Giant Green Anemones (Anthopleura xanthogrammica) are the most spectacular sea anemones we have seen on the southern Oregon coast. They are found in the lowest tide zone where they are rarely out of water. They can grow to ten inches in diameter and live over 100 years!
The Giant Green Anemone is usually a solitary animal, but we have found large numbers of them together at Myers Creek Beach (approximately ten miles south of Gold Beach) and Nesika Beach (7 miles north of Gold Beach). They are most often found living below mussel beds (see photo below), presumably because they are the beneficiary of mussels that become dislodged by the surf. In addition to mussels, Giant Green Anemones eat crabs, sea urchins, and we have personally seen one eat an Ochre Star.
- Tide-pooling hint: When exploring the rocky shores, bring along some raw fish or shrimp (Rogue Outdoor Store at north end of Gold Beach sells pint size containers of fish-bait). When you find a Giant Green Anemone with its tentacles outstretched, place a piece of the bait on one of the tentacles….it is interesting to see how fast the anemone will maneuver the food into its mouth.
There are approximately 30 Giant Green Anemones in the photo below. The large green pendulous columns hanging off the rocks above the water-line with their tentacles retracted into their hollow body cavities, look totally different than their counterparts submerged with tentacles outstretched. (The two reddish and brownish colored columns in the center of the photo are another sea anemone species, Urticina coriacea, commonly called Painted Urticina).
Giant Green Anemones living in sunlight have a uniform bright green color, the result of a symbiotic (beneficial to both) relationship with algae (either zoochlorellae or zooxanthellae, or both). Algae are plants and require sunlight (photosynthesis) to live and reproduce. The Giant Green Anemone obliges by maneuvering either toward or away from sunlight to provide optimium lighting for the algae. In return, the algae provide a nutrition source for the anemone. Giant Green Anemones found in caves or other shaded areas are smaller, and lack both the symbiotic algae and the vibrant green color.