A gorgeous blue starfish patrols over Acropora and Porites corals caught in the grip of coral bleaching on Australia's Great Barrier Reef.

Heat the ocean, kill the ocean’s great reefs, ripple effects reach inland. It all starts with a simple, well-known phenomenon called coral bleaching, and it’s one that’s been observed occurring all over the world as the climate warms. Most notably, along Australia’s Great Barrier Reef and its lesser-known Southern Reef. And while much of the northeastern US is digging out from an icy, wet March storm, temperatures in the southern hemisphere are hitting their annual highs as summer heat peaks down under:

Mass coral bleaching is occurring on the Great Barrier Reef for the second consecutive year, Australia's lead management agency for the Reef confirmed today. The bleaching is part of a global event affecting the world’s coral reefs over the past two years. Experts from the Great Barrier Reef Marine Park Authority spent six hours yesterday flying over the Reef … The aerial survey, the first for 2017, found severe bleaching in offshore reefs from north of Ingham to the northern extent of the survey near Cairns. This year more bleaching is being observed in this central part of the Reef, which last year escaped widespread severe bleaching.

Not all bleached coral dies, at least not right away, over time, given a chance, some of it can fully recover. But as this becomes an annual event, more and more of the reef’s critical foundation will take repeated hits, the spine and skeleton of the great reef will eventually die and crumble into dust, the structure eroding away, until any recovery on human time scales is impossible.