The small shark is named for its distinct black-tipped fins. Not to be confused with the blacktip shark, a larger species with similar fin coloration, the blacktip reef shark can be found in shallow inshore waters throughout the Indo-Pacific, including coral reefs, reef flats and near drop offs. It may be seen in mangrove areas and even freshwater environments near to shore, moving in and out with the tide. The blacktip reef shark feeds primarily on fish, including many common reef fishes, but will also consume crustaceans, mollusks, and even snakes!
Reef sharks play a major role in shaping Caribbean reef communities. As the top predators of the reef and indicator species for marine ecosystems, they help maintain the delicate balance of marine life in reef environments. Reef sharks are highly valued for their meat, leather, liver oil, and fishmeal, which make them prone to overfishing and targeting. Yet, their importance for the tourism industry makes them more valuable alive than dead. In 2011, Honduras declared its waters to be a permanent sanctuary for sharks, making fishing for these species completely forbidden.
Cyanobacteria do not have skeletons and individuals are microscopic. Cyanobacteria can encourage the precipitation or accumulation of calcium carbonate to produce distinct sediment bodies in composition that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today (stromatolites are microbial mounds with a laminated internal structure). Bryozoans and crinoids, common contributors to marine sediments during the Mississippian (for example), produced a very different kind of mound. Bryozoans are small and the skeletons of crinoids disintegrate. However, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief.
A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Many reefs result from abiotic processes (i.e. deposition of sand, wave erosion planing down rock outcrops, and other natural processes), but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae.