Unit:
Department of ChemistryLibrary of the School of Science
Dissertation committee:
Δασενάκης Εμμανουηλ, Ομότιμος Καθηγητής, Τμήμα Χημείας, ΕΚΠΑ
Μπακέας Ευάγγελος, Καθηγητής, Τμήμα Χημείας, ΕΚΠΑ
Πούλος Σεραφείμ, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Καραβόλτσος Σωτήριος, Επίκουρος Καθηγητής, Τμήμα Χημείας, ΕΚΠΑ
Καρδιτσά Αικατερίνη, Επίκουρη Καθηγήτρια, Διαχείρισης Λιμένων και Ναυτιλίας, ΕΚΠΑ
Παυλίδου Αλεξάνδρα, Ερευνήτρια Α, Ινστιτούτο Ωκεανογραφίας, ΕΛΚΕΘΕ
Μιχαλόπουλος Παναγιώτης, Ινστιτούτο Ωκεανογραφίας, ΕΛΚΕΘΕ
Original Title:
Biogeochemical processes and fluxes of nutrients and ions at coastal, pelagic and extreme marine environments
Translated title:
Biogeochemical processes and fluxes of nutrients and ions at coastal, pelagic and extreme marine environments
Summary:
This thesis investigates the pore water geochemistry of surficial sediments in diverse marine environments, including the deep sea, a coastal area, and a mud volcano field in the Eastern Mediterranean Sea. By analyzing nutrients, DIC, δ13CDIC and major ions distributions in pore water samples collected from Elefsis Bay, the Olimpi Mud Volcano Field (OMVF) on the crests of the Gelendzhik, Heraklion, Moscow, Leipzig, and Milano mud volcanoes (MVs), located south of Crete on the Mediterranean Ridge, and deep sea sediments south of Crete, distinct patterns of oxic, suboxic, and anoxic conditions in sedimentary settings are revealed. Emphasis is placed on processes that affect nitrogen and phosphorous distribution, sulfate reduction, and anaerobic oxidation of methane, the latter at the OMVF. The spatial variability observed in nutrient and dissolved inorganic carbon pore water concentrations in the deep sea sediments is likely attributed to the S1 sapropel burn down. In Elefsis Bay, significant variability in nutrient concentrations is observed in the part experiencing oxygen deficiency. Ex situ incubation experiments highlight the rapid response of the seafloor to changes in oxygen availability near the bottom water, influencing processes affecting mainly nitrate and phosphate concentrations. Oxygen deficiency at the bottom water leads to very low concentrations of nitrates in the pore waters, resulting in the accumulation of nitrogen, as the denitrification process appears to be significantly impeded. The pore fluid composition reveals significant spatial heterogeneity in surficial sediments in the OMVF, mainly due the supply of ammonium, major ions and methane from the deeper substrata. Geochemical evidence suggests that sulfate reduction and anaerobic oxidation of methane occur in the hypersaline environments of Heraklion and Gelendzhik mud volcanoes. Overall, the pore-fluid composition suggests the OMVF is a dynamic ecosystem, active in terms of fluid and gas expulsion.
The research underscores the complex interplay between biogeochemical processes and environmental factors, providing valuable insights into the response of marine sedimentary systems to changing conditions. These findings contribute to a better understanding of biogeochemical cycling in marine environments.
Main subject category:
Science
Keywords:
Pore water, Diagenesis, Elefsis bay, Deep sea sediments, Mud volcano, Nitrogen, Phosphorous, Sulfate reduction, Anaerobic oxidation of methane
Number of references:
211
File:
File access is restricted until 2025-12-05.
PhD_Rouselaki_final_plus Appendix_ with references as text.pdf
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File access is restricted until 2025-12-05.
