Project

project details

The chemical or isotopic composition of calcareous skeletons have long been recognized as records of past and present environmental conditions and thus allow reconstruction of the environmental history. Recent efforts have given a high priority in coral research to produce indicators of specific aspects of climate that can be integrated with other high resolution paleoclimate data derived from tree rings, ice cores or sediments. Each type of archive provides a valuable record, with unique strengths but weaknesses. Because the composition of biogenic carbonates is also clearly influenced by biological factors, the correct interpretation of these chemical archives requires a precise understanding of the processes controlling the incorporation of elements. Furthermore, to make the reconstruction of past environmental conditions as reliable as possible at a global scale implies that recorders from the widest taxonomic, geographical, and ecological ranges are used. Currently, such a large range is not available for the oceanic compartment. Accordingly, the objective of the CALMARS research network is to extend series of environmental data from oceanic origin by using the skeleton of marine invertebrates belonging to different phyla, occurring from temperate regions to the tropics. Potential recorders have been selected among three taxa, viz. sclerosponges, bivalves, and echinoderms, for their contrasted characteristics: lifetime, growth rate, and mineralization features. Areas of interest will spread from the North Atlantic Ocean to the Caribbean. The potential as environmental recorders of each of these taxa is well known, and the originality of the present proposal rather resides in three new perspectives. First, the comparative analysis of contrasted taxa will sustain the validity of the recorded global changes. Second, laser ablation technology will ensure day to seasonal resolution depending of the taxon used. Three, focus will go to a better understanding of the pathways of proxy incorporation and on the relative controls by environmental and physiological conditions, emphasizing on reconstruction of sea surface temperature (SST), salinity, phytoplankton biomass and productivity, and trace metal content. Our approach is based on a combination of field and laboratory work. Field experiments will consist in long term (>1 year) monitoring of environmental conditions at selected sites in tropical and temperate settings (North Sea & Scheldt estuary, Belgium; Norway; North Carolina, USA; Jamaica). Proxies studied will be Mg, Sr, Ba, Cd, Mn, U, B, Pb, Zn and d13Ccarb, d18Ocarb. Specimens of each group will be sampled along environmental gradients in order to analyze relationships between proxies found in the skeleton and in the environment. Effects of environmental parameters will be tested for each group under experimental conditions (in situ with incubation chambers or in aquarium). Impact of ambient substrate concentrations and physicochemical conditions will also be studied in controlled in-vitro and semi in-vitro experiments, during which incorporation of proxy will be followed after radioactive and stable isotope spiking. to ascertain results obtained along naturally occurring gradients. In addition, specimens preserved in museums will help to extend data in time and localities. From observed relationships between patterns of recorded proxies and environmental parameters, corrected for possible physiological effects, transfer functions will be developed. These may then be applied to proxy records predating the era of observational climate analysis. The output of the this study offers the possibility to assess and constrain climate model performances.