High sea surface temperatures were a prerequisite for the development and expansion of the Great Barrier Reef

The Great Barrier Reef is the largest reef system in the modern ocean. To date, the influence of temperature on the origin and long-term evolution of the Great Barrier Reef remains enigmatic. Here, we present a 900-thousand year TEX₈₆^H-derived temperature proxy record from Ocean Drilling Program Site 820 in the Coral Sea. It demonstrates that the onset of reef growth on the outer shelf was preceded by a rise in summer temperature from ~26° to ~28°C at around 700 thousand years ago (marine isotope stage 17). This approximately 2°C rise in summer sea surface temperatures (SSTs) likely resulted in higher carbonate production rates, which were crucial for the formation of the Great Barrier Reef. Subsequently, reconstructed SSTs remained sufficiently warm for the Great Barrier Reef to thrive and evolve continuously. The evolution of the Great Barrier Reef, therefore, appears to be closely linked to SSTs.