The moderate climate of California's central coast region helps make intertidal life at Ano Nuevo among the most luxuriant in the world. Air and sea temperatures vary far less from winter to summer than is true in other parts of the world. As a result of this and other factors, tide pools along the rocky shoreline teem with life. More than 300 species of invertebrates have been recorded at A o Nuevo, including an unusual number of rare species. Common life forms include clams, abalone, limpets, chitons, hermit crabs and flower-like anemones.
Tiny worms build huge honeycomb homes on shallow rocky ledges.
Nutrients from seal and sea lion wastes seem to fertilize the lush aquatic plant growth, so that rockfish and bottom fish abound in offshore waters. A o Nuevo Island and the adjacent mainland beaches make up one of the most important pinniped rookery and resting areas in central and northern California. Northern elephant seals are the largest, and, in many ways, the most impressive of these animals. Harbor seals are much smaller and quite wary and elusive. The tawny brown or yellowish Steller sea lions, which mate on the rocks around the island from mid August, are most often seen on the rocky outer portions of the island.