Investigating the effects of past global ocean acidification on marine ecosystems: A novel multiproxy approach

Final Report Summary - PERMIAN-TRIASSIC CAS (Investigating the effects of past global ocean acidification on marine ecosystems: A novel multiproxy approach)

The Permian-Triassic transition was a period of profound environmental change and biologic revolution. The Late Permian witnessed the mother of all the Phanerozoic extinction, which seems to have been triggered by the combined action of several natural processes including global warming, ocean acidification and ocean de-oxygenation. These processes, which have been associated with the rapid additions of volcanic CO2 to the atmosphere, seem to have acted in synergy to promote irreversible changes in the global biogeochemical cycles, which ultimately shaped the evolution of life on Earth.

The global environmental change occurring during the Late Permian – Early Triassic transition and the resulting affection of the marine and continental biota have received major attention from the international scientific community as the rapidity of environmental change during that period may be comparable to that expected for the 21st century. Quantifying the magnitude and rapidity of environmental change during the Late Permian – Early Triassic has thus become a topic of interest as it can provide insights to predict the potential future effects of the rapid release of anthropogenic CO2 to the atmosphere on the global biogeochemical cycles as well as on the future of the earth biodiversity.

To date, several efforts have been made to investigate the limits and magnitude of environmental change during the Late Permian mass extinction. Numerous investigations have been focussed on trying to quantify the real effects of potential kill mechanisms such as ocean acidification and ocean de-oxygenation. Investigations have included the use of traditional proxies of ocean acidification and de-oxygenation such as trace element geochemistry, trace fossil analyses, biomarkers determinations, C-isotope geochemistry, among others. Although the use of these proxies has given light on the potential effects of ocean acidification and de-oxygenation on the marine biologic activity, quantification of the real effects of these two natural processes on the global biogeochemical cycles has remained difficult as most of these proxies only provide information about local marine physicochemical conditions.

In recent years, novel geochemical proxies using variations of isotopes (i.e. Ca, Mo, U and S) have been used to quantifying the extent of environmental change during periods of major marine biologic/evolutionary events. Although several of these proxies have been recently used to relate the Late Permian mass extinction to ocean acidification and de-oxygenation, quantification of the real effects of these natural processes on the marine biologic activity has remained difficult. Major problems arise from the lack of constrains on the global nature of the isotope records used for the quantification of environmental changes across the Permian-Triassic transition and the lack of multi isotope quantitative models that allow better constraining the magnitude and timing of environmental changes related to ocean acidification and de-oxygenation.
The Permian-Triassic CaS project aims to use novel isotope proxies (Ca, S, Mo, U and C isotopes) to better constrain the magnitude and the timing of environmental change during the Late Permian - Early Triassic transition. The project focused on the use of stable Ca and Sr isotope geochemistry (i.e δ44/40Ca and δ88/86Sr) to investigate the effects of rapid additions of volcanic derived CO2 to the atmosphere and the resulting potential ocean acidification on the marine carbonate budget and it relationship to the Late Permian – Early Triassic biologic crisis. The project also aims on using Mo, U and S isotope geochemistry (i.e. δ98/95Mo, δ238/235U, and δ34/32S) to constraint the potential effects of ocean de-oxygenation on the marine biologic activity during this interval. The project has focussed on isotope records of globally distributed carbonate and black shale successions, i.e. China, Turkey, Oman, Italy, Canada, Svalbard, Australia.

The Mo and U isotope work allowed quantifying global changes in redox conditions along the Permian-Traissic transition. Modelling of the Late Permian – Early Triassic ocenaic Mo and U isotope cycles has allowed relating the Late Permian mass extinction to enhanced ocean anoxia and ultimately to ocean euxinia. Deterioration of the marine redox conditions would have occurred within the 200 ky previous to extinction and were likely related to global warming. Ocean anoxia would have continued during the early Triassic and would have caused the delayed recovery of marine biologic activity by at least 500 ky.

Results of the Mo and U isotope work have been submitted to the journal “Proceeding of the National Academy of Sciences of the US”, which recommended integration with additional redox proxies before re-submission in another scientific journal. The Mo and U isotope data were complemented with iron speciation data and S-isotope geochemistry data to further refine the geochemical signals evidencing changing global redox conditions during the Late Permian- Early Triassic transition. The Mo and U isotope geochemistry works were performed at the Stanford University, USA and the University of Hannover, Germany during the outgoing phase of the project. The Iron speciation and S-isotope geochemistry works have been performed at the university of Leeds, U.K. as part of the reintegration training.

The Ca and Sr isotope records have, on the other hand, allowed identifying rapid global changes in the seawater Ca and Sr isotope compositions during the Late Permian – Early Triassic transition. Combination of the Ca and Sr isotope records allowed proposing a long term change on the marine carbonate budget driven by enhanced anoxia and a major short term ocean acidification event coinciding with the Late Permian catastrophe. The acidification effect would have been related to widespread volcanism. Results form the Ca and Sr isotope works are being prepared for submission in international peer review journals.

The IOF research work has allowed quantifying the magnitude and the timing of environmental deterioration associated to rapid additions of atmospheric CO2 to the atmosphere during the Late Permian – Early Triassic transition. Results from this project will be of major relevance to the scientific community, as they will provide insight on the potential future effects of the environmental deterioration resulting from the current rapid releases of anthropogenic CO2 to the atmosphere. Results from this project may thus provide important information for designing mitigation and adaptation policies to climate and environmental change.

It is noteworthy that the severity of environmental change observed during the Late Permian- Early Triassic transition seems to have been similar to that observed during the late Neoproterozoic post-snowball intervals (see Part B of the original IOF proposal). In this project we integrated existing Mo and S isotope data from the Neoproterozoic (post-Marinoan) postglacial interval with U isotope data. Modelling of the multi-isotope record from the post-Marinoan interval has allowed relating major changes in redox conditions to major climate changes. The work on the post-Marinoan interval will be contrasted in future against that from the Late Permian – Early Triassic transition to further constrain the limits of environmental and biogeochemical change occurring during periods of rapid additions of volcanic CO2 to the atmosphere. This will allow testing one of main hypothesis of the original research proposal, which states that ocean de-oxygenation is closely linked to and a potential consequence of global warming.

The ocean biogeochemical cycles and marine biologic activity seems to have been also affected by strong hothouse conditions during the Triassic-Jurassic transition, as well as during several intervals during the Cretaceous. The Fellow, currently assistant professor at the department of Earth and Atmospheric Sciences of the university of Houston, is currently working on new scientific research projects, which main aim is to investigate the effects of rapid additions of volcanic CO2 to the atmosphere and global warming focuses on the marine biologic activity and biogeochemical cycles. These research projects will complement the findings of the IOF research project. The project include the participation of several of the current scientific collaborators of the IOF project i.e. Prof. Paul Wignall and Dr. Rob Newton from the University of Leeds, U.K.; Dr Sylvain Richoz from the University of Graz, Austria; Prof. Anton Eisenhauser from the Geomar Institute, Germany; and Prof. Jon Payne the University of Stanford, USA. This research project, if funded will allow the Fellow to further strengthen his international collaboration network.

Final Report Summary - PERMIAN-TRIASSIC CAS (Investigating the effects of past global ocean acidification on marine ecosystems: A novel multiproxy approach)

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