Marine Environment and Health Series: Recent submissions
Now showing items 41-46 of 46
-
Monitoring of zebra mussels in the Shannon-Boyle navigation, otherThe zebra mussel (Dreissena polymorpha) population has been closely monitored in Ireland following its discovery in 1997. The species has spread from lower Lough Derg, where it was first introduced, to most of the navigable areas of the Shannon and other interconnected navigable waters. This study took place in the summers of 2000 and 2001 and investigated the relative abundance and biomass of zebra mussels found in the main navigations of the Shannon and elsewhere in rivers, canals and lakes where colonisation was likely. During 2000 zebra mussels were found for the first time in Carnadoe, Kilglas and Grange Loughs on the River Shannon. In 2001, they were discovered on the Ballinasloe Navigation at Poulboy Lough and in Ballinasloe Harbour. For the first time outside of the Shannon-Boyle navigation, established populations were discovered in Garadice Lough on the Shannon-Erne Waterway and in Ringsend Basin and Tullamore Harbour on the Grand Canal. Zebra mussels continue to have their greatest densities in lakes and large reservoirs of the Shannon-Boyle navigation. A maximum biomass of 4.1kg per sq.m was recorded in Lough Key. No zebra mussel larvae or their attached stages were found in the larger lakes outside of the Shannon-Boyle and Erne Navigations. Larvae were found however, in Tullamore Harbour for the first time. In separate studies approximately two hundred adults were found in Lough Bo, Co. Sligo and less than ten specimens were found in Lough Gill, Co. Sligo. The only living population of native freshwater mussels (Anodonta spp.) presently known in the lake regions of the Shannon is in the Carnadoe Cut, between Carnadoe Lough and Kilglas Lough. This population of Anodonta spp. is fouled with zebra mussels. Freshwater mussels were also found in Garadice Lough and Assaroe Reservoir. These were also fouled with zebra mussels.
-
Winter Nutrient Monitoring of the Western Irish Sea – 1990 to 2000Winter nutrient concentrations in the western Irish Sea have been monitored annually from 1990 to 2000. Surface samples have been taken between Dundalk Bay and Carnsore Point and analysed for total oxidised nitrogen (TOxN), ortho-phosphate (ortho-P), silicate and salinity. More recently monitoring has been extended into the Celtic Sea. Data from this monitoring programme are presented in detail, along with comparisons to existing data sets. The spatial distribution of nutrients and salinity are presented for each year in contour or classed plots (depending on sample coverage for the particular year). Salinity values were representative of those expected in the Irish Sea and TOxN, ortho-P and silicate values were in general agreement with previous studies. A short summary of studies on nutrient levels in estuaries on the western Irish Sea is presented. In addition, riverine input data supplied by the Environmental Protection Agency (EPA) is used to evaluate the relative magnitude of nutrient inputs from riverine and oceanic sources. Nutrient concentrations are considered using an ecological quality objectives (EcoQOs) approach, proposed as part of the Oslo Paris Convention’s (OSPAR) ‘Common Procedure for Identification of the Eutrophication Status of the Maritime Area’, in partial consideration of the trophic status of the western Irish Sea. Although there is evidence for nutrient enrichment in some estuarine waters and possibly to a lesser extent in some coastal waters, there is little evidence for generally elevated nutrient levels in coastal and offshore waters in the western Irish Sea. Salinity regression curves were calculated for TOxN and ortho-P values in order to generate salinity-normalised concentrations for trend determinations. Regression and trend analysis were carried out on the sample area as a whole and also on regions defining the north, mid, and south western Irish Sea. Trend analysis has been performed, based on nutrient-salinity regressions, using Trend-Y-Tector. A decrease in TOxN over the study period (ranging from 4 to13%) is observed in all regions analysed with the exception of the south west Irish Sea, where a 5% increase was indicated. Analysis of trends in ortho-P concentration showing decreasing trends ranging from 20 to 33%. On visual examination, trends in TOxN are not as intuitively apparent as trends in ortho-P concentrations, therefore it may not be prudent to draw conclusions from them at this stage. Trend analysis of riverine inputs shows an increase in TOxN by 17% and no apparent trend in ortho-P levels. These trends are not consistent with trends observed in the Irish Sea. On the basis of this assessment, it is recommended that this monitoring be continued. The design of future nutrient monitoring surveys is considered, with a view to improving the efficacy of the monitoring regime.
-
The fate of oxytetracycline in the marine environment of a salmon cage farmThis paper gives a summary of previously published results of studies on the dispersal of oxytetracycline from the vicinity of a typical salmon farm. These studies showed the environmental impact of occasional treatments to be negligible. Concentrations of oxytetracycline (OTC) were measured in the benthic sediments and in mussel Mytilus edulis sampled in the vicinity of an inshore salmon farm on the west coast of Ireland. Concentrations between 1.0 μg/g and 14.7 μg/g were observed in sediments within 120 m from the farm. Concentrations declined exponentially with time, reaching low levels after 32 days and reduced to traces at 66 days. The highest concentrations were observed in the top 2 cm of sediment, falling to trace levels at a depth of 10 cm. The half-life of OTC persistence in mussels was found to be approximately 2 days. Residues in unpolluted sediment beneath the cages were never present in high concentrations and were flushed out rapidly. In the presence of excessive quantities of unconsumed food pellets on the seabed and in anoxic sediment, the persistence of OTC was significantly prolonged. Monitoring the quality of the sediment could therefore provide adequate indication of any risk of accumulation of antibiotic, without the need for elaborate chemical analyses. Residues in sediment, invertebrates and salmon could account for not more than 1.3% of total input of OTC. It was concluded that the antibiotic was very rapidly dispersed in the environment and its use in salmon therapy posed no material risk to human or environmental health.
-
Trace Metal and Chlorinated Hydrocarbon Concentrations in Shellfish from Irish Waters, 1997-1999In accordance with the monitoring requirements of Council Directive 79/923/EEC, on the quality required of shellfish waters, and Council Directive 91/492/EEC, laying down the health conditions for the production and placing on the market of live bivalve molluscs, the Marine Institute collected water and shellfish samples from major shellfish growing areas and analysed for physicochemical parameters, trace metal levels and chlorinated hydrocarbon concentrations. Since, with the exception of mercury, there are no currently applicable European standards for the concentration of these contaminants in shellfish, the levels were compared with the available standards and guidance values for human consumption, as compiled by the Oslo and Paris Commission (OSPAR) countries. As in previous years, the water quality from shellfish growing areas was good and conformed to the guidelines and requirements of the Directive. Petroleum hydrocarbons were not observed in any of the shellfish waters or as deposits on the shellfish. Chlorinated hydrocarbon levels were very low, evidence of the clean, unpolluted nature of Irish shellfish and shellfish producing waters. Trace metal levels were consistently low with the exception of cadmium in oyster tissue, which was slightly elevated in the 1999 samples from Clew Bay, Inner Tralee Bay, Aughinish Limerick and Kilkieran. However these levels did not exceed the Dutch human consumption standard value or the EU maximum limit of 1.0 mg/kg wet weight due to apply from 2002. This survey confirms previous studies which show Irish shellfish products are effectively free from trace metal and chlorinated hydrocarbon contamination.
-
An Assessment of Water Quality Data from Kilkieran Bay, Co. GalwayA programme monitoring water quality was carried out at 11 sites in Kilkieran Bay, Co. Galway from 1984 to the 1998, for the most part. Continuous monthly readings were recorded at 5 of these sites. Three sites were sampled for temperature, salinity, nitrate, nitrite and phosphate. Three replicate samples were taken at each sampling event. While salinity remained relatively stable throughout, temperature varied considerably between winter and summer months (e.g. Lettercallow, 3.5-18.5ºC), at each of the sites. Nutrient levels were highest in winter months at all sites. The innermost sites tended to have lower salinities and lower nutrient levels. However, there were no statistical differences in nutrient levels among the sites and from year to year. These findings suggest that there was no appreciable increase (or decrease) in nutrient loading within Kilkieran Bay. It is recommended that sampling within the bay is defined according to the broad geographic regions outlined and that intensive sampling was not necessary.
-
Proceedings of the 9th Irish Shellfish Safety Scientific WorkshopThe 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.
