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Menai Bridge, United Kingdom

Dausse A.,Bangor University | Garbutt A.,UK Center for Ecology and Hydrology | Norman L.,Bangor University | Papadimitriou S.,Bangor University | And 4 more authors.
Estuarine, Coastal and Shelf Science

Depending on their location along an estuarine salinity gradient, tidal marshes are thought to have different impacts on the chemical composition of the water during flooding. However, there is a lack of direct measurements of fluxes occurring between the marsh surface and the water column to corroborate this hypothesis. This study compared fluxes of nutrient and dissolved organic carbon (DOC) between the water column and the marsh surface and the emission of greenhouse gases, at four sites located along the salinity gradient of an estuary of north-western Wales (UK). The exchanges of dissolved organic carbon and nitrogen (DON), dissolved inorganic nitrogen (DIN), soluble reactive phosphorus and silicic acid, carbon dioxide, methane and nitrous oxide were measured during tidal inundation in May and September 2008 using in situ incubation chambers. There was no linear pattern along the salinity gradient and the concentration of nutrients and DOC in the flood water did not appear to control the biogeochemical processes driving the marsh surface/water column exchanges in the studied marshes. Multivariate analysis showed a clear discrimination in functioning between sites with the fresh and brackish marshes having a more similar functioning compared to low and middle marshes. The main differences between these two groupings were in the fluxes of DOC and nitrate. The phenology of plant species, soil organic matter content and soil oxygenation appear be the dominant factors explaining the observed fluxes. © 2012 Elsevier Ltd. Source

Timko P.G.,Center for Applied Marine science | Timko P.G.,University of Michigan | Arbic B.K.,University of Michigan | Richman J.G.,U.S. Navy | And 4 more authors.
Journal of Geophysical Research: Oceans

We present and apply several skill tests to assess tidal currents generated within a global ocean model compared to an archive of current meter records spanning 40years. Within the North Atlantic we have identified over 1800 velocity records available for comparison to model output. The skill tests identify those regions where tidal ellipse parameters (semi-major/minor axis, inclination and Greenwich phase) fall within 95% confidence intervals derived from observations. Additional skill tests examine the vertical and horizontal structure of the tidal currents using the correlation and root mean square error between the observations and model. The skill tests account for grid misrepresentation within the model by comparing model values in a local 9-point neighborhood. Both the three-dimensional structure of model tidal currents and barotropic model tidal currents are compared to the altimetry based barotropic model TPXO 7.2. Our results indicate that the non-data assimilative ocean model performance is comparable to TPXO 7.2. The semi-major axes of the semi-diurnal constituents lie within the 95% confidence intervals between 40% and 60% of the time in some regions of the North Atlantic. The performance degrades when all tidal ellipse parameters are considered. Root mean square errors between the model and observations distributed through the water column are generally less than 1cm s-1 representing an error of less than ∼10% for constituent M2. The model tides also exhibit high correlation with observations in the horizontal planes. The skill tests could be adapted to other sets of observations and other models. © 2012. American Geophysical Union. All Rights Reserved. Source

Lallias D.,Bangor University | Lallias D.,Center for Applied Marine science | Boudry P.,French Research Institute for Exploitation of the Sea | Lapegue S.,French Research Institute for Exploitation of the Sea | And 3 more authors.
Conservation Genetics

The native European flat oyster Ostrea edulis is listed in the OSPAR Convention for the Protection of the Marine Environment of the North-East Atlantic (species and habitat protection) and in the UK Biodiversity Action Plan. Once extremely abundant in the nineteenth century, European stocks of O. edulis have declined during the twentieth century to rare, small, localised populations due to overexploitation, habitat degradation and, most recently, the parasitic disease bonamiosis. Selective breeding programmes for resistance to bonamiosis have been initiated in France and Ireland. High genetic diversity and bonamiosis-resistance would be important features of any sustainable restoration programmes for O. edulis. Oysters were sampled across Europe from four hatchery sources, four pond-cultured sources and four wild, but managed fisheries and were genotyped at five microsatellite loci. Hatchery-produced populations from small numbers of broodstock showed a significant loss of genetic diversity relative to wild populations and pedigree reconstruction revealed that they were each composed of a single large full-sib family and several small full-sib families. This extremely low effective population size highlights the variance in reproductive success among the potential breeders. Pond-cultured oysters were intermediate in genetic diversity and effective population size between hatchery and wild populations. Controlled hatchery production allows the development of bonamiosis-resistant strains, but at the expense of genetic diversity. Large scale pond culture on the other hand can provide a good level of genetic diversity. A mixture of these two approaches is required to ensure a healthy and sustainable restoration programme for O. edulis in Europe. © 2010 Springer Science+Business Media B.V. Source

Cotter E.,University College Cork | Malham S.K.,Center for Applied Marine science | O'Keeffe S.,University College Cork | Lynch S.A.,University College Cork | And 4 more authors.

Though many studies have been carried out on mortality events in Crassostrea gigas this is the first study of the phenomenon in the Irish Sea. Unexplained summer mortalities have been taking place in C. gigas populations in Ireland since the 1990's. Production of this species currently occurs at low levels in Wales, with no reports of unusual mortalities and, as similar environmental factors and husbandry techniques exist in both countries, a comprehensive investigation into mortalities in Ireland was considered to be beneficial to the industry in that country but applicable to growers in Wales also. A single cohort of C. gigas was obtained from a hatchery in both 2003 and 2004, and performance was compared over the summer months of both years following relaying at sites in Ireland and Wales. Oyster growth, condition, biochemical content and gonad development were examined and the influence of these parameters on summer mortality was investigated. Oysters were sampled every second week. Significant mortalities occurred at the Irish sites during the study but not at the Welsh sites. Oysters at the Irish sites displayed significantly increased growth, condition and gonad development compared to oysters at the Welsh sites. Both protein and glycogen levels were higher in the oysters held at the Irish sites than in the Welsh sites. Differences in the measured parameters between the two sites were greater in 2003, when temperatures were higher, than in 2004. Fast growth rates, gonadal development and spawning may contribute to increased physiological stress in young oysters making them more susceptible to mortalities during the summer months. This study indicated that site-related differences, such as environmental parameters, have a significant effect on subsequent performance of oysters and, may strongly influence mortality rates. © 2010 Elsevier B.V. All rights reserved. Source

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