Effect of Spartina alterniflora on growth of the stout razor clam Tagelus plebeius in a SW Atlantic estuary

ADDINO M.,; MONTEMAYOR D.,; ESCAPA M.,; ALVAREZ F.,; VALIÑAS M.,; LOMOVASKY BETINA J.; IRIBARNE O.

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 463 p. 135 - 142

0022-0981

Organisms that produce epibenthic structures such as saltmarsh plants may play key roles in habitat functioning through their ecosystem engineering effects. Intertidal Spartina species are well known for modifying tidal hydrodynamic and sediment processes, affecting cohabiting infaunal organisms. The stout razor clam Tagelus plebeius is an infaunal filter-feeding species that inhabits a broad range of mudflats (MF) and Spartina saltmarshes (SM) along the West Atlantic coast. Through samplings and experiments conducted at the Bahía Blanca estuary (Argentina, 38º 47?S, 62º 20?W), we evaluated ecosystem engineer effects of Spartina alterniflora (due to changes in sediment and water characteristics) on somatic and shell growth of T. plebeius. Comparison of bulk sediment parameters indicated that sediment is more easily eroded in the SM than in the MF, while in the latter sediment is softer. In addition, food supply for clams (i.e., total particulate organic matter) showed higher values in the MF although percentage of organic matter in the water column was in general higher in SM. Samplings and a transplant experiment showed a higher shell growth and lower clam condition index (CI) in MF than in SM. However, the opposite pattern was found in SM, representing an uncoupling between shell and somatic growth with a positive effect of S. alterniflora on the CI of clams. Nevertheless, results of two other field experiments manipulating stems and roots of plants separately suggested that the effect of Spartina on clam?s CI was not due to the structural changes generated by plant presence itself, although a better food quality instead of food quantity, in SM may be implicated.