Solenosmilia variabilis-bearing cold-water coral mounds off Brazil

Abstract

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

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

“…After CT-scanning, the core was opened in frozen state (for details on the CT-scanning cf. Skornitzke et al,130 2019; Raddatz et al, 2020). Discrete samples for X-ray Diffractometry (XRD), grain-size analyses, C and N content, and stable carbon and oxygen isotope analyses of foraminifera and organic matter were taken from the sediment matrix https://doi.org/10.5194/bg-2020-206 Preprint.…”

“…Below the SMW, the SACW is found until 500 m water depth, characterized by decreasing temperatures and salinities (20ºC, 36.0 psu to 5ºC, 34.3 psu; Fig. 1) (Raddatz et al, 2020) owing to its formation in the southwest Atlantic and the South Indian Ocean (Sverdrup et al, 1942;Stramma and England, 1999). 95…”

“…The most common framework-forming CWC comprise preferences of S. variabilis, the dominant framework-building CWC discussed in this study, are still pending. Changes the species Lophelia pertusa (recently assigned to the genus Desmophyllum by Addamo et la., 2016), Macropora oculata, Solenosmilia variabilis,Bathelia candida,and 50 Enallopsammia profunda (e.g., Mangini et al, 2010;Frank et al, 2011;Muñoz et al, 2012;Hebbeln et al, 2014;Raddatz et al, 2020). Field and laboratory studies of L. pertusa, the most intensively investigated species, suggest that scleractinian CWC are non-specialists regarding food sources, which may range from POC to DOC (Kiriakoulakis et al, 2005;Duineveld et al, 2007;Gori et al, 2014;, algae, bacteria, and zooplankton (Gori et al, 2014;Mueller et al, 2014;Wienberg and Titschack, 2017).…”

“…To systematically test the relative importance of the diverse factors potentially influencing CWC growth and mound formation, we investigated the response of CWC at Bowie Mound, a coral-bearing mound in the Campos Basin on the continental slope offshore SE Brazil (Bahr et al, 2016;Raddatz et al, 2020) to changes in paleoenvironmental conditions. CWC-bearing mounds off Brazil were first reported by Viana et al (1998) and Sumida et al (2004) along 70 the continental slope at intermediate water depths between 500 to 1000 m within the Antarctic Intermediate Water (AAIW).…”

“…Major surface (red line), intermediate (green) and deep-water circulation features (blue) and water masses are indicated as well as the approximate location of the South Atlantic Convergence Zone (stippled line) as the main atmospheric feature. Inset shows a hydrographic section crossing the location of Bowie Mound core M125-34-2 with potential temperatures as 120 measured via CTD (black lines) during R/V METEOR Expedition M125 (Bahr et al, 2016;Raddatz et al, 2020); the location of the hydrographic section is indicated by a black line in the map.…”