BURROW ARCHITECTURE AND TURBATIVE ACTIVITY OF THE THALASSINID SHRIMP CALLIANASSA-SUBTERRANEA FROM THE CENTRAL NORTH-SEA

The architecture and development of the burrows of the endobenthic shr imp Callianassa subterranea from the central North Sea were studied in sediment-filled containers and thin cuvettes in the laboratory. Three -dimensional burrows of 81 shrimps were used to describe the 3-dimensi onal burrow architecture. In total, 41 shrimps made 2-dimensional burr ows in cuvettes tailored to their body widths. Development of 8 burrow s over time was registered by regularly mapping burrow outlines and se diment surface levels. Excavation Velocities and sediment expulsion ra tes were derived from changes in the burrow outlines and sediment surf ace levels on the maps. The total tunnel length increased at a rate of 23.4 +/- 6.0 mm h(-1) during the initial stage of burrow development. The length increase levelled off during the completion of the first a nd second U-tubes to 5.6 +/- 1.8 mm h(-1). Initial sediment expulsion rates up to 15.0 cm(3) d(-1) were established. The average sediment ex pulsion rate was 1.080 +/- 0.096 cm(3) d(-1). Extrapolation to a yearl y dry weight (dry wt) sediment turnover, including population density and water temperature effects, resulted in an estimate of 15.5 +/- 2.7 kg dry wt m(-2) yr(-1), equivalent to a 1.2 cm layer. Samples of burr ow lining, expelled sediment and unprocessed sediment did not show cha nges in grain size distributions or organic content due to manipulatio n or processing by C. subterranea. Burrow development experiments carr ied out in enriched seawater systems did not reveal consistent effects of particulate organic matter (POM) on sediment expulsion rates or on the composition of processed or unprocessed sediment.