Abstract
Abstract The RUM/ORB unmanned submersible system (Marine Physical Laboratory, Scripps Institution of Oceanography) was used at 1220-m depth to collect precisely located samples separated by distances from 0.1 to 500 m in the San Diego Trough, Southern California continental borderland. Newly developed spatial autocorrelation procedures from the field of quantitative geography were used on this irregularly spaced network of samples to test the statistical significance of the calculated autocorrelations. Scales less than 200 m showed little spatial autocorrelation in total numbers of macrofaunal individuals per sample. Density of Polyophthalamus sp. (Polychaeta, Opheliidae), however, displayed a complex autocorrelative pattern; ‘patches’ of individuals of similar size were observed. Ceratocephale pacifica (Polychaeta, Nereidae), on the other hand, showed negative spatial autocorrelation at the smallest inter-sample distance, perhaps indicative of territoriality. Vertical segregation among confamilial and congeneric species was observed in vertically sectioned subsamples. The majority (82%) of polychaetes, however, appear regularly to inhabit the uppermost centimeter of sediments, suggesting a refinement of current bioturbation models.
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