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Impact of Photochemical and Biological Degradation on Iron Speciation and Biogenic Gases

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cleo
11 diapositives · 255 Views · Sep 22, 2014

This study investigates the impact of photochemical and biological degradation processes on iron speciation and the production of biogenic gases in the Southern Ocean. Focusing on the upwelling of deep water and the upper mesopelagic layer, we explore the effects of solar radiation on dissolved organic matter (DOM) mineralization and trace metal reduction. The research aims to understand the redox complexation of iron, its bioavailability to phytoplankton, and the implications for carbon and nutrient cycles in marine environments.

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  1. KEOPS, OBEX 3 Objective 3: Process Studies The impact of photochemical and biological degradation on iron speciation and the production of biogenic gases Ingrid Obernosterer, LOB Banyls sur Mer

  2. KEOPS, OBEX 3 Why photochemistry experiments ? Solar radiation DOM* + photoproducts DOM Mineralization of organic matter --> C, N, P, S Source or sink of gases --> CO2, CO, OCS, DMS, N2O... Reduction of trace metals or metal complexes --> Fe, Mn, Co

  3. Photochemical processes are of particular interest in The Southern Ocean • KEOPS : • Focus on upwelling of ‘deep water’ -Study of upper mesopelagic water layer (100-300m) - winter mixing

  4. KEOPS, OBEX 3 1) Specific objective of KEOPS: Iron speciation Photochemical Processes Chemistry of iron : redox complexation Bioavailability of Fe to phytoplankton?

  5. Carbon Monoxide (nmol/l) 0 0.5 1 1.5 2 2.5 3 3.5 0 20 40 60 Depth (m) 80 100 (courtesy of C. Law SOIREE) 120 140 160 Photochemical Processes CO2, CO, DMS … 2) Specific objective of KEOPS:biogenic gases

  6. Chemistry of iron : redox complexation Autotrophic Processes KEOPS, OBEX 3 Photochemical Processes Heterotrophic Processes

  7. Biogenic gases KEOPS, OBEX 3 Photochemical Processes Heterotrophic Processes

  8. Photochemical Processes Heterotrophic Processes surface solar radiation (on-deck incubator) -short-term: 1 day-light period biodegradation experiments (in the dark) - short- and long-term: 1 - 7 d ± ± bioassay experiments bioassay experiments KEOPS, OBEX3 Basic Experimental Set-up Seawater, 0.2-µm filtered, will be exposed to

  9. KEOPS, OBEX3 Where will these experiments be performed ? Kerguelen Plateau Upwelling of ‘deep water’ – station C5, ~1000m Bloom-area – station A5 Surface mixed layer < sample < 300m HNLC-area Station D6, ~3000m surface mixed layer < sample < 300m

  10. Let’s discuss: • -Who is interested in participating? • What are your specific questions? • - Define in detail experimental set-up • - Volume of water • UV-transparent incubation bottles/containers (quartz-glass, whirlpack-bags, teflon-bottles, polymethylmetacrylate (PMMA)-bottles) • On-deck incubator • Incubation time and frequency of sub-sampling • Full solar radiation/- UV-B/- UV-A