Corals at Monkey Beach reef off Great Keppel Island were exposed to the air during the spring low tides at around 3am and 3pm on the 28th and 29th of September 2019.

These extreme ‘spring’ low and high tides occur monthly at the time of the New Moon but only the lowest tides of < 0.1m can expose the corals to the air.

Corals can survive exposure as long as it is not for too long or the air isn’t too cold and lunar irradiance is not too high (Anthony and Kerswell, 2013). Images and video courtesy of Max Allen Jnr of Freedom Fast Cats Rosslyn Bay).

Corals exposed at low tide at Monkey Reef on 28 Sept 2019 (© Max Allen Jnr).

At Rosslyn Bay, the low tides (< 0.1m MLLW) occurred at 2:44am and 2:52pm on Saturday 28th September 2019.

At Monkey reef, the early morning spring low tide and the high lunar irradiance may have caused some coral bleaching.

The water temperature was 23 degrees Celcius and air temperatures only slightly lower at 20 degrees Celcius (AIMS weather station at Square Rocks).