The California coastline supports a remarkable concentration of animal life, driven by unique oceanographic forces. The southward-flowing California Current brings cooler temperatures, and prevailing northwesterly winds cause coastal upwelling. This phenomenon pulls deeper, nutrient-rich water to the surface. The abundance of nutrients fuels a vast bloom of microscopic plant life, forming the base of a food web that sustains a diverse assembly of creatures from tiny invertebrates to massive whales.
Defining the California Coastal Ecosystem
The coastal region is not a single habitat but a series of interconnected zones, each supporting specialized animal communities. The Nearshore Pelagic Zone encompasses the open water just offshore, where migrating marine mammals and schooling fish find sustenance. Closer to the shoreline is the Intertidal Zone, the dynamic area between the high and low tide marks, including rocky shores and sandy beaches. Organisms here must tolerate extreme daily shifts from being submerged to being exposed to air, sun, and predators. Immediately adjacent to the ocean is the Coastal Scrub and Bluff Zone, the terrestrial area where sea cliffs and estuaries provide nesting and foraging grounds for many coastal bird species.
Iconic Marine Mammals and Nearshore Life
The cool, productive waters of the California Current attract many marine mammals.
California Sea Lions
California Sea Lions (Zalophus californianus) are a common sight, often congregating in noisy “haul-outs” on jetties and offshore buoys. These “eared seals” can rotate their rear flippers forward, allowing them to walk on land. Adult males are significantly larger than females, weighing up to 850 pounds, and possess a pronounced sagittal crest.
Northern Elephant Seals
The Northern Elephant Seal (Mirounga angustirostris) forms massive breeding colonies on remote beaches. Males sport a large, fleshy proboscis used for vocalizations and dominance displays. These seals are deep-diving specialists, spending up to nine months a year at sea and reaching depths of 1,000 to 2,000 feet during foraging dives. They come ashore only for breeding and an annual molting process.
Southern Sea Otters
The Southern Sea Otter (Enhydra lutris nereis) is a keystone species due to its diet of sea urchins, crabs, and mussels. By consuming sea urchins, which graze heavily on kelp, otters maintain the health of kelp forests that provide habitat for numerous other species. They are the smallest marine mammal in North America, weighing between 45 and 70 pounds, and are often seen resting on the water’s surface wrapped in strands of kelp.
Migratory Whales
Larger migratory species like the Gray Whale (Eschrichtius robustus) and Humpback Whale (Megaptera novaeangliae) are seasonal visitors. Gray whales undertake one of the longest migrations of any mammal, passing close to the California shore between their Arctic feeding grounds and breeding lagoons in Baja California. Humpback whales feed in these nutrient-rich waters, often exhibiting lunge-feeding behavior to capture schooling prey like anchovies and krill.
Life in the Intertidal Zone
The extreme conditions of the intertidal zone, alternately submerged and exposed, are home to a resilient community of invertebrates.
Mussels, such as the California Mussel (Mytilus californianus), form dense beds on rocky substrates. They use strong, silky byssal threads to anchor themselves against powerful wave action and are highly efficient filter-feeders. The Ochre Sea Star (Pisaster ochraceus) is a dominant predator, specializing in prying open mussel shells. Its presence prevents mussels from completely dominating the rock face, thereby creating space for smaller organisms like barnacles and limpets to settle. Barnacles are sedentary crustaceans that cement themselves to the rock, extending feathery appendages called cirri to filter-feed.
In tide pools, the Giant Green Anemone (Anthopleura xanthogrammica) appears as a large, solitary, flower-like animal. Its green color results from a symbiotic relationship with internal algae, and it uses stinging cells on its tentacles to capture small fish and crustaceans. Shore Crabs scuttle through crevices, foraging for algae and detritus. On sandy beaches, the Pacific Mole Crab (Emerita analoga) is common, burying rapidly into the sand and using its antennae to filter-feed on plankton in the swash zone.
Avian Residents of Coastal Bluffs and Estuaries
The coastal air is filled with birdlife, utilizing coastal habitats for nesting and feeding. The Brown Pelican (Pelecanus occidentalis) is a frequent sight, known for its plunge-diving technique to catch fish near the water’s surface. These large seabirds breed in colonies, with consistent nesting sites located on the Southern California Channel Islands.
Brandt’s Cormorants (Phalacrocorax penicillatus) are dark, sleek birds that nest in dense colonies on steep coastal cliffs and offshore rocks. They are exceptional divers, propelled by their webbed feet to chase fish up to 40 feet below the surface. They are often seen with their wings spread wide to dry because their feathers are not fully waterproof.
The Western Gull (Larus occidentalis) is an opportunistic scavenger that patrols the shoreline, feeding on marine life and scavenging refuse. It primarily breeds on offshore islands like the Farallones. Ospreys (Pandion haliaetus) are large, fish-eating raptors that construct stick nests on elevated structures near water sources, including estuaries and bays. Their diet is nearly 99% fish, which they catch by plunging feet-first into the water, aided by specialized barbed pads for gripping prey. Estuaries and mudflats attract migratory shorebirds, including the Western Sandpiper (Calidris mauri), which probes the soft substrate for invertebrates. These coastal areas serve as vital stopovers along the Pacific Flyway.