Ms Rachel Nicholls1, Dr Kathryn Wiltshire1, Dr Sarah Catalano1, Dr Christopher Bolch1, Dr Danièle Giblot-Ducray2, Dr Kelly Hill2
1SARDI Aquatic and Livestock Sciences, West Beach, Australia, 2SARDI Crop Sciences, Urrbrae, Australia
Biography:
Rachel Nicholls is a Molecular Technologist in the South Australian Research and Development Institute’s (SARDI) Marine Biotechnology Subprogram. Her expertise is in a range of molecular techniques, including next-generation sequencing, real-time PCR, metabarcoding, single-cell isolation, and DNA preparation. She has used these techniques to investigate the diet and microbiome of apex predators, uncover microalgal community dynamics, and monitor key organisms including harmful algae and fisheries species. Her current role focuses on using molecular technologies to better understand the impacts and ecology of harmful algal blooms, and improve monitoring and early detection methods.
Abstract:
Water samples for eDNA analysis were collected from multiple sites offshore and within South Australia’s gulfs during the 2025 – 2026 Harmful Algal Bloom (HAB) event dominated by Karenia species. DNA metabarcoding was carried out targeting the 28S rRNA gene, alongside species-specific qPCR assays for Karenia cristata and Karenia mikimotoi. Both newly-developed and published qPCR assays were laboratory validated and calibrated using environmental and pure culture samples with known cell concentrations to determine the assay limits of detection and capacity for accurate quantification of field samples. The relative performance of metabarcoding and qPCR approaches was compared across a wide range of samples from areas of differing HAB intensity and species composition, and in areas free of HAB taxa. This dataset allows for extensive validation of qPCR and metabarcoding techniques and assesses their utility for monitoring and understanding past and potential future HAB events. The validation approaches applied during this study also provide a framework for assessing other assays and molecular approaches for diverse purposes. In this presentation we will describe the validation framework and key learnings on the utility of different approaches for detection, quantification, and analysis of HAB dynamics.