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Cold-water coral growth under extreme environmental conditions, the Cape Lookout area, NW Atlantic
Mienis, F.; Duineveld, G.C.A.; Davis, A.J.; Lavaleye, M.M.S.; Rosso, S.W.; Seim, H.; Bane, J.; van Haren, H.; Bergman, M.J.N.; de Haas, H.; Brooke, S.; van Weering, T.C.E. (2014). Cold-water coral growth under extreme environmental conditions, the Cape Lookout area, NW Atlantic. Biogeosciences 11: 2543-2560. hdl.handle.net/doi:10.5194/bg-11-2543-2014
In: Gattuso, J.P.; Kesselmeier, J. (Ed.) Biogeosciences. Copernicus Publications: Göttingen. ISSN 1726-4170, more
Peer reviewed article  

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Authors  Top 
  • Mienis, F., more
  • Duineveld, G.C.A., more
  • Davis, A.J.
  • Lavaleye, M.M.S., more
  • Rosso, S.W.
  • Seim, H.
  • Bane, J.
  • van Haren, H., more
  • Bergman, M.J.N., more
  • de Haas, H., more
  • Brooke, S.
  • van Weering, T.C.E., more

Abstract
    The Cape Lookout cold-water coral area off thecoast of North Carolina forms the shallowest and northernmostcold-water coral mound area on the Blake Plateau inthe NW Atlantic. Cold-water coral habitats near Cape Lookoutare occasionally bathed in the Gulf Stream, which is characterisedby oligotrophic warm water and strong surface currents.Here, we present the first insights into the mound distributionand morphology, sedimentary environment and coralcover and near-bed environmental conditions as recordedby bottom landers from this coral area. The mounds occurbetween 320 and 550m water depth and are characterisedby high acoustic backscatter indicating the presenceof hard structure. Three distinct mound morphologies wereobserved: (1) a mound with a flattened top at 320 m, (2)multi-summited mounds with a teardrop shape in the middlepart of the area and (3) a single mound at 540m water depth.Echosounder profiles show the presence of a strong reflectorunderneath all mound structures that forms the base of themounds. This reflector cropped out at the downstream side ofthe single mound and consists of carbonate slabs. Video analysisrevealed that all mounds are covered by Lophelia pertusaand that living colonies only occur close to the summitsof the SSW side of the mounds, which is the side that facesthe strongest currents. Off-mound areas were characterisedby low backscatter and sediment ripples, indicating the presenceof relatively strong bottom currents. Two bottom landerswere deployed amidst the coral mounds between December2009 and May 2010. Both landers recorded prominentevents, characterised by large fluctuations in environmentalconditions near the seabed as well as in the overlyingwater column. The period between December and April wascharacterised by several events of increasing temperature andsalinity, coinciding with increased flow and near-bed acousticbackscatter. During these events temperature fluctuatedby up to 9 ?C within a day, which is the largest temperaturevariability as measured so far in a cold-water coral habitat.Warm events, related to Gulf Stream meanders, had the durationof roughly 1 week and the current during these eventswas directed to the NNE. The consequences of such eventsmust be significant given the strong effects of temperature on the metabolism of cold-water corals. Furthermore, elevatedacoustic backscatter values and high mass fluxes werealso recorded during these events, indicating a second stressorthat may affect the corals. The abrasive nature of sand incombination with strong currents might sand blast the corals.We conclude that cold-water corals near Cape Lookout liveunder extreme conditions that limit mound growth at present.

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