Once upon a time, when I first came to St. John some 40 years ago, the reefs were extremely colorful. Much has changed since then and the abundant hard corals that provided so much of the color have been severely depleted and those that remain are often unhealthy. Now it seems that most of the vibrant colors of the reef come from sponges, which can be seen in a multitude of varying colors, shapes and sizes.
Sponges, in case you weren’t aware, are animals, as are most of the creatures that make up the coral reef such as all the hard corals, the so called soft corals or gorgonians like sea fans and sea rods, and the sponge-like tunicates that often encrust rocks dead coral. As a matter of fact, the only plants on the reef that come to mind are algae and sea grasses.
Sponges are the simplest of the multicellular animals. Lacking any real organs, they survive by taking in water through small pores, filtering out the nutrients and oxygen and expelling the rest through the more visible larger openings.
All about St John in the beautiful US Virgin Islands (USVI) American Paradise