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| Titel |
Cold-water coral growth under extreme environmental conditions, the Cape Lookout area, NW Atlantic |
| VerfasserIn |
F. Mienis, G. C. A. Duineveld, A. J. Davies, M. M. S. Lavaleye, S. W. Ross, H. Seim, J. Bane, H. van Haren, M. J. N. Bergman, H. de Haas, S. Brooke, T. C. E. van Weering |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 9 ; Nr. 11, no. 9 (2014-05-13), S.2543-2560 |
| Datensatznummer |
250117399
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| Publikation (Nr.) |
 copernicus.org/bg-11-2543-2014.pdf |
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| Zusammenfassung |
| The Cape Lookout cold-water coral area off the coast of North Carolina forms
the shallowest and northernmost cold-water coral mound area on the Blake
Plateau in the NW Atlantic. Cold-water coral habitats near Cape Lookout are
occasionally bathed in the Gulf Stream, which is characterised by
oligotrophic warm water and strong surface currents. Here, we present the
first insights into the mound distribution and morphology, sedimentary
environment and coral cover and near-bed environmental conditions as recorded
by bottom landers from this coral area. The mounds occur between 320 and 550 m
water depth and are characterised by high acoustic backscatter indicating the
presence of hard structure. Three distinct mound morphologies were observed:
(1) a mound with a flattened top at 320 m, (2) multi-summited mounds with a
teardrop shape in the middle part of the area and (3) a single mound at
540 m water depth. Echosounder profiles show the presence of a strong
reflector underneath all mound structures that forms the base of the mounds.
This reflector cropped out at the downstream side of the single mound and
consists of carbonate slabs. Video analysis revealed that all mounds are
covered by Lophelia pertusa and that living colonies only occur
close to the summits of the SSW side of the mounds, which is the side that
faces the strongest currents. Off-mound areas were characterised by low
backscatter and sediment ripples, indicating the presence of relatively
strong bottom currents. Two bottom landers were deployed amidst the coral
mounds between December 2009 and May 2010. Both landers recorded prominent
events, characterised by large fluctuations in environmental conditions near
the seabed as well as in the overlying water column. The period between
December and April was characterised by several events of increasing
temperature and salinity, coinciding with increased flow and near-bed
acoustic backscatter. During these events temperature fluctuated by up to
9 °C within a day, which is the largest temperature variability as
measured so far in a cold-water coral habitat. Warm events, related to Gulf
Stream meanders, had the duration of roughly 1 week and the current during
these events was directed to the NNE. The consequences of such events must be
significant given the strong effects of temperature on the metabolism of
cold-water corals. Furthermore, elevated acoustic backscatter values and high
mass fluxes were also recorded during these events, indicating a second
stressor that may affect the corals. The abrasive nature of sand in
combination with strong currents might sand blast the corals. We conclude
that cold-water corals near Cape Lookout live under extreme conditions that
limit mound growth at present. |
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