Abstract

MENDEZ, Nuria  and  GREEN RUIZ, María. Superficial sediments and their relation to polychaete families in a subtropical embayment, Mexico. Rev. biol. trop [online]. 1998, vol.46, n.2, pp.229-236. ISSN 0034-7744.

The soft bottoms in front of Mazatlan Bay and "Isla de la Piedra" Peninsula were studied to produce maps (depth, grain size and organic matter content in sediments). Sixty samples were obtained with a 30 x 30 van Veen grab (4-21 m depth) and polychaetewere extracted from 21 subsamples. Grain size ranged from -1.05 phi (gravel) to 3.81 phi (very fine sand), with fine sand predominating. Organic matter content in sediment was 0.91-3.06 % (most values = 1-2 %). Thirty polychaete families (905 individuals/m2 in mean) were found, and Cirratulidae, Spionidae, Onuphidae, and Pilargiidae were dominant. Pearson's correlation of grain size, organic matter and depth proved significant (p<0.01; p<0.02), confirming the observed relationships of distribution patterns in the area. A Principal Component Analysis showed the association of several families to depth (Factor 1), to grain size (Factor 2), and to organic matter (Factor 3). Nevertheless, the distribution of polychaete families in the area may be governed by the combination of the three abiotic variables. Results indicated that abiotic and biotic variables have not changed considerably since 1980

Keywords : Sediments; grain size; organic matter; polychaetes; Gulf of California; Western Mexico.