Does the presence of the SW Atlantic burrowing crab Chasmagnathus granulatus Dana affect predator-prey interaction between shorebirds and polychaetes?

PALOMO, M. G.; BOTTO, F; NAVARRO, D; ESCAPA, M., ; IRIBARNE, O.

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

ELSEVIER SCIENCE BV

Año: 2003 vol. 290 p. 211 - 228

0022-0981

The burrowing crab Chasmagnathus granulatus is an important bioturbator that generates denseburrow assemblages (crab beds) characteristic of intertidal habitats of SW Atlantic estuaries. Crabbioturbation affects the topography and hydrodynamics of the sediment, increasing sediment waterand organic matter content, decreasing sediment hardness and changing the grain size frequencydistribution. In this study, we found that burrowing crabs can decrease the impact of predation byshorebirds on polychaetes. The polychaete Laeonereis acuta Treadwell has U-shaped burrows outsidecrab beds, which are associated with surface deposit-feeding while their burrows are mainly I-shapedinside which is associated with subsurface deposit feeding behavior. This pattern is likely the result oflarger vertical sediment mixing inside crab beds due to crab burrowing. As a result of their feedingstrategy, polychaetes appear on the surface more often outside crab beds, which increases theiravailability for shorebirds. In addition, shorebird species differentially use crab beds. The WhiterumpedSandpiper, Calidris fuscicollis Vieillot, preferentially forage outside crab beds, meanwhile theTwo-banded Plover Charadrius falklandicus Latham forage more frequently inside crab beds.However, experiments excluding shorebirds inside and outside crab beds showed negative effects ofshorebirds only outside crab beds. Thus, our results show that the SW Atlantic burrowing crab C.granulatus affects the strength of the predator–prey interaction between shorebirds and polychaetes.