Effects of calcein incorporation on benthic foraminiferal community under various concentrations and incubation durations

Abstract

Calcein is widely used to mark the new calcium carbonate structures in foraminifera, but it remains unclear whether calcein has effects on the biological features (i.e., abundance, size). Here the biological effects of calcein on benthic foraminifera were investigated using a two-factor crossed experiment in which foraminiferal communities (10,393 live specimens in total) were cultured in seawater spiked with calcein at four concentrations (control, 1, 5, and 10 mg/L) and for three incubation durations (2, 4, and 6 weeks). Each treatment was performed in triplicate, yielding 36 samples (4 concentrations × 3 durations × 3 replicates). Results showed that high calcein concentrations (10 mg/L) and long incubation times (6 weeks) significantly affected the abundance, and the Margalef and Shannon-Wiener diversity indices, of foraminiferal communities. Dominant species showed a species-specific response to calcein. Interestingly, different foraminiferal test types showed different responses to calcein: the proportion of miliolids significantly increased in all calcein treatments (1, 5, and 10 mg/L) relative to the control (without calcein), in contrast to the proportion of rotaliids. Thus, calcein might have a positive effect on foraminiferal communities by enhancing porcelaneous groups. Given that high calcein concentrations and long incubation times can have negative effects on foraminifera, we suggest a relatively safe manipulation: at the beginning of a culture experiment, calcein (≈5 mg/L) is added as an initial marker, then replaced with natural seawater halfway through the experiment. About 4 weeks before the end of the incubation, calcein can again be added to cultures. • 11,581 foraminiferal specimens were selected and identified as well as 10,393 living specimens analyzed. • The biological effects of calcein on benthic foraminifera were first evaluated comprehensively and analyzed quantitively. • The diverse response to calcein in different foraminiferal shells was revealed. • A relatively safe culture manipulation for foraminifera with calcein was recommended.