The Bleaching of

Our Coral Reefs

A visual exploration of coral bleaching

in the Pacific Ocean through

Smithsonian imagery

Pacific Ocean Bleaching Map*

Click to start exploring top bleached corals in the Pacific

*Map not to scale

About Coral Bleaching Smithsonian's Contribution

What Causes Coral Bleaching

Climate change is the greatest threat to coral reef ecosystems, driven by greenhouse gas emissions that warm the atmosphere and oceans. Rising temperatures have led to more frequent coral bleaching events and disease outbreaks. Additionally, ocean acidification—caused by absorbed carbon dioxide—reduces calcification rates in reef-building organisms, altering seawater chemistry.

Other effects include sea level rise, intensified tropical storms, and disrupted ocean circulation, all of which severely impact coral ecosystems and the essential services they provide to people worldwide.

How Chemicals Trigger Coral Bleaching

However, there are also other major contributors that facilitate the bleaching of corals. Excess nitrogen and phosphorus, particularly when present in high nitrogen to phosphorus ratios, can significantly increase the susceptibility of corals to bleaching by creating nutrient imbalances that stress the symbiotic algae (zooxanthellae) living within the coral, making them more vulnerable to environmental stressors like rising temperatures. Essentially, too much nitrogen without enough phosphorus can lead to "nutrient starvation" for the algae, causing them to be expelled from the coral, resulting in bleaching.

Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1 Coral specimen 1

Showcasing the Smithsonian’s Coral Collections: A Global Treasure

This project showcases the extensive and meticulously documented coral collections housed at the Smithsonian's National Museum of Natural History, one of the largest in the world. The project adopts a black-and-white aesthetic to emphasize the fragile beauty of coral reefs and remind us that these assets could fade into history if we fail to address our carbon footprint.

The Smithsonian’s Contributions to Coral Reef Research

The Smithsonian's contributions to coral reef research and conservation are central to this narrative. Efforts like the Healthy Reefs for Healthy People Initiative monitor coral reef health, with improvements in some regions attributed to community and government interventions. The Smithsonian’s National Zoo and Conservation Biology Institute has pioneered coral cryopreservation, creating repositories containing 1 trillion frozen sperm and 3 billion larval cells from 16 species. Meanwhile, the Smithsonian Tropical Research Institute explores resilient "super corals" off Panama's coast, offering hope for the future of coral reefs.

The Intersection of Education and Conservation

Images used in the project are sourced from the Smithsonian, with additional data provided by NOAA and Copernicus Climate Data. Citations for the two missing coral images sourced from these databases are included for reference.