Bathymetric and regional benthic foraminiferal distribution on the Espírito Santo Basin slope, Brazil (SW Atlantic)

Almeida, Fabiana K. de; Mello, Renata Moura de; Rodrigues, Alex de Freitas; Bastos, Alex Cardoso

doi:10.1016/j.dsr.2022.103688

Cited by 9 publications

(5 citation statements)

References 94 publications

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“…Studies have demonstrated that high surface concentrations of chlo a are associated with increased primary productivity and organic carbon export; this situation stimulates the trophic web and, generally, provides higher supply of organic matter to the bottom (Altenbach and Struck, 2001;Ducklow et al, 2001;Vicente et al, 2021). Our data show a relationship between the input of phytodetritus and the increase in the number of two species (E. exigua and G. subglobosa), considered opportunistic species (r-strategists) (Gooday, 1988(Gooday, , 1993, corroborating the observations of Duchemin et al (2007) and Almeida et al (2022). It was also observed that species richness is positively correlated with phytopigments, which may indicate a preference for phytoplanktonic food (also protein-rich).…”

Section: Discussionsupporting

confidence: 89%

Deep-sea living (stained) benthic foraminifera from the continental slope and São Paulo Plateau, Santos Basin (SW Atlantic): ecological insights

Araújo,

Yamashita,

Santarosa

et al. 2023

Ocean Coast. Res.

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This study aimed to characterize the spatial distribution and composition of living Benthic Foraminifera (BF) and to comprehend how environmental conditions (e.g., organic matter) can affect communities of these protozoa in the northern and southern sectors of the Santos Basin (SB), in the continental slope and São Paulo Plateau. In this context, 23 stations (65 samples including replicates at each station) were collected between 400 and 2,400 m water depth. Multivariate analyses revealed that the ecological structure of the community changes mainly along the bathymetric gradients. Stations located between 400 and 700 m, both in northern and southern sectors, are characterized by the presence of indicator species of high intensity of currents, such as Globocassidulina subglobosa and Trifarina bradyi. These stations are also mainly marked by the occurrence of Epistominella exigua, a phytodetritivore species. The stations at 1,000 and 1,300 m depth, in both sectors, are characterized by high accumulation of organic matter in the sediments, which favors the development of agglutinated foraminifera species, such as those of the genus Reophax. Finally, the lower slope and the São Paulo Plateau, in both sectors, are oligotrophic regions, with pulses of labile organic carbon, probably low current velocities and the presence of Alabaminella weddellensis. The quantity and quality of food, which are closely related to hydro-sedimentary dynamics and bentho-pelagic coupling in the slope and São Paulo Plateau, are the main factors that influence the distribution of living BF assemblages in the SB.

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Section: Discussionsupporting

confidence: 89%

Deep-sea living (stained) benthic foraminifera from the continental slope and São Paulo Plateau, Santos Basin (SW Atlantic): ecological insights

Araújo,

Yamashita,

Santarosa

et al. 2023

Ocean Coast. Res.

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“…The here evidenced increase in the export of organic matter (OM) to the seafloor from MIS 5 to MIS 4 (and to a lesser extent in MIS 3) aligns with the findings of Rodrigues et al (2018). They observe a decrease in the infaunal/epifaunal benthic foraminifera ratio in core SIS-249, indicating a shift in the bioavailability of OM from refractory to labile forms (Gooday, 1993;Smart et al, 1994;Gooday, 2003;Garcia-Chapori et al, 2014;de Almeida et al, 2022). This change has significant implications for calcium carbonate preservation.…”

Section: Organic Matter Export and Seafloor Dynamicssupporting

confidence: 82%

Surface fertilisation and organic matter delivery enhanced carbonate dissolution in the western South Atlantic

Suárez-Ibarra,

Freire,

Frozza

et al. 2023

Front. Ecol. Evol.

