Objectives

R/V Olaya Cruise MPI / IMARPE

Objectives

Royal NIOZ will participate in a cruise with the Peruvian research vessel Olaya at the west coast of South America. The cruise is led by the Max Planck Institute for Marine Microbiology in Bremen, Germany. Main tasks: Nutrient cycling and the molecular ecology, metagenomics and organic geochemistry in relation to Anmmox bacteria in the water column. Non-steady state climate variation reflected in the porewater chemistry, sulphate reduction rates, organic geochemistry and stabile nitrogen isotopes in gravity cores and multicorer samples. Large nitrate storing sulphur bacteria along with metagenomics, DNA expression, and biogeochemical processes at the sediment-water interface. Phosphorite formation in association with sulphur bacterium Objectives The Peruvian Upwelling System is characterized by a strong oxygen minimum zone, in which anaerobic ammonium oxidising (anammox) bacteria may play an important role in the nitrogen cycle. Jane Rattray, a PhD student at the Department of Marine Biogeochemistry and Toxicology (NIOZ-MBT), will investigate the abundance of anammox bacteria in the water column, using their characteristic ladderane lipids as a tracer. Anammox bacteria derive their energy from the anaerobic combination of the substrates ammonia (NH₄+) and nitrite (NO₂-) into dinitrogen gas (N₂) according to equation 1. NH₄+ + NO₂- → N₂ + 2H₂O (1) This reaction takes place in a separate cell compartment in the cytoplasm, called the anammoxosome. This cellular organelle is surrounded by a unique set of membrane lipids containing a number of cyclo-butane rings. Because the molecular structure of these molecules resembles a ladder, they are called ladderane lipids (Sinninghe Damsté et al., 2002). These lipids give rise to an exceptionally densely-packed membrane, forming a tight barrier against diffusion which is required to maintain concentration gradients with the remainder of the cell and to protect it from the toxic anammox intermediates (e.g. hydrazine). Using the ladderane lipids as unique tracer lipids, it was recently shown that anammox also occurs in the marine environment (Kuypers et al., 2003). Anammox may represent a quantitative important process for the loss of nitrogen from anaerobic systems in the ocean: anammox results in the conversion of nutrient N into dinitrogen gas, which is for most marine organisms an inaccessible form of nitrogen. References: Sinninghe Damsté J. S., Strous M., Rijpstra W. I. C., Hopmans E. C., Geenevasen J. A. J., van Duin A. C. T., van Niftrik L. A., and Jetten M. S. M. (2002) Linearly concatenated cyclobutane (ladderane) lipids from a dense bacterial membrane; Nature 419, 708-712. Kuypers, M.M-M, Sliekers, A.O., Lavik G., Schmid, M. Jørgensen, B.B, Kuenen, J.G., Sinninghe Damsté, J.S. Strous, M., Jetten, M.S.M., (2003) Anaerobic ammonium oxidation by Anammox bacteria in the Black Sea; Nature 422, 608-611. _______________