Summary
A series of in situ and aquarium experiments were conducted in the vicinity of the Bailey Peninsula area (Casey Station, East Antarctica) to investigate the bioturbation behaviour of the Antarctic spatangoid urchin Abatus ingens (Koehler 1928). Rates of sediment transport by A. ingens were estimated from measurements of locomotion rates, sediment reworking depth and feeding rates. A. ingens bioturbates and feeds on the surface sediment (top 1 to 2 cm) by pushing diatom communities and sediment ahead and to the side of its track, thus increasing vertical and horizontal sediment transport. Over a 24 h period in situ, A. ingens spends prolonged periods of time stationary (16.7 h) and only short periods of time in locomotion (7.3 h). In the aquarium, however, A. ingens was observed to spend half of the time moving and the other half stationary. Locomotion rate measured in the aquarium was faster (1.95 cm h–1 [1.20 SD]) than in situ (0.30 cm h–1 [0.27 SD]). In addition, A. ingens moves significantly faster during light hours than periods of darkness in situ. An ingestion rate of 0.02 to 0.06 g h–1 of dry sediment was measured for A. ingens, with a gut sediment passage time of 72 to 97 h. A. ingens reworks 2.76 cm3 h–1 (2.52 SD) in situ; however, this calculation (based on forward movement only) may be an underestimate because A. ingens still reworks the sediment (via rocking and rotating on the spot) when it is not moving forwards. It is concluded that A. ingens is a significant contributor to the reworking of sediments in the Antarctic benthic environment.