BLACK REEFS: WHEN SHIPS HIT THE REEF

Black reefs are associated with shipwrecks or other debris in the Central Pacific. These sites are interesting both from a conservation and scientific point of view. As a conservation issue, they are amazingly destructive. Kingman, one of the jewels of the USA coral reefs, has lost >1 km of the lagoon in less than 3 years. An old wreck on Fanning atoll has killed about 10% of their reef. Visually, the black reefs are some of the eeriest places I've ever seen. The bottom is completely covered in different algae (including cyanobacterial mats), the water is filled with marine snow, and dark precipitate on the benthos (probably sulfur). We just published a paper in ISME where we have recreate the precipitate, cloudiness, and coral death in microcosms by combining rubble from the black reefs, with corals and an iron addition. Addition of antibiotics blocks the coral death, precipitate, and marine snow, suggesting a microbial role.

The black reefs are probably caused by iron-enrichment from the wrecks and debris. We think black reefs are specific to non-emergent coral reefs, where iron is a limiting nutrient. Our current model is that iron stimulation of algae leads to increased microbial activity and coral death. In support of this, metagenomic analysis of the microbial community showed an enrichment of iron-related pathogenicity factors.

If you are interested in the science, the please see the ISME journal, click here.

If you are interested in conservation, then please help us petition the congress to support removal of the wrecks and debris. Please contact Emily Douce at the Marine Conservation Biology Institute ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).

To see how messed up these sites are, please look at the National Geographic write up, click here.