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| Titel |
Physical controls on cold-water coral growth |
| VerfasserIn |
S. Floegel, A. Rueggeberg, C. Dullo  |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023448
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| Zusammenfassung |
| Along the Atlantic European continental margin, living cold-water coral reefs occur over a
wide bathymetric and hydrographical range. Focussing on two regions, the Celtic and the
Norwegian shelves we found that they are bound to different intermediate water masses.
Measurements of the physical and geological properties indicate that parameters such as
temperature, salinity, dissolved oxygen content, current intensities, and different substrates do
vary in a wide range without impacting the distribution of living cold-water coral reefs to a
first degree.
Our study shows that cold-water corals in the North Atlantic tolerate a wide range of
environmental conditions. The habitat of living reefs comprises a temperature-salinity field
with its lower boundary being equivalent to the Intermediate Salinity Maximum (ISM). The
ISM on the Celtic margin is represented by Mediterranean Outflow Water, while it is replaced
by Atlantic Water on the Norwegian margin. The upper limit corresponds to water mass
boundaries of Eastern North Atlantic Water / Mediterranean Outflow Water on the
Celtic margin and Norwegian Coastal Water / Atlantic Water on the Norwegian
margin.
The density of seawater is a frequently used parameter by oceanographers to describe and
understand ocean-mixing processes, as it is easier to mix water along a surface of constant
density (an ísopycnal´) rather than across it. The potential density anomaly sigma-theta is a
function of salinity, potential temperature, and pressure at the sea surface. This parameter
indicates values of sigma-theta = 27.35 - 27.65 kg m-3 for all living cold-water
coral reefs of the Porcupine Seabight, the Rockall Bank, and the Norwegian margin
highlighting the importance of physical boundary conditions on cold-water coral growth
and distribution. Additional information from literature shows that this value is
also valid for reef sites along the Western Atlantic (Nova Scotia, Florida Strait,
Brazilian margin) suggesting that this observation is an Atlantic-wide phenomenon. In
areas where coral growth is restricted to some small patches and reefs, or recent
mound growth is limited, like in the Gulf of Cadiz or off Mauritania, recent sigma
theta values lay outside the envelope of 27.5 ± 0.15 kg m-3. However, it has to be
mentioned that corals do not occur everywhere along the European continental
margins where sigma theta values are around 27.5 kg m-3. In this case, second
order parameters like sedimentation rates, currents, the lack or presence of good
settlement substrates, nutrient concentrations, etc. are controlling the coral growth and
settlement.
Literature
Dullo, W.-Chr., Flögel, S., Rüggeberg, A. (in press) Cold-water coral growth in relation to
the hydrography of the Celtic and Nordic European Continental Margin. Marine Ecology
Progress Series. |
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