Summary

EXECUTIVE PUBLISHABLE SUMMARY,
RELATED TO THE OVERALL PROJECT DURATION

Contract n� No: EVK2-CT1999-00031 Project Duration: 2000 - 2003

Title: IRONAGES

Objectives: The overall objective of the IRONAGES project is to develop new realistic OBCM's for budgeting and exchanges of both CO2 and DMS, by implementing (i) co-limitation by 4 nutrients of 5 major taxonomic classes of phytoplankton, (ii) DMS(P) pathways, (iii) global oceanic iron cycling, (iv) different chemical forms of iron and (v) supply of iron from below and above into surface waters. The new OBCM's will predict realistic climate scenario's, notably climatic feedbacks on oceanic biogeochemistry.

Scientific achievements: Iron input into the oceans, iron originating from reduced Fe(II) from anoxic sediments of coastal margins (iron from below), as well as from aeolian input from above of Fe(II) dissolved in rainwater from Sahara-derived dust blown over the central Atlantic (iron from above) was quantified. These fluxes were related to observed phytoplankton production, CO2 gas exchange and DMS emission. Moreover , the different chemical species of Fe were determined. Finally, these field data were used to construct a simple global Fe cycling model.
The physiology, life cycle, Fe limitation, export production, CO2 uptake and DMS emissions for the two major DMS producing colony-forming Phaeocystis sp. and calcifying Emiliania huxleyi as well as three other major classes of marine phytoplankton (diatoms, N2-fixing diazotrophs and the small pico- and nanoplankton) was synthesised from existing literature in combination with additional laboratory experiments. The ensuing know-how was fed into below ecosystem modelling, as well as into the DMS(P) pathway modelling.
The existing phytoplankton ecosystem model (SWAMCO) was expanded with the 3 other taxonomic groups and also the DMS(P) pathways simulation .
Expansion of the global iron model as well as the SWAMCO model were used for improvement of the Ocean Biogeochemical Climate Model (OBCM's), with as ultimate aim of IRONAGES to run climate change scenario's, notably changes in Fe inputs, with special attention to climatic feedbacks (warming) on the oceanic cycles and fluxes.

Simplified cartoon of a marine ecosystem incorporating multiple phytoplankton species, CO2, DMS, and Fe from above and from below

Main deliverables: Field data on iron fluxes from sediments as well as from atmospheric input, collected during several cruises, were made available. An Fe certification excercise ensured reliable measurements of ultra-low iron concentrations. A global Fe cycling model was constructed. Reviews of 5 major taxonmic groups of marine phytoplankton were made available. Additional aboratory experiments filled lacks in physiological knowledge on these groups. An ecosysme model. SWAMCO, was expanded using the scientif knowledge on the 5 taxonomical groups. The simple Fe cycling model, as well as the SWAMCO model, were used to improve Ocean Biogeochemical Climate Modelling.

Socio-economic relevance and policy implications: The results from IRONAGES helps to address the issues of quality of life and health and safety by constructing tools with which, future climate forecasts will have a greater degree of certainty than is currently available. The results of this work directly enables EU policymakers and planners to propose new policies that deal with the impacts of climate change with the highest possible confidence. The development of the marine ecosystem models, creates a tool to test the sustainability of such systems under conditions of climate change or anthropogenic perturbation. This allows then for ecosystem conservation and management resource policies to be developed with reduced uncertainty about the possible changes in climate and the ramifications arising from that.
Any policy decision on reduced CO2 emissions will implicitly affect the longer-term availability of natural resources: petroleum, natural gas and coal.

Conclusions: The improved OBCMs developed within IRONAGES enable studying the influence of potential climate change on the biogeochemistry in the oceans and possible feedbacks to climate. Changes in mixed layer depth and temperature driven by climate change will influence the composition of phytoplankton, leading to changes in the biogeochemical cycling of a number of compounds, such as dimethylsulfide that influence climate. Changes in DMS production have the potential to offset climate changes due to increasing CO2 levels, especially singe anthropogenic sulfur emissions to the atmosphere have been reduced strongly in recent time.

Dissemination of results: The main products of the IRONAGES project are publications in international, peer reviewed journal, oral and poster presentation at (inter)national conferences and/or seminars, a website (http://kellia.nioz.nl/projects/) and theses.

Keywords: Ocean Biogeochemical Climate Model, climate change, marine phytoplankton, iron limitation, iron certification. Iron specaition, carbon dioxide, DMS, Phaeocystis sp., Emiliania huxleyi, diatoms, Trichodesmium, picophytoplankton, modelling, ecosystem.