Linking Aerobic Archaeal and Bacterial Ammonia Oxidation to Anammox in the Benguella Upwelling System.

• Applicant: Professor Dr. Marcel Kuypers
• Subject Area: Atmospheric Science, Oceanography and Climate Research
• Term: from 2006 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 30758459

The Benguella Upwelling System is amongst the most productive waters in the global oceans, resulting in high oxygen consumption in mid-waters and a strong nitrogen deficit. Results from a previous R/V Meteor cruise (No. 57, Leg 3) have demonstrated that anammox instead of heterotrophic denitrification is largely responsible for the large nitrogen loss from these waters (Kuypers et a/., 2005). However, other components of the nitrogen cycle in these waters, particularly in terms of the supply of nitrite to anammox are still poorly understood. Nitrite may come from heterotrophic denitrification, aerobic ammonia oxidation by either bacteria or potentially the recently reported ammonia-oxidizing archaea (Könneke et al., 2005). Crenarchaeota have generally been found abundant in marine water columns (Karner et a/., 2001), and are also present in the Benguella Upwelling System according to preliminary diversity studies (D. Woeken, unpubl. Data). Consequently, we propose to examine quantitatively and qualitatively the contribution of aerobic ammonia-oxidizing archaea versus ammonia-oxidizing bacteria to nitrite in these waters, and to study their potential association or competition with anammox bacteria in the suboxic waters of the Benguella upwelling system. A multidisciplinary approach will be employed. First of all, we will analyze samples collected for 15N-labelling experiments to determine nitrification rates. Secondly, using filter materials already collected on the same RA/ Meteor cruise, we will use a metagenomic approach to identify ammonia-oxidizing crenarchaea, and from the information obtained develop primer sets to quantify them via real-time PCR on both 16S rRNA and functional genes. The abundance of ammonia-oxidizing bacteria, archaea and anammox bacteria will be determined by real-time PCR and FISH, These quantitative microbial data would then be assimilated with nitrification rate measurements and high-resolution nutrient profiles to evaluate the significance of archaeal or bacterial nitrification to the nitrogen cycling in the Benguella upwelling system. It will also promote our understanding on the complex nitrogen cycling processes in the suboxic waters in global oceans.

• DFG Programme: Priority Programmes
• Subproject of: SPP 516: Evaluation of the "Meteor" Expeditions