Auswirkungen von holozänen Änderungen der Wassermassenstruktur auf Kaltwasserkorallen-Ökosysteme am irischen Kontinentalhang
Zusammenfassung der Projektergebnisse
Within the frame of the DFG‐project CORICON, cold‐water coral mounds of the Belgica Mound Province (Porcupine Seabight, SW Ireland) and the adjacent slope area were studied with a focus on the recent coral occurrence and on the variability of mound growth and deposition pattern during the Late Pleistocene and Holocene. The outcomes of this project provide several new details on the depositional regime since the Late Pleistocene and revealed that previously postulated assumptions about the Belgica cold‐water coral province need to be partly revised. These are the highlights of our results: ∙ Detailed facies analyses based on ROV observations revealed occurrences of live cold‐water corals on coral mounds of the shallow Belgica mound chain comprising frequent to abundant colonies of Lophelia pertusa and Madrepora oculata. Therefore, former studies assuming that these mounds are mainly covered by coral rubble and dead coral framework, need to be revised. Live occurrences are restricted to the current‐exposed western flanks, the northern flanks and the top. They are often associated with large dunes, colonising the dune crests where they most likely benefit from the elevated position with enhanced current strength. ∙ A compilation of coral ages comprising newly obtained data (n=61) and data derived from literature revealed a striking depth‐dependent age pattern for the Belgica Mound Province during the Holocene. Whereas CWCs started to re‐colonise the deep Belgica mounds already directly after the Younger Dryas cold event at ~11.3 kyrs BP, the re‐colonisation of the shallow mounds was postponed starting at 8.6 krys BP. ∙ Deposition on the adjacent slope area ceased during the deglaciation, and the deposition of Holocene deposits (or even the erosion of late glacial deposits) was most likely prevented due to strong bottom currents which increased with the onset of the last deglaciation. Regarding the end of glacial deposition on the slope again a depth‐dependent pattern arises. Whereas deposition ceased for the deep slope (~990 m) already with the onset of deglaciation, the shallowest studied slope site (~740 m) revealed (de‐)glacial deposition until 15 kyrs BP. ∙ The depth‐dependent patterns which were observed for (a) the end of late glacial deposition on the slope with a postponed end of deposition for the upper slope and (b) the early Holocene re‐ colonisation of cold‐water corals mounds with a postponed onset of colonisation for the shallow mound chain provides the very first observation of a climate‐driven change in the vertical water mass structure having a direct impact on a deep‐sea ecosystem.
Projektbezogene Publikationen (Auswahl)
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(2010). Report and preliminary results of RV POSEIDON cruise POS400 "CORICON ‐ Cold‐water corals along the Irish continental margin", Vigo‐Cork, June 29‐July 15 2010. Berichte aus dem Fachbereich Geowissenschaften der Universität Bremen, No. 275, p. 46
Wienberg C and cruise participants
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Carbonate mound development in contrasting settings on the Irish margin. Deep‐Sea Research Part II (2013)
van der Land C, Eisele M, Mienis F, de Haas H, Hebbeln D, Reijmer JJG, van Weering TCE
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Sedimentation patterns on a cold‐water coral mound off Mauritania. Deep‐Sea Research Part II (2013)
Eisele M, Frank N, Wienberg C, Titschack J, Mienis F, Beuck L, Tisnerat‐Laborde N, Hebbeln D
