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Study of N and C dynamics in aquatic ecosystems

Study of N and C dynamics in aquatic ecosystems. Dr Natacha Brion, Dr Marc Elskens, Dr Steven Bouillon, Dr Frank Dehairs, DrS Emilie Chevalier, DrS Sandra De Galan, DrS Perrine Mangion, Dr Willy Baeyens. Why ?. Living organisms = C, N, H, O, P + trace elements

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Study of N and C dynamics in aquatic ecosystems

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  1. Study of N and C dynamics in aquatic ecosystems Dr Natacha Brion, Dr Marc Elskens, Dr Steven Bouillon, Dr Frank Dehairs, DrS Emilie Chevalier, DrS Sandra De Galan, DrS Perrine Mangion, Dr Willy Baeyens

  2. Why ? • Living organisms = C, N, H, O, P + trace elements • Life or dead of all organisms depends on the availability and usefulness of C and N holding material. • Eg: plant: CO2 and NH4 or NO3 and PO4 • Eg: animal: proteins, sugars, lipids

  3. N and C cycles Subdivised by molecule, size, biodegradability, origin etc… DON Detritus NH4 PN autrotrophe Species Size Etc.. Living NO3 N2 Heterotrophe DOC DIC POC INCREASING COMPLEXITY

  4. Methodological tool I: Study the natural variations of 13C and 15N in various C and N pools • Considered pools: • Dissolved inorganic (DIN-DIC) • Dissolved organic (DOC-DON) • Particulate organic (SPOM, living organisms) • Particulate inorganic (carbonates) • Allows to highlight: • Origin of material • Major transformation pathways • Foodweb chain pathways (who eats who) • Type of information: • qualitative • quantitative when combined with a modelling approach

  5. Methodological tool II: Perform incubation experiments with enriched 15N or 13C tracers • Tracers : dissolved inorganic or organic N and C • Incubation: one tracer is added per incubation bottle or a combination of one N and one C tracer in one bottle • After incubation: measure the 15N and/or 13C in different N and C pools • DIN – DIC pools • DON – DOC pools • PON – POC pools

  6. Use an isotopic mass balance model to compute transformation rates • Type of transformation rates that can be measured: DON DOC NH4 PN DIC POC NO3 N2

  7. Study of N and C cycle in Northern Tanganyika Lake

  8. Relative role of macrophytes, phytoplankton and sediments in the uptake and release of inorganic nitrogen in a small river N-NH4 kg N / day 3-40 0.1-0.2 23-230 15-180 0-2

  9. N cycling in the Southern Bight of the North Sea Nitrate + Nitrite µM

  10. N cycling in the Scheldt estuary

  11. N dynamics in the Zenne river in Brussels TN/day

  12. The fate of mangrove carbon and nitrogen in different mangrove ecosystems Studied by looking at natural variations of 15N and 13C in different compartments of the ecosystem

  13. And… • N and C cyling oin Southern Ocean • N and C cycling in Pacific Ocean • N and C cycling in Atlantic Ocean • …. And many others

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