Community Structure of Soft‐Bottom Macrobenthos of the Newport Submarine Canyon, California

Abstract

Abstract. The hypothesis that benthic community structure of soft‐bottom macrobenthos does not change throughout the Newport Submarine Canyon, California was tested with a set of quantitative Van Veen (0.1 m2) samples down the canyon axis. There was a marked break in community structure between Station C4 (187 m) and Station C5 (324 m). Comparison of the present study with work conducted earlier indicates that mean number of species, abundance, and biomass were not significantly different between 1962 and 1978. Within the canyon, species diversity was high compared to 12 other southern California canyons. This difference was mainly due to sampling effort and the inactive nature of the Newport Canyon.SummaryOver 500 species are identified from Newport Canyon, California from 1978 to 1990. The diversity of soft‐bottom macrobenthos in shallow to intermediate depths of Newport Canyon is much higher than in other southern California canyons (Hartman, 1963). This difference is mainly due to sampling effort and the inactive nature of Newport Canyon which facilitates the maturation of soft‐bottom communities; in contrast to active canyons which through turbidity currents frequently disrupt the water‐sediment interface. Conditions within Newport Canyon have been stable for benthic community structure for at least 16 years and probably closer to 25 years. The hypothesis examined here shows that community structure is not homogeneous with depth along its axis, but has a marked break between 187 m and 324 m. Finally, we are now in a position to examine hypotheses concerning the effects of an ocean outfall on benthic community structure between the shelf and the canyon.