Dr Anastasija Zaiko1, Dr Richard Arnold2, Dr Laurin Steidle3, Dr Eric Treml4, Dr Ulla von Ammon3, Dr Xavier Pochon3,5, Dr Michelle Scriver1, Dr Verena Trenkel6, Dr Ross Vennell3,7
1Sequench, Nelson, Aotearoa / New Zealand, 2School of Mathematics and Statistics, Victoria University, Wellington, Aotearoa / New Zealand, 3Cawthron Institute, Nelson, Aotearoa / New Zealand, 4Australian Institute of Marine Science, Perth, Australia, 5Citizens Of The Sea, Nelson, Aotearoa / New Zealand, 6IFREMER, Nantes, France, 7School of Environment, The University of Auckland, Auckland, Aotearoa / New Zealand
Biography:
Dr Anastasija Zaiko is Director and Lead Scientist at Sequench Ltd and President of the Southern eDNA Society. Her work focuses on environmental DNA and RNA applications for biodiversity assessment, biosecurity surveillance, ecological monitoring and environmental decision-support. Her research spans marine, freshwater and terrestrial systems, with particular emphasis on translating complex molecular datasets into outputs that are useful for environmental managers, regulators and industry practitioners.
Abstract:
Marine eDNA assays can detect very small quantities of target DNA, but assay sensitivity alone does not determine whether a rare species will be found. In dynamic coastal environments, eDNA released from sparse populations is transported, diluted, mixed, degraded, and displaced by changing currents, creating patchy and transient signals. A negative sample may therefore reflect failure to intercept the signal rather than true absence.
We used hydrodynamic simulations, Lagrangian particle tracking, and simplified plume models to examine how these processes shape detectability of sessile benthic organisms. The framework links eDNA shedding and decay with current speed, mixing, water depth, tidal reversals, sampling position, and assay detection thresholds.
Results show that eDNA from a single or small group of organisms can form a very narrow detectable plume, often only tens to around one hundred metres wide, even when transported over kilometre scales. Stronger currents do not necessarily improve detection, as increased transport can be offset by greater dilution, while tidal reversals can generate residual plumes that complicate source attribution.
These dynamics have direct implications for sampling design. Increasing filtered volume alone may provide limited benefit if plume encounter probability remains low. Spatially integrated approaches can be more effective: vertical tows reduce variability associated with depth heterogeneity, while horizontal and cross-stream tows increase the likelihood of plume interception. Sampling near the end of ebb or flood tides may further increase detection range.
Marine eDNA surveillance is therefore a problem of signal interception as much as analytical sensitivity.