Living (stained) deep-sea foraminifera from the Sea of Marmara: A preliminary study

Abstract

In this preliminary study, we investigate living (stained) foraminifera from the Sea of Marmara. We focus on the faunal composition and geochemical signatures (trace elements, carbon and oxygen stable isotopes) in foraminiferal tests at two deep-sea sites (329 and~1240 m depth respectively). Documented by ROV observations and sampling, both study areas are heterogeneous (including bacterial mats and carbonate concretions), proximal to cold seeps and consist of dysoxic bottom water (O 2 < 20 µmol/L). The prevailing dysoxia at both study areas restricts foraminiferal diversity to very low values (S < 9, H' < 0.97). Stress-tolerant species Bolivina vadescens and Globobulimina affinis dominate living faunas at both sites. The highest foraminiferal standing stock is recorded at the shallowest site underneath a spreading bacterial mat. No benthic foraminifera from either site possess geochemical signatures of methane seepage. Our biogeochemical results show that use of foraminiferal Mn/Ca ratios as a proxy for bottom water oxygenation depends strongly on regional physiography, sedimentary processes and water column structure.

Fluids and processes at the seismically active fault zone in the Sea of Marmara

“…It has been shown that the gas bubbles emitted at the seafloor are mixtures of primary and secondary microbial gases with thermogenic and mantlederived gases with very asymmetric contribution of each source (Ruffine et al, 2018a). The sediments in the vicinity of the seeps host living benthic Foraminifera, and a study from samples collected on the Central High and the Çınarcık Basin show that Bolivina vadescens and Globobulimina affinis are the two dominant species at the study areas (Fontanier et al, 2018). Three articles (Akhoudas et al, 2018;Çağatay et al, 2018;Teichert et al, 2018) deal specifically with the texture, mineralogical and isotopic compositions and genesis of authigenic carbonate crusts associated with cold seeps in the SoM.…”

Interpretation of Late‐Pleistocene/Holocene Transition in the Sea of Marmara From Geochemistry of Bulk Carbonates

“…Relationship between Mg/Ca and Sr/Ca (mol ratio) in seafloor authigenic carbonate crusts (Çağatay et al, ), benthic foraminifera (Fontanier et al, ), and bulk carbonate in sediments from the Marmara Sea (this study). The dashed lines correspond to mixing lines between hypothetical end‐members: terrigenous material, aragonite, Mg‐calcite, and biogenic calcite.…”

“…The contribution of biogenic, authigenic, and detrital carbonates to bulk carbonates were investigated with a mixing model in which four end member ratios of Sr/Ca and Mg/Ca were used (Bayon et al, ; Çağatay et al, ; Fontanier et al, ; Figure ). The results from MRS‐CS‐16 follow a mixing line between detrital calcite and biogenic calcite.…”

“…The X and Y ordinates are Mg/Ca (mol/mol) and Sr/Ca × 10 3 (mol/mol), respectively. The values of aragonite and Mg‐calcite are cited from seafloor carbonates in the SoM (Çağatay et al, ), and the values for biogenic calcites are cited from foraminifera in the SoM (Fontanier et al, ). Each member is connected under exponential coordinates.…”

Mg∕Ca, Sr∕Ca and stable isotopes from the planktonic foraminifera &lt;i&gt;T. sacculifer&lt;/i&gt;: testing a multi-proxy approach for inferring paleotemperature and paleosalinity

“…Mg concentrations were calculated using masses 24 and 26; Sr concentrations were calculated with mass 88. One big advantage in using LA-ICP-MS measurements is that single laser pulses remove only a few nanometers of material, which allows high-resolution trace element profiles to be acquired (e.g., Reichart et al, 2003;Regenberg et al, 2006;Dueñas-Bohórquez et al, 2009Hathorne et al, 2009;Munsel et al, 2010;Dissard et al, , 2010aEvans et al, 2013Evans et al, , 2015Steinhardt, 2014Steinhardt, , 2015Fehrenbacher et al, 2015;Langer et al, 2016;Koho et al, 2015Koho et al, , 2017Fontanier et al, 2018;de Nooijer et al, 2007de Nooijer et al, , 2014de Nooijer et al, , 2017aJentzen et al, 2018;Schmitt et al, 2019;Levi et al, 2019). Element concentrations were calculated for the individual ablation profiles integrating the different isotopes (glitter software).…”