Dr Aimee Van Der Reis1, Professor Mary Sewell1, Professor Wendy Nelson2
1University Of Auckland, Auckland, Aotearoa / New Zealand, 2Auckland War Memorial Museum Tāmaki Paenga Hira, Auckland, New Zealand
Biography:
Aimee van der Reis is a postdoctoral fellow based at the University of Auckland. Aimee's interests lie in using modern molecular techniques to unpack complex questions typically associated with the marine environment. She is particularly interested in using DNA metabarcoding for conservation and management purposes.
Abstract:
Crustose coralline algae (CCA) are slow-growing, long-lived, rock-like red algae with calcium carbonate cell walls. As ecosystem engineers, CCA cover an estimated 52.5% of coastal reef surfaces worldwide. Recent research has demonstrated their capacity to function as biological “seed banks”, harbouring dormant stages of macro- and microalgae within rhodoliths, the nodose growth form of CCA. This discovery suggests that CCA may play an underappreciated role in the recovery of marine ecosystems following disturbances such as marine heatwaves. Whether the more ecologically dominant encrusting CCA also functions as a marine seed bank remains unknown.
To begin investigating this, we explored the biodiversity within encrusting CCA using DNA metabarcoding. Ninety-six encrusting CCA samples were collected from Karitane (New Zealand) across four depths. A wide range of biodiversity was identified using four gene regions, and although taxonomic assignments were hindered by the limited availability of algal DNA reference sequences, targeting multiple gene regions partially compensated for this limitation. The dominant non-calcifying macroalgal species detected are known to possess heteromorphic life histories, consistent with the possible presence of dormant life stages within encrusting CCA. The CCA sequences themselves revealed remarkable diversity, with population-level resolution possible, indicating undescribed flora within a small geographic area. Together, encrusting CCA identity and collection depth explained more variation in the detected community than either factor alone. These findings highlight the need for continued research into the resilience of CCA and their potential role as a seed bank in facilitating the recovery of marine communities following disturbance.