SEDIMENT BIOTURBATION BY POLYCHAETE FEEDING MAY PROMOTE SEDIMENT STABILITY

PALOMO, M.G.; IRIBARNE, O.

BULLETIN OF MARINE SCIENCE

ROSENSTIEL SCH MAR ATMOS SCI

Año: 2000 vol. 67 p. 249 - 257

0007-4977

Feeding characteristics and burrowing activities of bioturbators can change the dynamicof soft bottoms. The nereidid polychaete Laeonereis acuta (Treadwell, 1923), is animportant component in the intertidal mudflats of the Mar Chiquita coastal lagoon(37°32'S, 57°19'W; Argentina). Its feeding mode and burrowing activity were examinedin relation between sediment bioturbation and sediment bedload transport. L. acuta is adeposit feeder that lives in burrows connected to the surface. Burrow depth is related tosize, although most worms inhabit the upper 5 cm. Burrows less than 21 mm total lengthwere U-shaped whereas individuals >21 mm in length were found in straight verticaltubes with only one aperture at sediment-water interface. The number of sediment moundsproduced by L. acuta feeding were correlated with their density (1324.16 ind m−2), producingup to 57.8 g m−2 d−1 of sediment on the surface. Sediments from mounds werecoarser, better sorted and showed a significantly higher amount of organic matter thansurrounding bottom sediments. An experiment using bedload traps deployed in a largearea dominated by this species showed that the particle size of the sediment from moundswere larger than those transported by bedload. This pattern suggests that cohesive, organicallyrich sediment deposited at the surface by polychaete feeding stabilizes the sediment.Under conditions of low environmental energy, bioturbation by L. acuta may promotesediment stability.One