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Distribution of Brittlestar Amphiodia (Amphispina) spp. in the Southern California Bight in 1956 to 1959





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Brittlestars Amphiodia (Amphispina) spp., particularly Amphiodia (Amphispina) urtica (Lyman 1860), are of interest in southern California because they are rare or absent adjacent to municipal wastewater outfalls even where they are expected to be the community dominant. In the monitoring programs for the outfalls, impacts to benthic communities are determined by comparing abun- dances near the outfall to the abundance in "reference" areas. In order help define reference conditions, data from a survey conducted between 1956 and 1959 were used to determine the effect of latitude, depth and sediment grain size on the distribution and abundance of Amphiodia {Amphispina) spp. Brittlestars Amphiodia {Amphispina) spp. were most abundant in water depths of 48 to 102 m in sediments with median grain size between 0.035 and 0.093 mm, a diameter classified as coarse silt to very fine sand. Amphiodia {Amphispina) spp. were rarely collected in less than 15 or more than 85 m of water. The abundance of Amphiodia {Amphispina) spp. was generally lower north of Ventura than elsewhere in the Bight. The difference in abundance can, in part, be attributed to the character of the sediment. However, even in areas with suitable sediment, the abundance of Amphiodia {Amphispina) spp. north of Ventura was relatively low. The reason for this difference is unknown. It is also not known if Amphiodia {Amphispina) spp. are, at the present time, less abundant north of Ventura than elsewhere in the Bight.