UQ research proves deep-reef coral hates the light, prefers the shade

Deep-reef coral grows more prosperously in very little sunlight researchers at The University of Queensland and the ARC Centre of Excellence for Coral Reef Studies have found.

The research team looked at coral populations from three habitats on coral reefs – the sheltered back reef (Back Reef), the wave-exposed top of the reef slope (Upper Slope) and the dimly lit deeps (Deep Slope).

There is little gene flow between the coral populations at each depth and the algal endosymbionts, which provide energy for the corals to survive, are genetically different across habitats.

The new research, published in BioMed Central's open access journal BMC Evolutionary Biology, used genetic and photosynthetic analyses to demonstrate that these genetic differences reflect adaptations to the different environmental conditions encountered at different depths.

Dr Pim Bongaerts from UQ's School of Biological Sciences said the coral in the Deep Slope habitat was found to be far more abundant and grew faster, despite only receiving a small amount of light available in shallow habitats.

“While normally corals are dependent on light for their energy requirements, the deep corals appeared to have adapted to low-light conditions by having an increased capacity to exploit nutrients and plankton,” he said.

“The different selective pressures across reef environments pose an ecological barrier to migration and further promote genetic divergence of these coral populations by limiting the extent of interbreeding.

“This case study clearly shows how ecological processes of selection can play an important role in the diversification of corals.”

Transplantation of coral fragments to different habitats did not alter the algae-host symbiosis.

Source: University of Queensland