Their finding may help solve Darwin's famous 'coral reef paradox' - why immensely diverse reef ecosystems occur only in nutrient-poor waters.
Claudio Richter of the University of Bremen, Germany, and colleagues, have found a thriving microcosm of sponges and other organisms hidden within the cracks and crevices of Red Sea coral reefs. They discovered this using an underwater endoscope.
They describe their findings in this week's Nature.
| The team used an underwater endoscope to study coral reefs.
The wealth of organisms within the internal honeycomb of the reefs filter food out of the ocean, and excrete nutrients such as ammonia and phosphate into the reef.
The cave dwellers harness enough nutrients to provide a major food source for the coral, the team calculates.
They found more than 370 types of sponge and other filter-feeding organisms, many of which are likely to be completely new species.