BIODIVERSITY

Corals are doin’ it by the full moon

With all the doom and gloom this year about the Great Barrier Reef suffering massive back-to-back bleaching events, you’d be right to feel a bit depressed about the future of this amazing and unique ecosystem. But Australia’s marine biologists aren’t taking these setbacks lying down.

At the Australian Institute for Marine Science, biologists are using the everexpanding National Sea Simulator near Townsville, to conduct experiments on coral reproduction and resilience.

Why now? Because in November and December this year, during the full moons of those months, many corals on the reef will “spawn”, and release billions of packages of eggs and sperm into the warmer summer waters.

There this genetic material will mix, combine, and grow into billions of coral larvae. These microscopic creatures will – if conditions are favourable – each find a tiny space on the reef and begin the slow but inexorable process of building a calcium-carbonate skeleton.

In perfect, pre-industrial conditions, the great spawns would see the reef expand to the very limits of what dominant currents and ocean temperatures allow. Corals are surprisingly tough – if given certain guarantees. And chief among these is water temperature.

Too hot, and corals will respond by “dumping” their symbiotic zooxanthellae algae, which turns the coral colonies white. This is what we call bleaching.

By collecting eggs and sperm and growing the corals – particularly the species pictured, A. millepora – in the National Sea Simulator, scientists like Dr Line Bay (pictured) hope to discover which corals are the most tolerant of changing conditions.

And perhaps even more importantly, which corals can actually withstand expected ocean warming, and how understanding their ability might give us a chance to save the reef.