012)
    The Northeast Atlantic Shelf region includes the sites from all coastal waters of Ireland, the Irish Sea, and western Scottish and Norwegian Sea waters. The region was defined by WGPME to include locations on the northern margin of Europe that were outside the North Sea/English Channel influence. The character of sites in the region are shallow, coastal-water sites ranging from sheltered bays on the south coast of Ireland and fjordic sea lochs of Scotland to fully exposed locations on the west coasts of Ireland and Scotland. Bathymetry of the region ranges from shallow embayments to regions of shallow, exposed continental-shelf waters. The topography of the shelf drops rapidly to 80–100 m within 20 km of the coast, where it extends to the shelf edge as a relatively flat plateau. Time-series of phytoplankton data from the Atlantic Shelf exhibit a typical seasonal pattern of temperate waters, with considerable geographical and temporal variation. The well-mixed winter conditions lead to a region-wide strong spring bloom observed at all sites. The ensuing decrease in nutrient levels lead to a variable summer period characterized by stratified conditions in coastal areas and periodic blooms of mixed or occasionally monospecific diatom and dinoflagellate composition. The growth period tails off in autumn, when a secondary bloom may occur in response to increased mixing and breakdown of the summer thermocline. The seasonal cycle returns to a quiescent winter phase, with generally mixed conditions, light limitation, and increased nutrients return. Seasonal stabilization and destabilization of the water column in this region accounts for most of the natural variation in both phytoplankton species composition and biomass.
  • Irish Shellfish Biotoxin Monitoring Programme

    Silke, J.; McMahon, T.; Hess, P. (Marine Institute, 2006)
    Since its initial development in the early 1970s the Irish aquaculture industry has grown to be an important contributor to the national economy. There has been a steady increase, in both output and value, as well as in job creation. The total production of farmed shellfish has increased from approximately 5,000 tonnes in 1980 to 44,678 tonnes in 2003 (Figure 1), with a first sale value of €41.8m and directly employing some 1100 people (Parsons et al, 2004). Mussels (Mytilus edulis), native oysters (Ostrea edulis), Pacific oysters (Crassostrea gigas), Clams (Tapes semidecussata) and scallops (Pecten maximus) are the main species produced. With a growing recognition and awareness internationally of the potential human health effects of the consumption of shellfish containing algal toxins, a monitoring programme was established in Ireland in the early 1980s and has continued since then. In this paper the evolution and development of the programme is described and discussed.
  • Harmful and nuisance algal blooms in Irish coastal waters 1990 - 1993

    Silke, J.; Jackson, D. (ICES, 1993)
    Algal blooms occur naturally around our coast. These high concentrations of planktonic algae are associated with favourable conditions of light and nutrients, and often occur at stratification/ mixing fronts. Many blooms are completely harmless, and form the diet of shellfish and zooplankton. Some colour the water red or brown. A few species are toxic and can cause fish kills or make shellfish unsafe to eat. The Fisheries Research Centre monitors phytoplankton in order to detect any toxic or potentially harmful blooms. The harmful and nuisance algal events from 1990 to 1993 are described.
  • 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
  • Performance of the EU Harmonised Mouse Bioassay for Lipophilic Toxins for the Detection of Azaspiracids in Naturally Contaminated Mussel (Mytilus edulis) Hepatopancreas Tissue Homogenates Characterised by Liquid Chromatography coupled to Tandem Mass Spectrometry

