Does carbonate ion control planktonic foraminifera shell calcification in upwelling regions?

Shell weights of planktonic foraminifera have been recognized as possible representation of the surface water carbonate CO3 ion concentration and CO2 in the atmosphere. However, to use this power, it is important to understand if the weight of shell CO3 actually reflect water surface. We use the weights of the shells of Globigerina bulloides and Globigerinoides ruber in the size range 300 to 355 m of sediment core recovered from above the lysocline in the upwelling region west of the Arabian Sea. Shell weights G. ruber and G. bulloides show significant correlation with the size of the shell of the recent 16 ka, suggesting that calcification of shell was controlled by the optimum growth conditions. On the other hand, for 16 to 22 ka, there is no correlation between shell weight and shell size. However, the weights of the shells of G. bulloides show a significant negative correlation with annual temperature of the sea surface which suggests that calcification G. bulloides could have been controlled by surface water CO3. Therefore, it is suggested that the weights of shell G. ruber and G. bulloides can not be used to reconstruct CO3 water surface in this region.

Naik S. S., S. Godad P. and P. D. Naidu, 2011. Do you have control of carbonate ions planktonic foraminifera shell calcification in the regions of upwelling? Current Science 101 (10) :1370-1375. Article.