The Intertidal Burrowing Crab Neohelice (=Chasmagnathus) granulata Positively Affects Foraging of Rodents in South Western Atlantic Salt Marshes.

ALEJANDRO CANEPUCCIA; M. SOL FANJUL; EUGENIA FANJUL; FLORENCIA BOTTO; OSCAR IRIBARNE

Estuaries and Coasts hasta el volumen 29 (2006) se denominaba Estuaries

Springer

Año: 2008 p. 520 - 530

1559-2723

 The role of positive and indirect interactions is often crucial in communities with intense abiotic stress such as salt marshes. The burrowing crab, Neohelice (=Chasmagnathus) granulata, is the dominant benthic macroinvertebrate of southwest Atlantic marshes (southern Brazil to Northern Argentinean Patagonia), having strong direct and indirect effects on marsh soil and, in consequence, on marsh vegetation and primary consumers.In this work, we investigate if this crab indirectly modifies habitat use by the granivorous rodents, Akodon azarae and Oligoryzomys flavescens, by increasing nutrient availability and thus enhancing seed production by the marsh plant Spartina densiflora. The study was conducted at the Mar Chiquita Coastal Lagoon, Argentina (37°32′ S). Rodent frequencies in S. densiflora were positively correlated with crab densities throughout the low and middle marsh. Additionally, the highest quality of S. densiflora and inflorescence density was recorded at the highest crab densities. Experimental manipulation of crab densities shows that N. granulata indirectly enhances the performance of S. densiflora (e.g., decreased fiber content and C/N ratios) and increases density of seeds. Moreover, N. granulata also facilitates S. densiflora seed availability to rodents by concentrating them in sediment mound at their burrows entrances. Experimental rodent exclusions showed that rodent species used S. densifloraseeds, a variable positively related to crab burrow density. Thus, our results show that N. granulate drives the granivorous rodent distribution and the intensity of seeds–rodent interaction trough facilitative and indirect interactions in marsh community