    Hess, P.; Butter, T.; Petersen, A.; Silke, J.; McMahon, T. (Elsevier, 2009)
    Azaspiracids (AZAs) are a group of lipophilic polyether toxins that were discovered in shellfish from Ireland in 1995, following a food poisoning incident. Both the limited availability of pure AZAs and the co-occurrence in shellfish of other toxins in combination with AZAs have so far prevented an in-depth evaluation of the performance of the EU reference test, the mouse bioassay (MBA), for this toxin group at the regulatory limit. The present study evaluated the performance of the mouse bioassay at the example of a mussel tissue homogenate, naturally contaminated with AZAs, diluted with uncontaminated tissues to appropriate concentration levels. Concentrations were determined using liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) (7 levels ranging from levels less than the limit of quantification to a maximum of ca. 2.24 mg/kg in hepatopancreas, which corresponds to a maximum whole flesh AZA1-equivalent of ca. 0.34 mg/kg). Replicate homogenates of each concentration level were analysed by MBA on 7 independent occasions over 6 weeks. Inhomogeneity between replicate aliquot portions was evaluated using LC-MS-MS and ranged from 1.8 to 6.6% RSD for the six levels contaminated above quantification limits. This variation was similar to the variability of the LC-MS-MS method within a batch, and the difference between replicate aliquots could thus be considered negligible. Other uncertainties considered in the study included the short- and long-term variability of the LC-MS-MS method, toxic equivalence factors, relative response factors in mass spectrometric detection, additional analogues and matrix effects. A concentration-response curve was modelled as a 4-parametric logistic fit to a sigmoidal function, with an LC50 of 0.70 mg AZA1-equivalent/kg hepatopancreas tissue. Furthermore, the mathematical model of the lethality data from this study suggests that occasional negative mouse assays at high concentrations, previously observed in the Irish statutory monitoring, are at least partly due to the biological variation of mice and can be understood on a statistical basis. The mathematical model of the concentration-response curve also describes the probability of a positive mouse bioassay at the current regulatory limit of 0.16 mg/kg to be ca. 95%. Therefore, it appears that the mouse bioassay performs very well in the implementation of this limit. Hence, the present study very strongly suggests that the MBA and LC-MS-MS techniques can be considered equivalent in the implementation of the current regulatory limit of 0.16 mg/kg for Azaspiracids in shellfish.
  • Monitoring of Shellfish Growing Areas - 1993

    Nixon, E.; Rowe, A.; Smith, M.; McLoughlin, D.; Silke, J. (Department of the Marine, 1994-08)
    During 1993, water and shellfish from 19 major growing areas were monitored for chemical parameters in accordance with the 1979 Council Directive 79/923/EC. At each site temperature, salinity, pH, dissolved oxygen and suspended solids measurements were taken and shellfish samples were returned to the laboratory for metal, chlorinated hydrocarbon and algal biotoxin determinations. Generally, water quality in all areas was good and conformed to the guidelines of the Directive. The highest levels of metals recorded were: cadmium in Tralee Bay (0.4 to 0.7µg/g) and Carlingford Lough (0.3 to 0.7µg/g) and lead in Wexford Harbour (0.5µg/g). Mercury in all cases was low with the exception of Cromane during November when levels of 0.3µg/g were detected. Chlorinated hydrocarbons levels were extremely low and indicate the clean nature of Irish shellfish, unpolluted by these synthetic organic compounds. Algal biotoxins were not detected in any samples.
  • Proceedings of the 8th Irish Shellfish Safety Workshop

    McMahon, T.; Deegan, B.; Silke, J.; Ó Cinneide, M. (Marine Institute, 2008)
    This document outlines the proceedings of the 8th Irish Shellfish Safety Scientific Workshop. This event was organised by the Marine Institute, the Food Safety Authority of Ireland and Bord Iascaigh Mhara to discuss the methods and advances of food safety with respect to shellfish health.
  • Proceedings of the 9th Irish Shellfish Safety Scientific Workshop

    Gilmartin, M.; Silke, J. (Marine Institute, 2009)
    The 9th Irish Shellfish Safety Workshop was held on the 20th March, 2009, in Kenmare, County Kerry. The Workshop was co-sponsored by the Marine Institute, Bord Iascaigh Mhara, the Food Safety Authority of Ireland, and the Sea Fisheries Protection Authority, with support from IFA Aquaculture. The topics addressed at the workshop included an update on the National Biotoxin monitoring programme, and a number of research projects with Irish participation and international perspectives on toxin detection. Finding mechanisms to improve our product was a common theme with presentations on improving food safety, increasing productivity, providing easily applied test methods, and research in support of the shellfish industry. The focus of the three Workshop sessions was on a review of the year, research and legislation.