Constraining past environmental changes of cold‐water coral mounds with geochemical proxies in corals and foraminifera

Raddatz, Jacek; Rüggeberg, Andres

doi:10.1002/dep2.98

Cited by 14 publications

(12 citation statements)

References 250 publications

(303 reference statements)

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“…Based on both hydrodynamic proxies, CWCs at Bowie Mound tend to accumulate during intervals with elevated flow speed. Phases of low flow speed are accompanied by low CWC abundances (e.g., at 140-150 and 465-550 cm), in line with the notion that active bottom currents play a significant role in distributing nutrients and food towards CWC colonies (e.g., Thiem et al, 2006;Dorschel et al, 2007;Davies et al, 2009;Raddatz et al, 2011). High current speeds will also increase sediment supply, thereby increasing accumulation rates due to the baffling capacity of CWC.…”

Section: Intermediate Water-mass Properties and Hydraulic Dynamicssupporting

confidence: 63%

“…Cold-water corals (CWCs) are hotspots of biodiversity in the deep-sea (Roberts and Cairns, 2014), important constituents of the deep-water carbon cycle (Lindberg and Mienert, 2005;Titschack et al, 2009Titschack et al, , 2015Titschack et al, , 2016White et al, 2012;Cathalot et al, 2015), and potent bioengineers due to their sediment-baffling capacity that allows for enormous sediment accumulation rates of up to 1500 cm kyr −1 during maximum CWC mound formation phases (Titschack et al, 2015;Titschack, 2017, Wienberg et al, 2018). Yet the impact of global climate change on CWC reefs and the associated ecosystems beneath them is poorly constrained because the factors driving or inhibiting their occurrence and the potential thresholds in their resilience to environmental change are still under debate (Hebbeln et al, 2019;Raddatz and Rüggeberg, 2019). Geological records reveal that coral mounds typically exhibit distinct phases of formation, often intercalated by intermittent periods of nondeposition and/or potentially erosion, indicating a high sensitivity of CWCs to changing boundary conditions (e.g., Rüggeberg et al, 2005;Kano et al, 2007;Frank et al, 2011;Raddatz et al, 2014Raddatz et al, , 2016Wienberg and Titschack, 2017;Wienberg et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Refined age model of core M125-34-2 from Bowie Mound. Panel (b) displays data from M125-34-2 on depth scale, comprising (A) CWC abundances (%; magenta) based on CT scanning and accumulation rates for both the Th/U-dated CWC-bearing intervals (black dashed lines; cf Raddatz et al, 2019). and the CWC-barren interval between 200 and 465 cm (dashed gray line); (B) blue arrows denote erosive horizons (hiatuses) E I -E IV (cf…”

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confidence: 99%

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Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

et al. 2020

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Abstract. Cold-water corals (CWCs) constitute important deep-water ecosystems that are under increasing environmental pressure due to ocean acidification and global warming. The sensitivity of these deep-water ecosystems to environmental change is demonstrated by abundant paleorecords drilled through CWC mounds that reveal characteristic alterations between rapid formation and dormant or erosive phases. Previous studies have identified several central parameters for driving or inhibiting CWC growth such as food supply, oxygenation, and the carbon saturation state of bottom water, yet there are still large uncertainties about the relative importance of the different environmental parameters. To advance this debate we have performed a multiproxy study on a sediment core retrieved from the 25 m high Bowie Mound, located at 866 m water depth on the continental slope off southeastern Brazil, a structure built up mainly by the CWC Solenosmilia variabilis. Our results indicate a multifactorial control on CWC growth at Bowie Mound during the past ∼ 160 kyr, which reveals distinct formation pulses during northern high-latitude glacial cold events (Heinrich stadials, HSs) largely associated with anomalously strong monsoonal rainfall over the continent. The ensuing enhanced runoff elevated the terrigenous nutrient and organic-matter supply to the continental margin and likely boosted marine productivity. The dispersal of food particles towards the CWC colonies during HSs 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, thereby aiding the concentration and along-slope dispersal of organic matter. Our study thus emphasizes the impact of continental climate variability on a highly vulnerable deep-marine ecosystem.

