Soft-bottom mollusc assemblages in the Ría de Ares-Betanzos (Galicia, NW Spain) release_su3fv5z4zzd5bovkbfw4gu43ge

Abstract

The composition and spatial distribution of the mollusc fauna on the subtidal soft bottoms of the Ría de Ares-Betanzos (Galicia, NWSpain) were studied by means of semi-quantitative sampling and multivariate analyses. The faunal distribution in the ría seems to be mainly conditioned by a depth and grain size gradients, the latter defined by a increase in silt/clay and a decrease of coarser granulometric fractions from the mouth towards the margins and inner areas of the ría. Several assemblages were determined which could be defined according to the classic terms of 'community' and 'facies'. Sandy bottoms showed a '<em>Venus fasciata </em>community' in coarser sediments of the outer ría, while a '<em>Venus gallina </em>community' was found in fine sand at the center of the ría. The shallower and muddier sediments in the inner ría showed a mix of typical species from the '<em>Abra alba</em>' and the '<em>Venus gallina</em>' communities. However, two facies could be distinguished: the 'facies of <em>Ringicula auriculata-Pandora inaequivalvis</em>' in sediments with a greater fine sand content, and the 'facies of <em>Nassarius pygmaeus-Dentalium novemcostatum</em>' in the muddiest sediments.
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