Flora Lam Kim1, Valérie Stiger-Pouvreau2, Xavier Conlan1, Colin Barrow1, Cecilia Biancacci3, Alecia Bellgrove1
1Deakin University, Australia - 2Univ Brest, CNRS, IRD, Ifremer, LEMAR, France - 3Cawthron Institute, New Zealand
Australian cold temperate waters harbour unique algal biodiversity but face significant threats from ocean warming. High solar-UV radiation and intense environmental stresses may drive the production of unique defence molecules in Australian seaweeds. Among these, phlorotannins in brown macroalgae play a crucial role in seaweed defence and exhibit strong antioxidant properties, with applications in food, cosmeceuticals, and pharmaceuticals.
This study compared four endemic Australian fucoid species (Hormosira banksii, Cystophora torulosa, Durvillaea potatorum, and Phyllospora comosa) with North Atlantic counterparts to explore their antioxidant defence strategies. It aimed to: (1) quantify antioxidant activity and phlorotannin concentrations, (2) identify and characterise phlorotannins, (3) assess spatio-temporal variability, and (4) evaluate the effects of temperature and light under controlled conditions.
Results revealed that phlorotannins consistently showed high concentrations and antioxidant activity, with Australian species displaying equal or superior activity to North Atlantic species. Furthermore, molecular composition analysis revealed unique phlorotannins in Australian species. Temporal studies indicated peak concentrations in autumn (H. banksii) and winter (C. torulosa), while spatial study of H. banksii along a 14° latitudinal gradient showed higher concentrations in Tasmania’s colder waters. In controlled experiments, H. banksii exhibited stable phlorotannin production across temperatures (15, 20 and 25°C) and light levels (250, 750 and 1250 µmol photons·m⁻²·s⁻¹), with a significant peak after one week of stress exposure.
In conclusion, Australian brown seaweeds produce high levels of unique phlorotannins, underscoring their potential for commercial applications. This study can help inform both sustainable aquaculture of high-value seaweed-derived compounds and seaweed population management.
Biography
Flora Lam Kim is a PhD candidate in marine biology at Deakin University, Australia, with a strong research background in marine biology, physiology, ecology, and biochemistry. Originally from France, her passion for seaweeds began at the University of Western Brittany (UBO). Flora’s current research focuses on the chemical defence of seaweeds under environmental stress, investigating antioxidant molecules for potential pharmaceutical, cosmeceutical, and food applications.