UC San Diego Library – Scripps Digital Collection

This is the third in a continuing series of marine environment surveys conducted by the California Department of Fish and Game in cooperation with the State's Regional Water Quality Control Boards.

During February and March, 1965, Department scuba diving biologists made an ecological investigation off the western shore of Point Loma, San Diego County (into water depths of 100 feet). Data from this study, conducted for the San Diego Regional Water Quality Control Board, are to be used in evaluating the effects of a submarine outfall discharge on the marine life in the area.

Twenty diving and four intertidal stations were occupied along four transects run perpendicular to shore. A modified transect-quadrat method of survey was employed to sample the biota both quantitatively and qualitatively. In addition, three orange-peel grab samples were taken near the outfall terminus (200-foot depth) primarily to determine sludge build-up.

The animal and plant assemblages were both lush and varied. The recorded species, numbers and diversities appeared typical for this general area, water depth, and bottom type. Bathymetrically, the greatest species diversity occurred in the 60- to 80-foot depths—the least in the 20. Geographically, species diversity was greatest in the central portions of the study area, and the least diverse in the northern. This correlated with the height of the bottom relief.

Although it is difficult to make comparisons with prior studies, because of different sampling techniques, the area's general biotic assemblages appeared similar, and except for the occurrence of Capitella capitata (a "pollution-tolerant" polychaete worm) at the outfall terminus, no adverse changes, directly attributable to outfall operations, were apparent in 1965. Five plants and 14 animals are deemed particularly hardy; these index species should be closely monitored in future studies to detect changes in their abundance relative to associated species.

Similar ecological studies should be carried out at least annually to record biotic changes which may be relative to the outfall's operation.