Estimation of the growth pattern of Baculogypsina sphaerulata (Foraminifera) in a tropical environment using a floating chamber method

Calcium carbonate shells produced by large benthic foraminifers (LBF) are major components in sediments on coral reef islands. Quantifying growth patterns of LBFs is important for accurate estimation of calcium carbonate production. To quantify the growth pattern of Baculogypsina sphaerulata in a tropical area, we developed a novel rearing method with high survival rate (> 90%) by creating constant disturbance with the combination of a floating chamber and coral sand. Through the rearing experiments, coral sand has a significant inhibitory effect on lethal epiphyte infestation on B. sphaerulata in a rearing chamber. This implies that the inhibitory effect by such disturbance on the epiphyte may be one of the reason that B. sphaerulata prefer the most exposed areas among LBFs. The novel rearing method allowed the quantification of the relationship between size and growth rate. The growth rate of B. sphaerulata showed size dependence with a peak at 0.8-1.2 mm2, and development time to adult size was estimated at 1.3 year with substantial variation induced by variability in growth parameters. The estimated development time is similar to that reported in subtropical areas (1.5 year). This quantified growth pattern of the species will apply to the analysis of population dynamics and estimation of CaCO3 productions of the species in a tropical area.