The project is to investigate whether the increased Fe delivery into the glacial ocean increased diatom production in the Pacific equatorial upwelling regions by conserving silicic acid usage during diatom growth. The project used a range of isotopic proxies d30 Si and d15N and 230Th constrained biogenic fluxes to address this question. We showed that increased diatom production could explain the lower pCO2 levels during glacial periods
This project is to investigate if more efficient use of nutrients, particularly silicic acid used by marine algae to biuld their shells, during the glacial period ied to the uptake of CO2 from the atmosphere into the ocean
The o findings of the project has allowed us to elucidate what was the limiting nutrient in the tropical Pacific ocean and the operation of the biological CO2 pump during the glacial period. The keys finds is that diatom growth under Fe fertilisation during glacial period lead to the conservation of silicic acid. Thus diatoms could grow with out this constraint imposed by silicic acid limitation increasing the rain rate ratio and having an positive impact on the efficiency of the biological CO2 pump in the equatorial Pacific where biological Co2 pump has a large control on atmospheric CO2. Our results showed that silicic acid conserved was transported out of the equatorial pacific region promoting diatom production in the margins. Further, we showed that Nitrate was also not limiting during the glacials in the equatorial Pacific although it isotopic pattern also record the denitrification changes n the margins. The final conclusion is that large parts of the glacial ocean is probablt P limited during the glacials, due to Fe ferlisation and reduced denitrification- a condition quite different from the modern N limited ocean.
|Effective start/end date||1/11/07 → 30/09/12|