At low tide, water retained between the sand particles is filled with millions of microscopic diatoms and zooplankton upon which the buried bivalves feed, using long siphons that reach to the sand surface. Fine screens within the siphons filter out sand particles by allow the passage of water and suspended organic material that provide an abundant food supply for the filter- feeding bivalves. Razor clams, surf clams and coquina clams are common burrowers along California beaches. Pismo clams occupy a special niche in the surf zone of Central California beaches, well-adapted to the crashing surf by nature of their large, heavy shells, which act as anchors. Inland from the surf zone, sand craves scavenge in the sun-dried kelp and bury in the sand, using their antennae to rake food particles to their mouths.
Kelp flies, wrack flies, rove beetles, tiger beetles, and dune beetles ream the beach foreshore.
The dry upper beach is inhabited by air-breathing pill buys and beach hoppers. Numerous beetle species inhabit the dunes, some burrowing in the sand during the day to escape predators and the heat. The natural process of beach building and erosion has been altered by extensive development of the California coast. Prior to development, natural loss of sand from beaches, largely to dunes and submarine canyons, and natural sand supply, mostly from rivers and streams, were in rough balance. The damming of rivers alone has reduced half of the natural sand supply to beaches from Santa Barbara to Mexico.