Categorized | Featured, Sci-Tech

Coral bleaching watch begins for Northwestern Hawaiian Islands


Papahanaumokuakea Marine National Monument (PMNM) is one of the most pristine and best protected coral reef ecosystems in the world. While PMNM’s management is designed to best support the ecosystem’s resilience to climate change, these measures cannot completely prevent damage from climate change.

One of the effects of climate change is to increase the risk of reef damage through mass coral bleaching events. Mass coral bleaching occurs when unusually warm water temperatures disrupt the relationship between corals and the symbiotic microscopic algae that live within their tissues.

Temperature stress causes the coral to expel the algae, and the reef appears white or “bleached” as its calcium carbonate skeleton becomes visible. Coral bleaching was recorded in PMNM in 2002 and 2004, and is likely to occur again in the future.

Papahanaumokuakea Marine National Monument is co-managed through a partnership of the Department of the Interior’s U.S. Fish and Wildlife Service, the Commerce Department’s National Oceanic and Atmospheric Administration, and the State of Hawaii.

PMNM works with a network of leading scientists to assess bleaching risks and impacts by monitoring climate forecasts, sea temperatures, and coral conditions throughout the bleaching season (July-November).

2010 Forecast

Based on available information, the threat of widespread coral bleaching within PMNM is currently rated as low to moderate.

Globally, 2010 has been a significant year for mass coral bleaching. Severe events in Thailand, Malaysia, and Indonesia have caused up to 100% bleaching in some areas, resulting in high levels of coral mortality. The regional heat event that caused this extreme event in Southeast Asia has recently moved toward Micronesia, with reports of bleaching already reported in Palau.

Climate forecasts raise concern that a similar heating event may warm sea temperatures in PMNM beyond bleaching thresholds.

Predictions developed by NOAA’s Coral Reef Watch Program suggest that the bleaching risk is greatest to Papahanaumokuakea’s northern atolls: Kure, Pearl and Hermes, and Midway; the highest temperature stress is likely to occur in September 2010.

However, local weather conditions, including either storms or doldrums, will strongly influence the actual sea temperatures and could either prevent or worsen a mass bleaching event.

Current measurements of sea temperature by both satellites and in-water instruments indicate slightly above average temperatures and a very minor accumulation of heat stress.

Research cruises in August and September will provide an update on sea temperatures and coral condition, which will be described in subsequent condition reports.

— Find out more:

Click to access NWHI_Ch10_C.pdf

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