Dataset Information

The benthic foraminiferal ?34S records flux and timing of paleo methane emissions.

ABSTRACT: In modern environments, pore water geochemistry and modelling simulations allow the study of methane (CH4) sources and sinks at any geographic location. However, reconstructing CH4 dynamics in geological records is challenging. Here, we show that the benthic foraminiferal ?34S can be used to reconstruct the flux (i.e., diffusive vs. advective) and timing of CH4 emissions in fossil records. We measured the ?34S of Cassidulina neoteretis specimens from selected samples collected at Vestnesa Ridge, a methane cold seep site in the Arctic Ocean. Our results show lower benthic foraminiferal ?34S values (?20‰) in the sample characterized by seawater conditions, whereas higher values (?25-27‰) were measured in deeper samples as a consequence of the presence of past sulphate-methane transition zones. The correlation between ?34S and the bulk benthic foraminiferal ?13C supports this interpretation, whereas the foraminiferal ?18O-?34S correlation indicates CH4 advection at the studied site during the Early Holocene and the Younger-Dryas - post-Bølling. This study highlights the potential of the benthic foraminiferal ?34S as a novel tool to reconstruct the flux of CH4 emissions in geological records and to indirectly date fossil seeps.

SUBMITTER: Borrelli C

PROVIDER: S-EPMC6987089 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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The benthic foraminiferal δ34S records flux and timing of paleo methane emissions.

Borrelli C C Gabitov R I RI Liu M-C MC Hertwig A T AT Panieri G G

Scientific reports 20200128 1

In modern environments, pore water geochemistry and modelling simulations allow the study of methane (CH4) sources and sinks at any geographic location. However, reconstructing CH4 dynamics in geological records is challenging. Here, we show that the benthic foraminiferal δ34S can be used to reconstruct the flux (i.e., diffusive vs. advective) and timing of CH4 emissions in fossil records. We measured the δ34S of Cassidulina neoteretis speci ...[more]

PMID: 31992778

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Project description:Chienhsun Chen and Hui-Ling Lin (2017) Coral reefs in the South China Sea are threatened by environmental changes and anthropogenic disruptions. Foraminifera, a group of unicellular shelled protists, has been considered a reliable indicator of water quality and reef health. However, this indicator has not yet been used to study coral reefs in the South China Sea. In this study of foraminifera in the lagoon of Dongsha Atoll, both the assemblage diversity and the functional group composition were investigated. The FORAM index (FI), a numerical indicator based on functional group composition, was used to evaluate the condition of the coral reef of the Atoll lagoon. A typical assumption is that FI = 4 is the minimum index value corresponding to a suitable environment for the growth of calcifying organisms. Environments with FI values between 2 and 4 are unsuitable to marginal for recovery of coral communities after a mortality event. Data were recorded regarding a total of 287 foraminiferal species. Approximately 68% of the tests belonged to the porcelaneous taxa; the Quinqueloculina, Triloculina, and Pseudomassilina species were well represented. Hyaline foraminifera were less abundant than porcelaneous foraminifera; the agglutinated foraminifera were the least abundant. Multivariate analyses revealed four clustering groups. The functional groups were classified according to FI's definition; the heterotrophic group was the most abundant, accounting for 82% of foraminiferal abundance. The symbiont-bearing group was the second most abundant, with a relative abundance of 12%; and the stress-tolerant group was the least abundant. Two samples had FI values slightly higher than 4; Amphisorus and Calcarina were dominant, but the other symbiont-bearing foraminifera had lower values. These high FI values can be associated with seagrass meadows or relict shells in an altered environment. Eighty percent of the sediment samples had FI values lower than 4, indicating that most of the benthic habitats in the Dongsha lagoon are not suitable for coral growth and reef recovery. The present findings provide an alternative evaluation method based on foraminiferal assemblages for future studies on the environmental changes of coral reefs.

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The benthic foraminiferal ?34S records flux and timing of paleo methane emissions.

Publications

The benthic foraminiferal δ<sup>34</sup>S records flux and timing of paleo methane emissions.

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