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What Types of Organisms Live on Saltwater Rocks?

Saltwater rocks occur near the shore, in tide pools and as coral reefs. The ocean floor is made up of different types of rocks--sedimentary, metamorphic and igneous. Studying saltwater rocks and their organisms helps scientists determine the history of a region as each new layer traps plants and animals living in and on the rocks at the time. Several types of invertebrates, crustaceans and plankton inhabit saltwater rocks.

Coral
- When the invertebrate organism called a coral polyp attaches to a saltwater rock, it begins to divide and multiply. Over long periods of time this coral structure grows larger and larger, becoming a coral reef. Algae grow on the reef, turning the translucent coral different colors.
  
  The coral is a "living rock". It eats algae byproducts, very small fish and zooplankton. According to nationalgeographic.com, coral reef communities support one-quarter of all the ocean's organisms. Aquarists often put coral, such as the easy-to-grow button polyp, in saltwater fish tanks.
Sea Anemones
- A predacious carnivore, the sea anemone attaches to coral reefs and saltwater rocks, waiting for fish to capture and eat. Although anemones can be as small as half an inch or as large as six feet across, they are typically the size of a teacup, according to nationalgeographic.com. These colorful invertebrates have petal-like tentacles surrounding a central mouth. If a fish comes too close, the sea anemone paralyzes it with its stinger, then guides the meal into its open mouth. Sea anemones remain attached to their saltwater rocks for up to 50 years.
Barnacles
- Bane to boat owners everywhere is the barnacle. Although its natural habitat is saltwater rocks, this small crustacean will adhere to anything substantial, including the bottoms of boats, crabs and whales. The barnacle feeds on passing phytoplankton, gathering these tiny organisms into its mouth with hair-like tentacles. Barnacles use the extremely strong glue they produce to remain attached to their chosen surface for their entire life. According to the University of Rhode Island, the glue of the barnacle is being studied for use in dentistry.
Worms
- Sea worms such as the fat innkeeper worm, bloodworm and ice cream cone worm, can change the structure of saltwater rock. Some worms cement grains of sand together into long tubes that other organisms use as oxygen and water straws. Other marine organisms colonize these stationary rock tubes. The bloodworm mixes sediments, enriching the sea bottom. Sea worms create suitable areas for coral to build reefs.

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