Colors Go Wild
               Beneath the Waves

Underwater creatures found offshore come in brilliant hues, and the reasons are as varied as the creatures.

anemone

Story and Photos by Joanne Huemoeller

It's a stunning sight fully orchestrated by nature,
a wallpaper of marine organisms covering what once was just a rocky reef wall. Strawberry anemones have colonized below the mid-intertidal while a brilliant giant green sea anemone is attached in the upper, sunlit zone. Bright orange sea cucumbers dwell in the crevices. Nearby is a colony of encrusting cobalt blue sponge. A brick red gumboot chiton dines on red algae while its cousin, the pink lined chiton, feeds on pink coralline algae. Burgundy and green striped plumes of a northern feather duster worm emerge to filter feed next to the vivid orange plumes of a similar species. Vermilion sea stars roam the lower reaches of the wall while purple, yellow, and orange ochre stars feed on mussels above. Just off the wall, distinctly patterned orange and black tiger rockfish hang in the water column. And the commonality here is? Color.

Off Oregon's shoreline is an amazing display of brilliant color. The role color plays in the ocean is both simple and complex, understood and a mystery.

Color can warn of foul taste and toxicity. Some nudibranch species are masters of this adaptation. No attempting to "blend in" for these guys; they advertise their presence with justifiable confidence.

Color can camouflage as well, both cryptically and disruptively. Feeding on red sponge, a red dorid sea slug becomes one with its environment. Tiger rockfish use disruptive coloration, bands of contrasting colors, to disguise their body's outline.

At depth, where longer red and yellow wavelengths are first to be absorbed, the vermilion rockfish and the vermilion sea star are not the standouts they would be in the upper sunlit zones. They fade, instead, to a much more concealing olive green.

There is one simple use of color that is so ingenious, it cannot go without mention. Fish, lighter on their bellies and darker on their dorsal surface, are employing countershading and lessen their chances of being noticed by predators from both above and below. When seen from above, their dark topside blends into the darker deep water below. When seen from below, their lighter belly blends in with the brighter sunlit waters above.

But the role of protective coloring becomes more elusive when we consider that not all predators have a high degree of visual acuity or color discrimination. Protective coloring can only be effective if one's predators use visual signals to detect prey.

We do know that safeguarding is not the only role color plays in the ocean. Symbiotic algae living within the tissues of a giant green anemone are responsible for the anemone's brilliant green color. Anemones attached to a rock where sunlight is limited and photosynthesis impossible will be yellow.

Marine color can also be enigmatic. The brilliantly colored ochre star is clearly visible in the sunlit intertidal zones where it spends much of its life feeding on mussels. Its coloration does not offer camouflage or send a warning of foul taste. Any biological purpose to its color remains a mystery.

So what is the role of color in the ocean? There is no one answer. It can be simple, as in the case of the symbiotic relationship between algae and the green sea anemone. It can be more complex, as in the case of an advertising nudibranch. It can be well understood as in the case of countershading. And it can be a mystery as in the case of the ochre star. What we do know is that color in the ocean is spectacular!

Spanish Shawl Nudibranch

The bright coloration of the Spanish shawl nudibranch warns of foul taste (above). The fish-eating anemone’s sturdy tentacles help it catch shrimp and small fish (below).

Anemone

Oregon Coast November/December 2007

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