STRUCTURE AND COMPOSITION OF THE POLYCHAETE ANNELID FAMILIES OF TODOS SANTOS BAY, BAJA CALIFORNIA, MEXICO
Rodríguez-Villanueva, V. & Díaz-Castañeda, V.
CICESE. Km 107 Highway Tij.-Ensenada Apdo. Postal 2732. Ensenada, B.C. Mexico
In October 1994, 39 stations were sampled using a van Veen grab (0.1 m²) in Todos Santos Bay, Baja California, with depths between 7 and 400 m. This was the first ecological and taxonomic study to cover almost the entire bay. 17,079 polychaetes were identified, which constituted 61% of the individuals in the total benthic macrofauna. 45 polychaete families were represented; the families Aphroditidae, Pholoidae and Fauveliopsidae were new records for Baja California. 56% of the organisms presented sedentary habit and 44% errant habit; the dominant trophic category was that of sedimentivorous polychaetes, followed by carnivores. The best represented families by density were: Capitellidae (520 org/0.1 m²), Spionidae (502 org/0.1 m²), Paraonidae (251 org/0.1 m²), Cirratulidae (189 org/0.1 m²), Ampharetidae (188 org/0.1 m²), Maldanidae (183 org/0.1 m²) and Nephtyidae (125org/0.1 m²). The most widely distributed families in the bay were Paraonidae and Nephtyidae. High values of the Shannon-Weaver index of diversity (2.21-4.14) and of Rigor-Predictability analysis (Alcolado, 1992) indicated that 70% of the study area was a favorable environment; especially the southern section of the bay. The remaining 30% of the area was being affected by influxes of residual waters and dredging of the associated port. Jaccard and Spearman's coefficients of association corroborated the elevated faunistic affinity across 82% of the bay. Along with the association coefficients, non-metric multidimensional scaling distinguished a submarine canyon area from the rest of the bay. Principal component analysis of environmental parameters showed the main factors driving polychaete faunal characteristics of the bay were depth, sediment grain size and organic matter content.