Coral heat stress

Bleaching risk for Grenada's reefs.

Sample content — not an operational product

The coral heat-stress level is not yet published from the GMS forecast system. The figures on this page are illustrative and must not be used for any weather, marine or safety decision.

Heat stress levels

Based on degree heating weeks (DHW): how much, and for how long, the sea has been hotter than the reef can tolerate
Level	Heat stress	What it means for coral
No stress	None	Normal conditions
Watch	Low	Sea warming towards the stress threshold
Warning	Building	Stress is accumulating; bleaching possible
Alert level 1	4 DHW or more	Significant bleaching likely
Alert level 2	8 DHW or more	Severe, widespread bleaching and some coral death likely

What bleaching is

Corals live with tiny algae in their tissue that give them food and colour. When the water stays too warm for too long, corals expel the algae and turn white. Bleached coral is not dead, but it is starving; if the heat lasts, it can die.

Healthy reefs protect Grenada's coast from waves and support fisheries and tourism, so heat stress on the reefs matters to everyone.