Final Report Summary - BIOCARB (Carbonate Biomineralization in the Marine Environment: Paleo-climate proxies and the origin of vital effects)
The strategy we have pursued is to develop techniques based on a concentration-enrichment of a minor stable isotope of a trace element (e.g. Mg, Sr, or Ca) or a nutrient (e.g. ammonium, nitrate or bicarbonate) that are natural components of seawater, resulting in the formation of biocarbonate or cellular structures with corresponding isotopic enrichments. The biocarbonate or tissue sections are subsequently imaged with secondary and/or transmisions electron microscopy (SEM and TEM, respectively) and then with the NanoSIMS ion microprobe to visualize the locations of the isotopic marker on sub-micrometric length scales, permitting resolution of all ultra-structural details.
We have worked with stable isotopes such as 13C, 15N, 26Mg, 44Ca, and 86Sr. Enhancing the concentration of such isotopes in seawater is likely to inflict a minimum of physiological stress on the organism that could otherwise perturb the biomineralization and metabolic processes we are studying. During the first 30 months of the ERC project, our group has used these stable isotope labeling techniques to obtain information about the dynamics of biocarbonate formation by a number of different organisms, including coral, forminifera, sea-urchin and have made ground breaking progress in the study of coral subcellular metabolism, including assimilation, fixation, remobilization, translocation and utilization of molecules such as ammonium, nitrate and bicarbonate. In the last part of the project we have turned our attention to studying these processes under environmental conditions simulating the effects of global climate change.