Naturalist Guide: Ocean

When it’s not foggy, the Point Arena-Stornetta Lands is an ideal place to watch the ocean life swimming along California’s coast. From November through May, migrating grey whales cling to the shoreline as they round the point on their migration between Alaska and Baja California. Harbor seals haul themselves onto the rocks, the ocean dripping from their coats, to nap in the sun. Just north of the Lighthouse is the mouth of the Garcia River, an estuary that connects freshwater habitat with the ocean. River otters swim through the river mouth to roll around in the sand and try their luck fishing in the sea. Chinook and coho salmon return from the ocean to the Garcia River to spawn. They swim upstream to lay their eggs, and the juvenile fish live in the river for a year before swimming out to the ocean.

Although it is easy to tell how windy this part of the coast is, it is surprising to learn how this affects the ocean. Like a giant fisherman throwing out chum, the headlands create a feeding frenzy for wildlife. The rocky point stretches out and catches the strong wind-driven current, pushing surface water out to sea and pulling up cold, nutrient-rich water from the ocean depths, in a process called upwelling. The Point Arena headland amplifies winds and currents, creating a massive upwelling zone that spreads nutrients hundreds of miles out to sea and down to Point Reyes. This nutrient-rich water feeds phytoplankton and kelp, which are the base of a bountiful food chain. Krill, a small shrimp-like crustacean, feed on phytoplankton and become the staple food for hundreds of different species, everything from small fish to giant whales.

adult harbor seal with pup
Adult harbor seal with pup.

Point Arena’s rocky shoreline and cold, nutrient-rich waters provide ideal growing conditions for bull kelp forests. Bull kelp is an alga that gets energy through photosynthesis and from nutrients in the water and is the foundation of a whole ecosystem. It is a staple food for small fish, abalone, and a host of other organisms that in turn become food for larger animals like harbor seals and sea stars. From the rocky holdfast on the ocean floor, all the way up to the surface, kelp provides habitat where creatures can live and raise their young. Many animals also temporarily shelter in bull kelp to cope with storms, rough waves, and predators. Grey whales and harbor seals will swim into kelp forests to escape from chasing orcas.

whales off the coast
Whales can be spotted close to shore from the bluff-top trail.

Unfortunately, a combination of ecological and oceanographic factors caused a dramatic reduction in kelp forests all along the north coast of California. From 2013 to 2016 a record-breaking marine heatwave massively disrupted this ecosystem, and scientists think that climate change is causing these extreme events to occur more frequently. Around this same time, a wasting disease killed most sea stars, an important local predator of purple urchins. Left unchecked, the purple urchin population exploded to 60 times higher than usual. Purple urchins are voracious consumers of kelp and they turned areas that used to support productive kelp forests into urchin barrens. Since 2013, kelp forests declined by more than 90% in northern California and this vital ecosystem is struggling to recover. In 2021, scientists observed a large amount of kelp forest regrowth, an unexpected but promising sign that will hopefully continue.

sea star surrounded by purple urchins
Sea star surrounded by purple urchins.

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