Context Our ability to answer to global climate change is currently limited by our misunderstanding of the respective impacts of natural climate variability and of human-induced climate change. This current state of uncertainty partly results from a lack of integration of data from various time scales. This type of integrated information is recorded without interruption in the CALcareous MARine Skeletons. Five Belgian institutions have set up a project aiming to produce a predictive mathematical model using climatic data recorded by calcareous skeletons from three different taxa of marine invertebrates. These taxa selected for their contrasted characteristics (lifetime, growth rate, etc.) are sclerosponges, bivalves, and echinoderms. Project description Objectives The potential as environmental recorders of each of these taxa was demonstrated in our previous project (CALMARS 2001-2005). The originality of the second proposal resides in four new perspectives. A better understanding of biomineralization and pathways of element incorporation in the skeleton that will increase the confidence in the proposed proxies. The study of the new proposed proxies will improve the separation of salinity and temperature signals (dD in the skeleton organic matrix) and offer an insight in the levels of river discharges and the associated weathering processes (dMg in the carbonate). A precise understanding of the barium signal in carbonates will give the keys to describe the estuarine barium cycling, an important aspect for the oceanic Ba proxy. Our multi-specific and multi-proxies model of climatic reconstitution will clarify the reconstitutions carried out to date and, for example, allow a deconvolution of temperature and salinity signals, which commonly act on the same proxy. Methodology CALMARSII approach is based on a combination of field works, laboratory experimentations and mathematical modeling. Field works will implies regular samplings of specimens from selected sites of the North Sea and the Mediterranean Sea. Environmental conditions are continuously monitored at the same locations in order to define the influences of the seasonal variations on the skeleton formation. Specimens are also collected along environmental gradients to define relationships between proxies recording and environmental parameters. Selected proxies are analyzed by high resolution Laser-ablation ICP-MS. For each group, the influence of environmental parameters on skeletal growth rates is investigated in laboratory and on the field. In situ experiments of regeneration are carried out during the same periods. The pathways of proxy incorporation are studied in laboratory after addition of radioactive isotopes. The role of the organic matrix in the processes of biomineralization is also considered. A mathematical model will be deduced after data integration. The analysis of historical specimens from Museum collections will validate this model and lead to paleoclimates reconstitution. Expected results and/or products CALMARSII aims at improving and extending the records of global change in the oceanic domain with a peculiar interest for the climate databases. Through a network of biologists and geochemists of complementary experience, CALMARSII intends to: Improve the comprehension of the mechanisms of calcification and the physiological and biological effects related to incorporation of proxies in the skeleton of sclerosponges, bivalves and echinoderms; Develop a multi-proxy approach permitting to distinguish the signals from temperature and salinity and to reconstruct the evolution of these parameters on the basis of fossil specimens; Understand the specificities of the barium (Ba) proxy to reconstruct Ba inputs from estuaries back through time, contributing to a better interpretation of the oceanic paleoproductivity and paleoalkalinity; Develop a Toolbox software from a multi-species multi-proxy approach. This software will present three applications: (Optimize the empirical relations between the environmental proxies and the parameters; Infer paleoclimates on the basis of proxy data sets; Detect artefacts (e.g. aberrant data, breakdowns, digenesis, etc.) using new mathematical tools. Development of educational aspects from this research is planned. It implies the regular update of the web site set up during the CALMARS project (2001-2005) to describe the principal developments of this second project.