CHANGES IN FEEDING RATE AFFECT FORAMINIFERAL SPECIES COMPOSITION AND ABUNDANCE (Invited Presentation)

Manipulative culture experiments are one means to assess the impact of a changing environment on foraminiferal species composition and abundance. We performed an 11-month long experiment to assess the impact of different feeding rates on foraminiferal reproduction, growth, and species composition. The experiment was run at 7°C and atmospheric pressure, and included 8 sets of calcein-incubated cultures. In this way, newly precipitated calcite fluoresced, providing a measure of growth and/or reproduction. Material was collected from 3 sites off North and South Carolina (220-, 1400-, 1800-m water depth). Aliquots of the 125-500 micron sediment fraction from the surface ~2 cm were maintained in independent channels of a recirculating seawater system, and fed either twice per week, once per week, twice monthly, or once per month. The diet consisted of 6 species of cultured algae; algae were introduced live to the cultures. Growth occurred in all treatments and reproduction occurred in at least two species: Gavelinopsis cf. translucens and Bulimina aculeata. The 220-m site, known as the Charleston Bump, had the highest diversity of calcifying individuals (e.g., Cibicidoides sp., ?Discorbinella bertholdi, Dentalina sp., and Bulimina aculeata), but the highest calcification yield was in the fed once-per-month treatment from the 1800-m water depth (Gavelinopsis). Results indicate that species respond differently to different feeding regimes, suggesting that environmental change may affect some species more strongly than others. Funded by NSF grant OCE- 1031248 to DCM and JMB.