Abyssal benthic foraminifera in the Polar Front region (Pacific sector): Faunal composition, standing stock and size structure

Abstract

We have evaluated the quantitative composition of Rose Bengal-stained benthic foraminiferal assemblages of surface samples from two box cores (ANTA98-28 bc; ANTA01-01 bc) collected at the Polar Front in the Pacific sector of the Southern Ocean. Size structure, faunal composition and standing stock were analysed for living (Rose Bengal-stained) and dead foraminifera. The size fractions among 63–150, 150–250 and >250 µm were counted separately in order to study the foraminiferal size distribution and to compare our results with earlier Antarctic studies. The low organic carbon content of the sediment, and hence the limited food availability, is reflected by very low standing stocks and low diversity values. Calcareous taxa dominated dead foraminiferal assemblages that were more diverse than the stained assemblages. In the sediment samples of ANTA01-01 bc, the living fauna contained agglutinated taxa and soft-shelled monothalamous forms. Our data represent the southernmost record of benthic foraminiferal community (63° S) from the Polar Front region in the Pacific sector. These samples provide further evidence for the occurrence of meiofaunal foraminifera in extreme environments, like the Antarctic region, where the uncoupled annual variations in temperature and production cause strong effects on the structure of benthic communities.

Keywords:

• Foraminifera
• Soft-shelled monothalamous foraminifera
• Ecology
• Southern Ocean

Acknowledgements

Many thanks are due to R. Gobbi for the SEM photographs. Special thanks are due to L. Langone for the critical discussion about the article and for the unpublished data of organic carbon. Authors are indebted with A. J. Gooday, S. Korsun and anonymous reviewer for the important suggestions that improving the article. The authors thank the ISMAR-CNR, Bologna for providing the samples. This is contribution no. 1379 from the ISMAR-CNR, Bologna.