Spatial and temporal effects of anthropogenic carbon on bioerosion

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In the recent discussion how biotic systems may react to raised CO2 and temperatures in the marine realm, we will analyse the role of the most effective endolithic bioeroders - the boring sponges. Several hypotheses predict an increase of sponge-driven bioerosion along with weakening of the calcification potential of their hosts. In an integrated approach we will study interaction effects of global ocean acidification and climate change. Experiments will be conducted on bioeroding sponges as model organisms, because they have unique properties ideal for the planned research allowing simultaneous evaluation of different parameters: Symbiotic bioeroding sponges are likely to be affected by climate change and can be compared to both symbiotic reef builders and asymbiotic bioeroding sponges. Chemical etching of sponges is thought to be enhanced by ocean acidification. By using field sites in two marine environments in different climates (North Sea, tropical Pacific), results will provide a large-scale impression of spatial variation. A field survey at the previously established tropical site will allow a complementary temporal analysis and prognoses (presently for over 10 years). Employing experimental substrates with different solubility properties (aragonite, calcite), we will add another qualitative element. In total, data will convey critical insights into global trends of biologically caused decalcification.