13/02/2026
These photos are from a five day research trip on Wavelength to Opal Reef that finished earlier this week. The trip was led by Dr Rachel Alderdice from University of Konstanz with other researchers from UTS and Coral Nurture Program (Paige, Christine and Hadley).
Read on if you are interested in the research .....
Rachel is studying how chromoproteins influence thermal tolerance in coral. This trip involved testing different colour morphs of the same few species. The tests run overnight, with samples collected and frozen in liquid nitrogen for later analysis. There was also photogrammetry, spectral analysis and other sample collection. The main tests are CBASS (Coral Bleaching Automated Stress System) which have samples exposed to different temperature and light regimes for a set time and the impact on photosynthetic efficiency measured with Pulse Amplitude Modulation Fluorometry (known as PAM'ing). We have had CBASS tests on Wavelength for about six years and Rachel's set-up was the neatest, most efficient system so far.
Chromoproteins are one of four groups of proteins that give coral most of their colour. The others are the photosynthetic pigments, fluorescent pigments and kindling proteins (which can switch between fluorescent and non-fluorescent). They can be made by the coral host itself and are thought to have a photoprotective role.
When you go snorkelling don't be surprised that the most common colour of coral is golden-brown. Often, shallow healthy coral has lots of symbiotic algae and the photosynthetic pigments absorb red and blue wavelengths of light and reflect some orange and yellow. This, therefore, gives most healthy shallow coral a brownish colour. But, it is also normal to see other colours such as blues, yellows and pinks, with the same species of coral often being present in different colours nearby each other. Most often colonies retain the same colour except for extreme conditions, but in aquariums it is common to use nutrients, feeding, and lighting to reduce the symbiotic algae and boost the colourful pigments. When combined with special lighting, this makes the corals look incredibly bright and colourful.
Fluorescent pigments are the best studied and have antioxidant and photoprotective roles, but non-fluorescent pigments are not so well understood. They likely have a photoprotective role but possibly other roles such helping provide a chemical "invitation" to certain symbiotic algae. There are still many questions, such as how they are regulated and how much of a contribution they make to thermal tolerance, how exactly do they do that, and how the different pigments work together. Even the most basic aspects of coral bleaching are still being unravelled, such as how much bleaching resistance can be attributed to the symbiotic algae, the other parts of the holobiont, or the coral host itself, and this type of study helps understand that.
We love helping with this sort of research as it contributes to foundational coral knowledge, helps understand coral adaptation to warming surface waters and has relevance to assisted recovery techniques. Ongoing monitoring at the site as part of site stewardship can also help understand the pigment role ... for example, when (or if) do the colours change, what is the relative abundance of colour morphs, might the relative abundance of change over time?
photos and text by John Edmondson
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