Mid-Holocene extinction of cold-water corals off Namibia

Map of cold-water coral mounds

An exceptionally large cold-water coral mound province was discovered extending over 80 km along the Namibian shelf (offshore southwestern Africa) during the M122 Anna cruise on board RV Meteor. Anne-Marie Wefing and Rene Eichstädter from our team participated in this event in 2016 and Andrea Schröder-Ritzrau coordinated the subsequent effort in cold-water coral dating. The reefs have been found in shallow water depths of 160–270 m and this cold-water coral province comprises more than 2000 coral built mounds with heights of up to 20 m and constitutes the largest cold-water coral province known from the southeastern Atlantic Ocean. In Heidelberg we have conducted uranium-series dating, which revealed a short but intense pulse in coral mound formation during the early to mid-Holocene. Coral proliferation during this period was potentially supported by slightly enhanced dissolved oxygen concentrations compared to the present Benguela oxygen minimum zone (OMZ). The subsequent mid-Holocene strengthening of the Benguela Upwelling System and a simultaneous moderate northward migration of the Angola-Benguela Front resulted in an intensification of the OMZ that likely caused the sudden local extinction of the Namibian corals and prevented their reoccurrence until today. Read more about these findings in the recently published Geology article by Leonadro Tamborino and his co-workers (here). Further reading on the cold-water corals from Angola can be found in the article by Anne-Marie Wefing and her co-workers published in 2017 (here).