As part of our ongoing evaluation of the shell weight proxy, measurements were carried out on plankton species from South Atlantic cores. The results portray a complex picture. Whereas ideally these weights should be influenced only by surface water carbonate ion concentration (growth weight) and deep water pressure-normalized carbonate ion concentration (extent of weight loss due to dissolution), it appears that other environmental factors may influence growth weight and that variable pore water - bottom water offsets may complicate the extent of dissolution.