Canary in a coal mine is an oft-used metaphor when it comes to Global Warming and there are (sadly) many canaries out there. Dying reefs are a prominent canary — not just for for GW, but also CO2 pollution causing increasing acidification of the oceans.
We’ve tried many remediation techniques around the globe, from dumping concrete blocks and construction waste, old tires, and sinking 
retired Navy ships. Some with success, some less triumphantly.
Biorock® offers a different path, one that looks to have real possibilities. It applies an electric charge, “causing dissolved minerals to crystallize on structures, growing into a white limestone similar to that which naturally makes up coral reefs and tropical white sand beaches.” As per Biorock®‘s own graphics, renewable (solar or wave buoy) power could provide all the required electricity without the need for creating some form of infrastructure to bring power from shore.
Biorock® is not some form of laboratory concept, but has had numerous demonstration 
projects around the world that have shown enhanced coral growth rates, higher survival rates for corals than nearby ‘natural’ systems facing similar environmental stresses. Perhaps this is why the Global Coral Reef Alliance (GCRA) has licensed Biorock®.
There is even a YouTube collection of Biorock® related videos. Such as this one re Karang Lestari. EcoGeek terrain, without a doubt. Some wonderful reef photography off Bali, serious discussion of the threats and damage to the reefs, and discussion of a technology that is proving to have a real impact in remediating the damage to those reefs.