Manta rays and whitetip reef sharks glide past socially distanced visitors at Rio de Janeiro’s hangar-sized AquaRio aquarium. In a laboratory upstairs, above the main gallery, a new experiment is underway, one that marine scientists hope will enhance the survival prospects of the world’s coral reefs. Twenty rectangular aquarium tanks, each about 20 centimeters wide, are arranged in a grid on the fourth floor. Each one houses a colorful assortment of coral fragments.

The ocean’s stable health is an important component that upholds the climate’s behavior and life on Earth. A key indicator of that health? Coral reefs, also known as the marine "canaries in the coal mine."

Coral bleaching due to climate change is a major concern among ocean researchers. Record ocean temperatures during 2014-2017 triggered a mass bleaching event around the globe, a sign that this issue is becoming more dire.

A simple but powerful idea is to improve the health of corals using cocktails of beneficial bacteria. The strategy is being explored as part of global scientific efforts to help corals become stronger, more stress resistant and more likely to survive bleaching events associated with climate change. Corals rely on bacterial and algal symbionts to provide nutrients, energy (through photosynthesis), toxin regulation and protection against pathogenic attacks.