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An overview of preliminary results from a series of recent Remotely Operated Vehicle (ROV) dives on the deep-water coral provinces of the Porcupine Bank, Irish continental margin, NE Atlantic is presented. The Porcupine Bank exhibits numerous giant carbonate mounds (up to 100s of metres in height) that occur predominantly, although not exclusively, on topographic ridges. The results revealed that, although these ridges have a tectonic origin, contemporaneous activity is typified by erosion due to strong hydrodynamic controls. The carbonate mounds are colonized by a variety of suspension feeders and associated fauna including framework-building corals (e.g., Lophelia pertusa and Madrepora oculata) although dense coral reef-like fauna coverage is not evident at present. The ecology of the carbonate mounds varied widely. Sessile megafauna, such as sponges, gorgonians and framework-building corals (e.g., Lophelia pertusa), were abundant on some of the carbonate mounds. Other mounds were relatively barren and appeared to be undergoing a natural senescence, with a much lower biomass of megafauna than is typical of shallow-water coral reefs. Some mounds had been damaged by demersal trawls, with smashed coral and lost gear common, whereas others appeared relatively pristine with occasional evidence of man-made litter. [ABSTRACT FROM AUTHOR]

The longest available time series on ocean currents indicates that the southward flow of water from the Greenland Sea is weakening, and that correlative large-amplitude changes have occurred in the rate of formation of intermediate Labrador Sea water. These have been linked to changes in regional climate which, if trends continue, could within 30 years alter the flow of the North Atlantic Drift and possibly interrupt the formation of Labrador Sea water, profoundly affecting regional climates, marine ecosystems and fisheries. We are attempting to use the carbonate skeletons of cold-water corals to find out how rapidly and how often the thermohaline circulation of the NE vs. NW Atlantic has changed in the past, just as tree rings and ice cores are used to investigate climate change on land. We have focussed on the NE Atlantic for our preliminary work, notably the Faroe-Shetland Channel: a major gateway between the Atlantic Ocean and the Norwegian Sea. Warm North Atlantic Drift water passes north through this channel on the surface, warming northern Europe. Cold Norwegian Sea Overflow Water returns at depth, contributing to the formation of North Atlantic Deep Water. Existing records are too short to allow conclusions regarding recent temporal changes in this inflow, so proxies are sought. We have analysed live-collected Lophelia pertusa skeletons collected in October 2001 using a ring dredge from RV Scotia along the worlds longest-running hydrographic transect (from 1893). Corals were sectioned using a slow-speed Isomet saw, and sampled for isotopic analysis using a Merchantek micromill. Observation of sectioned corals revealed dense-less dense couplets, as in every coral studied to date from tropical to deep cold-water environments worldwide. We sampled circumferentially, in the centres of individual bands, so as to produce temperature estimates using the “lines” technique of Smith et al. (2000). The results were simultaneously encouraging and confusing. Each of the coral samples generated lines from which temperatures could be estimated. Dense skeletal bands had lower temperatures than the less-dense bands, hence we conclude these were winter and summer bands, respectively. The mean annual temperature (MAT) range determined from one of the corals was 3.8°C. Pooling results from several corals yielded a lower estimate for MAT range: 2.3°C. The absolute temperatures from the corals, however, were somewhat lower than the instrumental record with “winter” records being more depleted than the “summer values”. This was unexpected and shows that determining detailed climate records from L. pertusa may be more difficult than hoped. [ABSTRACT FROM AUTHOR]

Deep-water corals are widespread in the North Atlantic. Colonial azooxanthellate scleractinians sustain ecosystems mostly in the bathyal zone down the slopes and oceanic banks off the Iberian Peninsula to as far north as the Scandinavian shelf off northern Norway. Estimates of the geological age of 37 deepwater corals exposed at the seabed from major reef areas in the North Atlantic were based on U/Th datings. In contrast to the purely Holocene ages of deep-water corals in Scandinavian waters, the Faroe area and the Rockall Trough, deep-water corals from lower latitudes like the seamounts off NW-Africa, the Mid-Atlantic Ridge and the western Mediterranean Sea seemed to have grown continuously over the last 50 ka. Overall, deep-water corals showed U/Th ages between 0.09 and 53.5 ka. [ABSTRACT FROM AUTHOR]