The CCD is much deeper in the Atlantic ocean. According to some 1989 data, the maximum depth to find forams in the sediments for the Atlantic is 5.5 km and 5km for the Pacific but the general value is closer to 4 km. These data were obtained by looking if forams were part of the sediments of the ocean floor in different places. Moreover, the CCD is important to consider because some fossil species could be missing in the sediment core. Only the more resistant shells will stay intact.
Forams contain chambers.
Certain species live at different depths in their life so their isotopic composition of the chambers may vary. This shows that it is important to know their mode of life to interpret the data. Also, forams of different sizes might have different isotopic compositions. This might be because the rate of calcification controls the ratio of isotopes. However, coiling direction seems to change with temperature changes.