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NPAS warns of potential coral bleaching this summer

An example of coral bleaching. [SN file photo]
Source: National Park of American Samoa media release

Coral reefs are the most diverse marine environment on the planet, providing homes to hundreds of species of fish and coral. We depend on the reef for food, protection from storms, and recreation. Unfortunately, coral bleaching is considered one of the greatest threats to the world’s coral reef systems, and it is expected to happen more often as climate change continues. 

American Samoa experienced some coral bleaching on almost all reefs in 2015 and 2016 and bleaching is expected during this upcoming January. Bleaching can cause fish kills, coral death, and coral disease. Understanding bleaching and how it relates to high temperature events allows us to prepare for and attempt to lessen the impacts on our local environment.


Corals bleach when they become stressed because of the increase in water temperature, pollution, and exposure to too much sunlight. When corals bleach, the coral animal push out tiny colored algae (marine plant) that live in their cells causing the corals to turn white. The white coral you see as a result does not necessarily mean the coral is dead, but it is starving.

Corals rely on these colored algae for oxygen and food (energy), so if a coral remains bleached for long enough, it will die. Even when corals are capable of recovering from bleaching events, they often experience a decline in growth rates, reproductive potential, and overall health.


Our reefs continue to be threatened by negative impacts from people, such as leaking septic systems, illegal piggeries, and adding too much fertilizer to crops. The high amount of nutrients from these activities make their way into our ocean and damage the ecosystem by feeding large mats of algae (limu) that suffocate or harm corals.

This is why it is also important to protect fishes that eat algae (like Alogo, Poge, Ume-isu, Umelei) and help control algal overgrowth. The islands of Hawaii and Guam are both considering laws to limit the fishing of algae-eating fish while their reefs recover from the current bleaching events.

With good island stewardship we may be able to minimize the negative impact on our reefs here in American Samoa. We can help reduce the likelihood of bleaching events by minimizing human activities that produce the carbon emissions that drive climate change. With a little effort we can also help the reef quickly recover back to its current healthy state when bleaching events do occur.

Everyone can make a difference by not littering, making sure your septic system is up to date, reporting illegal piggeries, and protecting plant-eating fish like Alogo. Feel free to stop by the National Park office if you would like to learn more about climate change, coral bleaching, and how it will affect our environment.