Figure 1. Zones of sandy floor within the Monterey Bay, Gulf of the Farallones, and Cordell Bank National Marine Sanctuaries. [View Larger]
The lack of hard substrate and the shifting sand prevent algae from settling, therefore these vast sandy plains stretching in all directions appear to be lifeless deserts. However, looks can be deceiving.
InhabitantsMany organisms make their homes either on (i.e., epifaunal) or in (i.e., infaunal) the sediments.
In particular, two communities are organized along a gradient of wave-induced substrate motion:
- The crustacean zone: this shallower zone, characterized by strong water motion and sandy sediments, is occupied by small, mobile, deposit-feeding crustaceans.
- The polychaete zone: characterized by more stable, fine sand with a significant amount of mud, this deeper zone is dominated by polychaete worms living in relatively permanent tubes and burrows. Many other relatively sessile and suspension-feeding groups are also common here.
The width and depth limits of these two zones vary, depending on the strength of wave activity.
Three-colored top snail Calliostoma tricolor. Observed during a survey under the direction of Dr. John Pearse as part of a long-term monitoring project.
The California aglaja (Navanax inermis) is a species of predatory sea slug, a marine opisthobranch gastropod mollusk in the family Aglajidae and the order Cephalaspidea, the headshield slugs and bubble snails.
The most common natural disturbance in the sandy seafloor habitat is from wave action. Other disturbances are biotic - such as from the digging activities of feeding southern sea otters, Enhydra lutris.
MonitoringWithin the three northern California sanctuaries, monitoring efforts focused on the sandy floor are currently underway only in the Monterey Bay sanctuary.
Examples of related monitoring projects: