Browsing Marine Environment & Food Safety Services by Author "Bresnan, E."
Establishing boundary classes for the classification of UK marine waters using phytoplankton communitiesDevlin, 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.
Impacts of climate change on harmful algal bloomsBresnan, E.; Davidson, K.; Edwards, M.; Fernand, L.; Gowen, R.; Hall, A.; Kennington, K.; McKinney, A.; Milligan, S.; Raine, R.; et al. (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 ShelfSilke, 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.