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Section: Intermediate Water-mass Properties and Hydraulic Dynamicssupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

et al. 2020

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“…Framework-building scleractinian cold-water corals (CWC) are one of the most important ecosystem engineers of the deep sea (e.g. Freiwald 2002;Roberts et al 2006;Frank et al 2011;Hebbeln et al 2019;Raddatz and Rüggeberg 2019). The initial settlement of CWCs generally occurs on continental slopes and shelves, seamounts or oceanic ridges (Roberts et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Solenosmilia variabilis-bearing cold-water coral mounds off Brazil

et al. 2019

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Cold-water corals (CWC), dominantly Desmophyllum pertusum (previously Lophelia pertusa), and their mounds have been in the focus of marine research during the last two decades; however, little is known about the mound-forming capacity of other CWC species. Here, we present new 230 Th/U age constraints of the relatively rarely studied framework-building CWC Solenosmilia variabilis from a mound structure off the Brazilian margin combined with computed tomography (CT) acquisition. Our results show that S. variabilis can also contribute to mound formation, but reveal coral-free intervals of hemipelagic sediment deposits, which is in contrast to most of the previously studied CWC mound structures. We demonstrate that S. variabilis only occurs in short episodes of \ 4 kyr characterized by a coral content of up to 31 vol%. In particular, it is possible to identify distinct clusters of enhanced aggradation rates (AR) between 54 and 80 cm ka-1. The determined AR are close to the maximal growth rates of individual S. variabilis specimens, but are still up to one order of magnitude smaller than the AR of D. pertusum mounds. Periods of enhanced S. variabilis AR predominantly fall into glacial periods and glacial terminations that were characterized by a 60-90 m lower sea Electronic supplementary material

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“…While growth patterns in reef forming CWCs are observable, the timing of their formation is unknown [17,18], making seasonal reconstructions challenging. In addition, commonly used proxies such as Mg/Ca and can be influenced by vital effects [19][20][21][22]. Other corals such as bamboo corals show more promising results regarding growth patterns and trace element proxies [23][24][25][26] and might therefore provide an alternative archive.…”

Section: Introductionmentioning

confidence: 99%

Compositional variability of Mg/Ca, Sr/Ca, and Na/Ca in the deep-sea bivalve Acesta excavata (Fabricius, 1779)

et al. 2021

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Acesta excavata (Fabricius, 1779) is a slow growing bivalve from the Limidae family and is often found associated with cold-water coral reefs along the European continental margin. Here we present the compositional variability of frequently used proxy elemental ratios (Mg/Ca, Sr/Ca, Na/Ca) measured by laser-ablation mass spectrometry (LA-ICP-MS) and compare it to in-situ recorded instrumental seawater parameters such as temperature and salinity. Shell Mg/Ca measured in the fibrous calcitic shell section was overall not correlated with seawater temperature or salinity; however, some samples show significant correlations with temperature with a sensitivity that was found to be unusually high in comparison to other marine organisms. Mg/Ca and Sr/Ca measured in the fibrous calcitic shell section display significant negative correlations with the linear extension rate of the shell, which indicates strong vital effects in these bivalves. Multiple linear regression analysis indicates that up to 79% of elemental variability is explicable with temperature and salinity as independent predictor values. Yet, the overall results clearly show that the application of Element/Ca (E/Ca) ratios in these bivalves to reconstruct past changes in temperature and salinity is likely to be complicated due to strong vital effects and the effects of organic material embedded in the shell. Therefore, we suggest to apply additional techniques, such as clumped isotopes, in order to exactly determine and quantify the underlying vital effects and possibly account for these. We found differences in the chemical composition between the two calcitic shell layers that are possibly explainable through differences of the crystal morphology. Sr/Ca ratios also appear to be partly controlled by the amount of magnesium, because the small magnesium ions bend the crystal lattice which increases the space for strontium incorporation. Oxidative cleaning with H2O2 did not significantly change the Mg/Ca and Sr/Ca composition of the shell. Na/Ca ratios decreased after the oxidative cleaning, which is most likely a leaching effect and not caused by the removal of organic matter.

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Constraining past environmental changes of cold‐water coral mounds with geochemical proxies in corals and foraminifera

Abstract: Cold-water coral (CWC) reefs and carbonate build-ups are abundant along the continental margins of the North and South Atlantic Ocean (

Cited by 14 publications

References 250 publications

Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

Solenosmilia variabilis-bearing cold-water coral mounds off Brazil

Compositional variability of Mg/Ca, Sr/Ca, and Na/Ca in the deep-sea bivalve Acesta excavata (Fabricius, 1779)

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