La Jolla Bay
Map SatelliteDue to the extraordinary range in depth and the variation in bottom substrates in the Bay, there are an unusual number of marine communities. The most notable features, however, are the submarine canyons, La Jolla (see San Diego – La Jolla Ecological Reserve) and its tributary, Scripps, which have their counterparts in the steep-sided canyons cutting the adjacent coastal cliffs.
Scripps Submarine Canyon, the most studied in the world, begins some 200 meters (650 feet) offshore (see Scripps Shoreline-Underwater Reserve) and runs in almost a straight line westerly 2 kilometers (1.25 miles) to its junction with La Jolla Canyon at a depth of 275 meters (900 feet). Beginning in a sand chute at about 5 meters (15 feet) the canyon walls gradually steepen until at 15 meters (50 feet) a rock gorge begins; almost vertical, and in some places overhanging, walls up to 150 meters (500 feet) high are found throughout the length of the canyon. There are several hanging valleys and sand chutes in the main canyon. The main tributary forms a gorge which narrows to less than 2 meters (6 feet) a few meters from its junction with the canyon at a depth of 50 meters (175 feet).
The canyon floor is sandy and in its upper reaches supports dense stands of eel grass, Zostera marina, and giant kelp, Macrocystis pyrifera. On the vertical walls a number of animal species are found including the unusual anemone Metridium senile and the orange sponge, Ficulina suberea.
At the southern end of the Bay, off The Cove and Point La Jolla, there are rocky reefs extending out from the intertidal to depths of 15 meters (50 feet) and more. There are numerous submarine arches, caves and other rock formations off the Point which, itself, is an outcrop of a hard Cretaceous, concretionary sandstone. The bottom changes from reef to rock rubble, with kelp to clean sand within 100 meters (330 feet) of the shore.
The nearly vertical reef walls support a variety of starfish, sponges and coelenterates and other invertebrates. Off the Point is the only known Southern California site of the yellow sponge, Polymastia pachymastia. Unique large colonies of phoronids can be found in the deeper water. Downwelling encourages the development of warm-water assemblages in the shallower waters.
A wide variety of fish is found in the kelp and reef areas including garibaldi, Hypsypops rubicundus, opaleye, Girella nigricans, and scythemarked butterfly fish, Chaetodon falcifer. Schools of juvenile kelp bass, Paralabrax clathratus, are found in the shoal waters, indicating a possible nursery. Squid are common (see San Diego – La Jolla Ecological Reserve). The California gray whale, Eschrichtius glaucus, is frequently sighted during migration.
Among the algae found in the Bay are Eisenia arborea, Egregia laevigata, Polyopes bushiae, Dictyota flabellata, Pelagophycus porra, Laminaria farlowii, Drouetia peltata, Gelidium cartilagineum and Rhodymenia spp.
Integrity: The sections of La Jolla Bay covered here are not in the protected zones, and the nearshore and tidal areas are suffering the impact of divers.
Use: Research, educational, observational.
Ref: 1958. A Possible Ecological Effect of Upwelling in a Submarine Canyon. Nature No. 178, pp.497-98.
Shepard, F. P. 1949. Terrestrial Topography of Submarine Canyons Revealed by Diving. Bull. Geo. Soc. Amer. No. 60, pp. 1,597-1,612.
December 1975
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman