March 31st, 2008 |
I’m in Carvoerio, Portugal presenting work done on the EU FP7 project HERMES regarding food supply mechanisms to a coral reef. Read the abstract below:
Internal waves provide a food supply mechanism for cold-water coral reefs
Andrew J. Davies, Marc Lavaleye, Magda Bergman, J. Murray Roberts, Hans Van Haren and Gerard Duineveld
The cold-water coral Lophelia pertusa forms large biogenic reefs throughout the North Atlantic Ocean. The mechanics of food supply to these areas have been largely hypothesised, with topographical focussing of currents, breaking internal waves and retained matter above banks all put forward as potential mechanisms. However, at present, there has only been limited description of these processes from detailed in situ observations. During several HERMES cruises, numerous physical and biological observations have been made in the Mingulay Reef complex. Located between the Outer Hebridean Island chain and the Scottish Mainland, this reef complex is situated within a dynamic area with semi-diurnal tides and currents of up to 80 cm s-1. In 2006 and 2007, multiple deployments of landers, recording moorings, ship mounted ADCP and CTDs were used to record the food supply processes and the physical habitat of the L. pertusa reefs in the area. The complex topography of the area retains a solitary internal wave which breaks as direction of the tide changes. The wave drives surface productivity and warmer waters to the reef in a regular pattern. This mechanism has a strong resemblance with the theory of Frederiksen et al (1992) that coral distribution could be in areas where the bottom slope is critical to semi-diurnal internal waves.
March 21st, 2008 |
Marine ecology, Publications
Andrew J. Davies and Mark P. Johnson
Published in Estuarine, Coastal and Shelf Science (2006)
Both climate change and the North Atlantic Oscillation (NAO) may influence coastal systems by altering wave exposure. The effects of such climatic forcing are often coherent over relatively large geographic areas. Temporal trends in wave exposure at any particular shore are, however, the result of an interaction between site-specific fetch characteristics and changes in wind climate. This leads to contrasting trends in wave exposure at locations separated by no more than a few kilometres. Wave exposures were estimated at locations around a sea lough over 32 years to characterise these scales of variability. Locations separated by approximately 5 km had independent dynamics with respect to the temporal trend (correlation range -0.35 to 0.44) and to associations with the NAO (correlation range -0.18 to 0.40). Wave exposure can therefore be increasing for a section of shore while nearby areas have the opposite trend. Mean exposure at a location was not a good predictor of the temporal trend. More exposed sites were, however, sensitive to variations in the strength of the NAO. The reduction of large scale forcing to small-scale variability has implications for the detection and mitigation of potential climate change impacts.
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Davies, A.J. & Johnson, M.P. (2006) “Coastline configuration disrupts large-scale climatic forcing, leading to divergent temporal trends in wave exposure” Estuarine and Coastal Shelf Science 69 (3-4): 643-648.