. Bulletin. Science. RARE SPECIES IN MARINE MONITORING 93. ° Fig. 1. Benthic sampling stations from the San Pedro Shelf, California. (1989) expressed the view that in most unstressed communities there are many rare species contributing to high species richness. Recalling our earlier character- ization of the relative vulnerability of rare species to natural and anthropogenic stresses compared to common species, the number of rare species might be ex- pected to decline towards an ocean outfall (Hummel et al. 1995; Cao et al. 1998). Moreover, stress may also be imposed by increased abu
. Bulletin. Science. RARE SPECIES IN MARINE MONITORING 93. ° Fig. 1. Benthic sampling stations from the San Pedro Shelf, California. (1989) expressed the view that in most unstressed communities there are many rare species contributing to high species richness. Recalling our earlier character- ization of the relative vulnerability of rare species to natural and anthropogenic stresses compared to common species, the number of rare species might be ex- pected to decline towards an ocean outfall (Hummel et al. 1995; Cao et al. 1998). Moreover, stress may also be imposed by increased abundance of organisms due to organic enrichment. It occurred to one of the authors (TG), that if rare species are more responsive to stress than common ones, the former should be included on a more regular basis as a tool in marine monitoring. This would greatly elevate their ecological significance, and serve as a stimulus fostering studies of natural history and population dynamics of species generally ignored for this purpose. Accordingly, we examined the proposition that the number of rare species should be lower in the vicinity of an ocean outfall. Materials and Methods Field.—From 1985 to the present the Districts has collected benthic samples of sediment and macrobenthic invertebrates with a double yoked m2 Van Veen grab from an array of stations on the San Pedro Shelf, California (Fig. 1). Sam- pling stations were located by Loran C and/or GPS ( + or — 15 m) and samples were sieved through a mm mesh screen which is the accepted mesh size in the SCB. Specimens were fixed in 10% buffered formalin and subsequently trans- ferred to 70% ethanol in preparation for laboratory analyses. From 1985 to the present the Districts has sampled annually (summer) 40 stations (N = 1) extending from 30 m to 324 m, and thirteen 60 m stations (N. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration
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