Estimation of calcification rate of Spirillina vivipara

Calcareous foraminifera is a unicellular protist that possesses calcium carbonate shells and is commonly found in the oceans. Biomineralization of these organisms has been extensively studied, as the shells of these organisms hold valuable information about past environmental conditions. In particular, the evolution of foraminiferal assemblages in different environments has been well-documented throughout geologic time, and they are often used as facies fossils and reference fossils.In this study, we aimed to estimate the calcification rate of the species Spirillina vivipara, which is known for its fast generational turnover and rapid shell growth rate. Foraminifera samples were collected from the Enoshima Aquarium in Fujisawa City, Japan, and kept in an incubator with a 12-hour light/dark cycle and a constant temperature of 20°C. The foraminifera was reared in filtered seawater with a salinity of 35 and fed twice a week with live Dunaliella sp.To observe the calcification process, we recorded the elongation rate of testes by time-lapse observation using differential interference microscopy and calcein-containing seawater to mark the shells. We then used multiple techniques, including a focused ion beam (FIB)-SEM, to measure the thickness of the shells. In this presentation, we will present the results of our study on the shell growth rate of foraminifera and compare them with previous studies.