Distribution and ecology of deep-water mollusks from the continental slope,southeastern Gulf of California,Mexico

Specimens of deep-water mollusks were collected with a bottom dredge in the SE Gulf of California during four cruises (TALUD project) in 2000–2001. A total of 24 species (16 Pelecypoda, 5 Gastropoda, and 3 Scaphopoda) were collected. Analyses of environmental data (depth, epibenthic temperature and oxygen content, sediment texture and organic matter content) associated with each record indicated that the community diversity of these deep-water mollusks was related to oxygen concentration and density was correlated with depth. A canonical correspondence analysis (CCA) indicated that the five environmental variables explained 53.8% of observed variance in the model. In a multiple regression analysis, density (ind l⁻¹) was best correlated with dissolved oxygen concentration (R = −0.25), followed by temperature (R = −0.20), organic matter content (R = −0.15), and depth (R = −0.12). As oxygen best explained variance in the CCA it was selected to perform a single correspondence analysis (CA) using the most abundant and frequent species (two Pelecypoda and three Scapophoda). The analysis shows that pelecypods occur in near anoxic values while scaphopods occur in intermediate oxygen concentrations.