Educational Media Reviews Online

Coral reefs have been in existence for over 400 million years and are home to a diverse array of colorful tropical fish. Cemented together in limestone skeletons, coral reefs are composed of polyps and their symbiotic blue-green algae. Reefs expand in size as new polyps are added to the existing structure. However, reefs have a very narrow thermal tolerance and 1998 witnessed very extensive coral mass mortality. In some cases, losses of more than 90% of the coral cover were reported, suggesting that coral reefs are "silent sentinels" signaling the onset of global warming.

Silent Sentinels will be a very useful tool for educators because it describes the current environmental plight of corals while providing an excellent description of coral reef biology that will be understood by the entire target audience (grades 7-12, college, adult). The viewer learns how S.C.U.B.A. technology was first employed to study coral reefs as well as how the coral polyps obtain carbon dioxide from their symbiotic algae. The film builds on this basic knowledge and provides a very clear description of how temperature and sunlight can combine to destroy algae and cause coral bleaching. While current coral losses are dramatic, the film also describes how corals may, in some cases, recover from the loss of their symbiotic algae.

The film combines interviews with coral reef experts and excellent underwater footage from the Great Barrier Reef, Scott Reef, and Caribbean waters to thoroughly explain not only the current coral reef losses but also the past catastrophic coral losses and how this organism has coped with climate change over time. In just one hour, the viewer will leave with a very good understanding of the coral reef biology and the effects that warmer ocean waters are having on coral reef inhabitants.

There are literally dozens of videos available that relate to coral reefs, but "Silent Sentinel" has won numerous awards and belongs in every school, college and public library. It is an excellent educational film because it incorporates both biology and environmental science and it is very highly recommended.