Relative changes in planktonic foraminiferal shell weight suggest that different foraminiferal species and size fractions are preserved to different extents. At 2600 m on the Ontong-Java Plateau (OJP), Globigerinoides sacculifer is better preserved than Globigerinoides ruber in the 355--425 ¿m size fraction, whereas small G. ruber specimens are better preserved than their counterparts in the larger size fraction. Downcore variability in shell weight presents a complicated picture of dissolution and controls on shell weight. Shell weight shows only weak covariance with climate indicators at the OJP during the last 425 kyr. In addition, the offset between downcore records at 1600 and 2600 m is smaller than expected from the relationship between shell weight and pressure-corrected carbonate ion concentration obtained from core tops. These observations suggest that the controls on shell weight are more complicated than previously thought and require further study. It also questions the proposed use of shell weight as a reliable proxy of carbonate saturation and carbon dioxide levels.