<rahmann et al. 
the purpose of these paleoceanographic studies, long gravity 
cores were recovered during four scientific expeditions (M77/1, 
M77/2, M92, and M135; see Figure 8). During the cruises 
M77/1 and M77/2 in 2008, 51 sediment cores were retrieved 
below and in the centre of the OMZ, from —17° S to the 
equator (see Figure 8). Most of the records collected in 
the core of the OMZ (ie., —200 to —500 m depth), from 
=8 to 15° S, show sedimentary discontinuities during the 
Holocene (last 11700 years), which preclude high resolution 
paleoceanographic reconstructions in this area (Salvatteci et al., 
2014, 2016; Erdem et al., 2016). Based on the information 
collected during M77/1 and M77/2 and also on the scientific 
literature, cruise M135 aimed specifically at finding the 
most complete Holocene sequence in the Eastern Tropical 
South Pacific. For this purpose, a detailed paleoceanographic 
survey took place at —17° S, an area that is less affected 
by processes that can produce sediment discontinuities. Six 
sediment cores were retrieved, two of which contained the 
most complete sediment sequences for the last 10000 years 
(Salvatteci et al., 2019). 
Data from the gravity and piston cores collected during 
cruises M77/1, M77/2, M92, and M135 have been assembled by 
Salvatteci and Mehrtens (2021d); see Table 2 and Supplementary 
Table 24. A piston corer was used on cruise M77/2 while on 
M77/1, M92, and M135 a long gravity corer was employed. 
[n total, 57 sediment cores were collected on the four cruises. 
The water depths of the sampling sites ranged from 144 to 
2591 m; however, most of the cores were retrieved in the core 
of the OMZ, ie., between —200 and —700 m depth. The average 
sediment recovery of the piston cores was 1168 cm. For the 
gravity cores, the average sediment recovery was 318 cm for 
M77/1 and 609 cm for M135. At the time of writing, these 
sediment cores have been used in 17 scientific publications that 
aim to understand climate and ocean variability and its effect 
on the OMZ at multiple timescales (Salvatteci and Mehrtens, 
2021d; see Table 2 and Supplementary Table 24). Age models 
(Salvatteci and Mehrtens, 2021a; see Table 2 and Supplementary 
Table 25), X-Ray Fluorescence (XRF) measurements (Salvatteci 
ınd Mehrtens, 2021c; see Table 2 and Supplementary Table 26), 
and other geochemical records (Salvatteci and Mehrtens, 2021b; 
see Table 2 and Supplementary Table 27) have been assembled 
and published. In addition, core tops of near sediment surface 
cores from multiple-corers (MUCs) have been used to establish 
local calibrations for several paleoproxies, such as redox- 
sensitive elements in foraminifera (i.e., Mn/Ca, I/Ca, and Fe/Ca), 
foraminiferal assemblages, and stable Mo and N isotopes (Glock 
and Mehrtens, 2021: see Table 2 and Supplementary Table 28). 
Benthic Fluxes and Surface Sediment 
Sampling 
in the Peruvian upwelling area, benthic biogeochemical fieldwork 
focused on the FS Meteor cruises M77/1, M77/2, M92, M136, 
and M137. Off Mauritania, benthic investigations were mainly 
conducted on FS Maria S. Merian cruise MSM17/4 and FS 
Meteor cruise M107 (Sommer et al., 2021; see Table 2 and 
Supplementary Table 29-35). Research questions addressed 
-rontiers in Marine Science | www.frontiersin.ore 
SFB754 Data Legacy 
organic carbon degradation, associated element cycling, and 
solute fluxes in the benthic boundary layer in response to 
variable bottom water redox conditions and hydrodynamic 
forcing (e.g., Bohlen et al., 2011; Noffke et al., 2012; Dale 
et al., 2014, 2016, 2019, 2021; Lomnitz et al., 2016; Sommer 
zt al., 2016; Schroller-Lomnitz et al., 2019; Loginova et al., 
2020; Plass et al., 2020). Effects of variable bottom water 
conditions on seabed nutrient and trace metal release were 
studied during in situ and ex situ sediment incubations and 
‘he analysis of pore water geochemistry. Further emphasis was 
olaced on resolving the imprint of specific microbial processes 
and foraminiferal metabolic activity on element turnover and 
exchange across the sediment water interface (e.g., Glock et al., 
2013, 2019, 2020; Gier et al., 2016, 2017; Scholz et al., 2016, 2017). 
The results were further interpreted using benthic numerical 
models (e.g., Bohlen et al., 2011; Dale et al., 2014, 2015, 
2016, 2017, 2019). The corresponding DOIs are listed in the 
Supplementary Table 29-35. 
In situ Solute Fluxes Measured Using the Benthic 
Flux Lander BIGO 
Benthic solute fluxes of major elements traversing the Peruvian 
OMZ at 11° S and 12° S were determined based on data 
measured {in situ using the two Biogeochemical Observatories 
BIGO I and BIGO II during FS Meteor cruises M77/1-2 (2008, 
11° S; see also Supplementary Table 29), M92 (2013, 12° S; 
see also Supplementary Table 31), M136 (2017, 12° S; see also 
Supplementary Table 34) and M137 (2017, 12° S; see also 
Supplementary Table 35). Solutes fluxes along a zonal transect 
at 18° N off Mauritania were determined during the FS Maria 
S$. Merian cruise MSM17/4 in 2011 (see also Supplementary 
Table 30) and FS Meteor cruise M107 in 2014 (see also 
Supplementary Table 32). The landers are described in detail by 
fannkuche and Linke (2003) and Sommer et al. (2008; 2009; 
2016). Note that during the cruises M77/1-2 the landers were 
named BIGO and BIGO T instead of the usual terminology of 
BIGO I and BIGO II. 
During all cruises the basic functioning principle of the BIGO 
ıype lander was the same. However, for some measurements 
and experiments the lander set-up was modified slightly. 
Details of the modifications are provided in cruise reports 
and specific publications. In brief, the BIGO lander contained 
two circular flux chambers (internal diameter 28.8 cm, area 
651.4 cm?). BIGO T contained only one flux chamber because the 
second one was replaced by the underwater mass spectrometer 
TETHYS, operated by R. Camilli (Woods Hole Oceanographic 
[nstitution). A TV-guided launching system allowed smooth 
emplacement of the observatories at selected sites on the 
sea floor. Several hours after the observatories were placed 
on the sea floor the chambers were slowly driven onto the 
sediment (+30 cm h-7-7)). During this initial time period, the 
water inside the flux chamber was periodically replaced with 
ambient bottom water. After the chamber was fully driven 
into the sediment, the chamber water was again replaced with 
ambient bottom water to flush out solutes that might have 
been released from the sediment during chamber insertion. The 
water volume enclosed by each benthic chamber was variable 
3eptember 2021 | Volume 8 | Article 72330«