'%Healthy Reefs for Healthy People - A Guide to Indicators of Reef Health and Social Well-being in the Mesoamerican Reef Region%'%by Melanie McField and Patricia Kramer% of 38

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CORAL BLE ACHING INDE X

ORITY ON

D14

S FOR HEAL

What

What Is It?

BENCHMARK

No increase in the frequency of NOAA

The Tropical Ocean Coral Bleaching Indices provide

Bleaching Watches issued for the

near-real-time information about thermal stress -- a

MAR region. No increase in mortality

key cause of coral bleaching -- at 24 reef sites around

the world, including Glover's Reef Atoll in Belize.

percentages associated with bleaching

events.

This web-based system, developed by NOAA Coral Reef

Watch, uses satellite data to estimate sea surface

TA R G E T

temperature and other bleaching-related indices56.

Reduction in the frequency of NOAA

The program includes a system for generating

Bleaching Watches issued for the

bleaching alerts that enable real-time monitoring of

MAR region. Reduction of subsequent

bleaching events. Given the projections for increasing

mortality associated with these events.

ocean temperatures and coral bleaching events,

Protection of naturally resistant or

this is one of the most important indicators of global

resilient areas.

resilient

climate change (GCC) for coral reefs.

Why Do We Measure It?

RED FL AG

Increase

Increase in the frequency of NOAA

Coral bleaching can be attributed to many causes.

Bleaching Watches issued for the MAR

However, in recent decades a correlation between

region.

elevated sea surface temperatures (a key impact

of global climate change) and the occurrence of

widespread bleaching events has become evident.

With improved understanding of bleaching thresholds

· Degree Heating Week (DHW) - an indication of the

and satellite technology, it is now possible to predict

thermal stress experienced over the preceding 12-

bleaching events on a global scale by studying the

week period (a measure of the duration and strength

changing patterns of sea surface temperature. This

of thermal stress).

Coral Bleaching Index warns managers of imminent

bleaching events and allows them to initiate monitoring

For methodological details, see the NOAA Tropical

even before bleaching actually begins.

Ocean Coral Bleaching Indices webpage56: http://

coralreefwatch.noaa.gov/satellite.

Although local managers can do little to prevent

bleaching events, monitoring their occurrences is

particularly useful in identifying highly susceptible

areas, as well as areas resilient to thermal stress (see

D15 Reef Resiliency to Bleaching for definitions).

NOAA defines five status levels of thermal stress:

Appropriate management actions can then be

initiated such as reef restoration or protection from

Stress Level

Variable Definition Interpretation

localized human-induced stresses that can lower reef

No Stress

HotSpot < 0

No Thermal Stress

resistance to bleaching.

Bleaching Watch

0 < HotSpot < 1

Low-Level Thermal Stress

How Do

How Do We Measure It?

1 < HotSpot and

Thermal Stress is

Bleaching Warning

0 < DHW < 4

Accumulating

The Coral Bleaching Index is a function of three key

variables:

1 < HotSpot and

Bleaching Expected

Bleaching Alert Level 1

4 < DHW < 8

· Sea surface temperature (SST),

1 < HotSpot and

Significant Bleaching

Bleaching Alert Level 2

· HotSpot the difference between SST and the

8 < DHW

Expected

climatological maximum monthly mean temperature

Data Source56

(a measure of thermal stress intensity), and

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