Monsoonal forcing controlled cold water coral growth off south-eastern Brazil during the past 160 kyrs

Abstract

Abstract. Cold-water corals (CWC) constitute important deep-water ecosystems that are increasingly under environmental pressure due to ocean acidification and global warming. The sensitivity of these deep-water ecosystems to environmental change is demonstrated by abundant paleo-records drilled through CWC mounds that reveal a characteristic alteration between rapid formation and dormant or erosive phases. Previous studies have identified several parameters such as food supply, oxygenation, and carbon saturation state of bottom water as central for driving or inhibiting CWC growth, yet there is still a large uncertainty about the relative importance of the different environmental parameters. To advance this debate we have performed a multi-proxy study on a sediment core retrieved from the 25 m high Bowie Mound, located in 866 m water depth on the continental slope off south-eastern Brazil, a structure built up mainly by the CWC Solenosmilia variabilis. Our results indicate a multi-factorial control on CWC growth and mound formation at Bowie Mound during the past ~160 kyrs, which reveals distinct formation pulses during glacial high northern latitude cold events (Heinrich Stadials, HS) largely associated with anomalous continental wet periods. The ensuing enhanced run-off elevated the terrigenous nutrient and organic matter supply to the continental margin, and might have boosted marine productivity. The dispersal of food particles towards the CWC colonies during HS was facilitated by the highly dynamic hydraulic conditions along the continental slope that prevailed throughout glacial periods. These conditions caused the emplacement of a pronounced nepheloid layer above Bowie Mound aiding the concentration and along-slope dispersal of organic matter. Our study thus demonstrates a yet unrecognized impact of continental climate variability on a highly vulnerable deep-marine ecosystem.

Spatiotemporal Discharge Variability of the Doce River in SE Brazil During MIS 6 and 5

“…Furthermore, (aragonitic) scleractinian cold water corals are presently growing at around 900 m water depth. These corals even profited from strong runoff and higher nutrient availability during glacial periods (Bahr et al, 2020;Raddatz et al, 2020). We therefore assume a low aragonite solubility at the deposition site during both glacial and interglacial periods as well as low dissolution in the water column.…”

Benthic foraminiferal faunas associated with cold‐water coral environments in the North Atlantic realm

“…Yet, since CWCs show a discontinuous growth which follows climate cycles, CWC mounds often present a cyclic aggradation interrupted by numerous hiatuses (Dorschel et al, 2005b;Frank et al, 2009;Matos et al, 2017;Stalder et al, 2018;Thierens et al, 2013). To overcome this discontinuous nature of CWC mound records, a twofold approach investigating both cores recovered from the coral mound and from the off-mound contouritic sediments surrounding the coral mounds has been used to reconstruct past environmental conditions (Bahr et al, 2020;Dorschel et al, 2005b;Eisele et al, 2011;Huvenne et al, 2009b;Matos et al, 2017;Rüggeberg et al, 2007;Wang et al, 2019). Theoretically, this strategy allows the discontinuous record provided by CWC mounds to be completed by a more continuous off-mound contourite record.…”

Deep-sea coral Lophelia pertusa laboratory maintenance and exposure to barite using water recirculation systems

“…However, there are fewer studies that have focused on deep-sea corals in the Southern Hemisphere compared to those in the Northern Hemisphere. Although studies have been conducted on the Brazilian coast (Viana et al, 1998;Le Goff-Vitry et al, 2004;Pires et al, 2004;Sumida et al, 2004;Castro et al, 2006;Kitahara, 2007;Pires, 2007;Arantes et al, 2009;Kitahara et al, 2009;Cordeiro et al, 2012;Bahr et al, 2020), most have focused on specific taxa or on a compilation of azooxanthellate stony corals, and no studies have focused on maintaining deep-sea corals in the laboratory and subsequent experimentation.…”