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The last glacial inception was characterised by rapid changes in temperature, atmospheric pCO2, and changes in the water mass geometry of the major ocean basins. Although several climatic feedback mechanisms have been proposed to explain the glacial/interglacial cycles witnessed in the Quaternary, the exact mechanistic responses of these processes are still under constrained. In this study we use proxies including planktonic foraminifera compositional assemblages and oxygen stable isotopes to reconstruct past changes in sea surface productivity, stratification, and carbonate dissolution. We use core SIS-249 (2,091 mbsl, western South Atlantic 30°S 47°W), spanning 30–110 thousand years ago (ka), and currently bathed by modern Northern Component Water. We test existing hypotheses suggesting that the orbital obliquity cycle modulates the biological pump in the study area. Spectral analysis run on our synthesised productivity proxies recognises a ~43 kyr-cycle, related to the obliquity cycle. We propose that the enhanced productivity is produced by two mechanisms: i) the glacial upwelling of subsurface nutrient-rich waters and, ii) the continental (wind-driven dust and riverine outflows) fertilisation of the photic zone, with the latter process being obliquity-paced. We also suggest that not only the increased organic matter export but also a change in its bioavailability (from refractory to labile) led to calcium carbonate dissolution, as the degradation of the more soluble organic matter decreased the pH of the glacial bottom water, partially dissolving the calcium carbonate. Although our correlation analyses show a strong benthic-pelagic coupling through the relation between the enhanced biological pump and carbonate dissolution (ρ<0.05, r=0.80), we cannot reject the potential of corrosive Southern Component Water bathing the site during the glacial. Finally, we highlight that these processes are not mutually exclusive and that both can be modulated by the obliquity cycle.

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“…As long as data for benthic and planktonic communities, as in our case, were extracted from the same sieve size fraction. The resulting B:P ratios will be comparable, indeed, being used in the literature (e.g., de Almeida et al, 2022). The ostracod valves abundances (number of valves in the >150 µm fraction per gram of sediment), and the δ 13 C record of Uvigerina spp.…”

Section: Oceanographic Settingsupporting

confidence: 54%

Calcium Carbonate Dissolution Triggered by High Productivity During the Last Glacial–Interglacial Interval in the Deep Western South Atlantic

et al. 2022

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Studies reconstructing surface paleoproductivity and benthic environmental conditions allow us to measure the effectiveness of the biological pump, an important mechanism in the global climate system. In order to assess surface productivity changes and their effect on the seafloor, we studied the sediment core SAT-048A, spanning 43–5 ka, recovered from the continental slope (1,542 m water depth) of the southernmost Brazilian continental margin, deep western South Atlantic. We assessed the sea surface productivity, the organic matter flux to the seafloor, and calcite dissolution effects, based on micropaleontological (benthic and planktonic foraminifers, ostracods), geochemical (benthic δ13C isotopes), and sedimentological data (carbonate and bulk sand content). Superimposed on the induced changes related to the last glacial–interglacial transition, the reconstruction indicates a significant and positive correlation between the paleoproductivity proxies and the summer insolation. From the reconstructed data, it was possible to identify high (low) surface productivity, high (low) organic matter flux to the seafloor, and high (low) dissolution rates of planktonic Foraminifera tests during the glacial (postglacial). Furthermore, within the glacial, enhanced productivity was associated with higher insolation values, explained by increased northeasterly summer winds that promoted meandering and upwelling of the nutrient-rich South Atlantic Central Water. Statistical analyses support the idea that productivity is the main cause for seafloor calcium carbonate dissolution, as opposed to changes in the Atlantic Meridional Overturning Circulation (at least for the 25–4 ka period). Further efforts must be invested in the comprehension and quantification of the total organic matter and biogenic carbonate burial during time intervals with an enhanced biological pump, aiming to better understand their individual roles.

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Bathymetric and regional benthic foraminiferal distribution on the Espírito Santo Basin slope, Brazil (SW Atlantic)

Cited by 9 publications

References 94 publications

Deep-sea living (stained) benthic foraminifera from the continental slope and São Paulo Plateau, Santos Basin (SW Atlantic): ecological insights

Deep-sea living (stained) benthic foraminifera from the continental slope and São Paulo Plateau, Santos Basin (SW Atlantic): ecological insights

Surface fertilisation and organic matter delivery enhanced carbonate dissolution in the western South Atlantic

Calcium Carbonate Dissolution Triggered by High Productivity During the Last Glacial–Interglacial Interval in the Deep Western South Atlantic

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