Influence of beach morphodynamics on bivalve Donax hanleyanus and Mesodesma mactroides populations in Argentina

THOMPSON GUSTAVO; SANCHEZ DE BOCK MARIANA

MARINE ECOLOGY-PUBBLICAZIONI DELLA STAZIONE ZOOLOGICA DI NAPOLI I

Blackwell Wissenschafts-Verlag

Año: 2009 vol. 30 p. 198 - 211

0173-9565

Five exposed microtidal sandy beaches of north-eastern Buenos Aires (Argentina) were analysed to evaluate the influence of coastal dynamics on the abundance of the intertidal clams Donax hanleyanus and Mesodesma mactroides over a one-year period. The physical characterisation of each beach was performed using fifteen environmental variables and six morphodynamic indices. The population densities of both clam species were estimated by the number of individuals per strip-transect. Analysis of similarities revealed a significant multivariate environmental difference among beaches, which could be aggregated into a northern and a southern group. The former group was characterised by an intermediate morphodynamic state and by having, in general, high density values for both clam species. The latter was composed of beaches with an intermediate reflective state and showed, in general, low density values. Beach Index and Area showed the lowest temporal variation. Total density values, as well as density values of recruits and adults of D. hanleyanus and M. mactroides did not follow a north-south latitudinal gradient. Spatial and temporal fluctuations of density values were best explained by changes in individual physical variables rather than by changes in composite indices.