Efficient recycling of nutrients in modern and past hypersaline environments

Andrea Santulli, Junichiro Kuroda, Takazo Shibuya, Toshihiro Yoshimura, Hodaka Kawahata, Makabe, Stefano Lugli, Naohiko Ohkouchi, Yuta Isaji, Francisco J. Jiménez-Espejo, Vinicio Manzi, Andrea Santulli, Marco Roveri, Nanako O. Ogawa

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

The biogeochemistry of hypersaline environments is strongly influenced by changes in biological processes and physicochemical parameters. Although massive evaporation events have occurred repeatedly throughout Earth history, their biogeochemical cycles and global impact remain poorly understood. Here, we provide the first nitrogen isotopic data for nutrients and chloropigments from modern shallow hypersaline environments (solar salterns, Trapani, Italy) and apply the obtained insights to δ 15 N signatures of the Messinian salinity crisis (MSC) in the late Miocene. Concentrations and δ 15 N of chlorophyll a, bacteriochlorophyll a, nitrate, and ammonium in benthic microbial mats indicate that inhibition of nitrification suppresses denitrification and anammox, resulting in efficient ammonium recycling within the mats and high primary productivity. We also suggest that the release of 15 N-depleted NH 3(gas) with increasing salinity enriches ammonium 15 N in surface brine (≈34.0‰). Such elevated δ 15 N is also recorded in geoporphyrins isolated from sediments of the MSC peak (≈20‰), reflecting ammonium supply sufficient for sustaining phototrophic primary production. We propose that efficient nutrient supply combined with frequent bottom-water anoxia and capping of organic-rich sediments by evaporites of the Mediterranean MSC could have contributed to atmospheric CO 2 reduction during the late Miocene.
Original languageEnglish
Pages (from-to)1-12
Number of pages12
JournalScientific Reports
Volume9
Publication statusPublished - 2019

All Science Journal Classification (ASJC) codes

  • General

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