Globigerinoides sacculifer (Brady)
Globigerinoides sacculifer (Fig. 16) is abundant in tropical water masses. Clear relationships of relative abundance with sea surface temperature and the temperature at 200 m depth exist. The species has narrower tolerances for summer conditions in these parameters, surface water density and the vertical temperature gradient. The species has a preference for water masses with low seasonality in sea surface temperatures and low seasonality in vertical temperature gradients. G. sacculifer shows a maximum in relative abundance in water masses with near average marine salinity but the species has a very broad tolerance and is not a good indicator of salinity. See discussion section in this paper.
Some forms of G. sacculifer develop a distinct sac-like chamber in their terminal stage. They were counted as a separate category. The data in Fig. 16 is combined for sac and non-sac forms. Figure 17 shows correlations of relative abundances
of sac and non-sac forms, and relations with selected physical parameters which do not suggest significant differences in the ecology of both forms, in agreement with culture experiments (Hemleben et al., 1987).
Figure 16: Globigerinoides sacculifer (Brady). Forms with sac chambers included. Plots of relative abundance vs. selected physical parameters and latitude. For preferences in numeric form see appendix.
Figure 17: G. sacculifer with and without sac chamber: correlation of relative abundances, geographic distribution, and relation with water temperature at 200 m. For discussion see text.