Dr Anjali Gopakumar1,2, Dr Laura Airoldi3,4, Dr William Glamore5, Dr Paul Gribben6, Dr Ana B. Bugnot7, Dr Katherine A. Dafforn1,8
1School of Natural Sciences, Macquarie University, Sydney, North Ryde, Australia, 2Department of Biological, Geological, and Environmental Sciences, University of Bologna , Ravenna – 48123, Italy, 3Chioggia Hydrobiological Station “Umberto D’Ancona”, Department of Biology, University of Padova, Uo CoNISMa, Chioggia – 30015, Italy, 4NBFC, National Biodiversity Future Center, Palermo – 90133, Italy, 5Water Research Laboratory, University of New South Wales, Sydney, Australia, 6Centre for Marine Science and Innovation, School of Biological, Earth and Environmental Science, University of New South Wales, Sydney, Australia, 7CSIRO Environment, Commonwealth Scientific and Industrial Research Organisation, St Lucia, Australia, 8School for the Environment, University of Massachusetts , Boston, USA
Biography:
Anjali Gopakumar is a postdoctoral researcher at Macquarie University, Sydney where she is investigating the impacts and management of the invasive ascidian, Didemnum vexillum in Australian waters. She completed her PhD in 2024, where she assessed the restoration responses of lesser-known ecosystem function and service indicators such as microbial communities and biogeochemical fluxes in coastal salt marshes in the Venice lagoon, Italy and in the estuaries of New South Wales, Australia. Prior to her PhD, Anjali completed her Erasmus Mundus Joint Master degree in Marine Biology (IMBRSea) at Ghent University (Belgium), with a fully funded EMJMD scholarship. She also worked as a Research Assistant at the University of Oslo (Norway) for two months, continuing her Master Thesis studies on mercury accumulation in fish from the Northern Barents Sea in the Arctic.
Abstract:
Sediment microbes play important roles in salt marsh ecosystems by mediating biogeochemical cycling. While tidal restoration aims to reinstate tidal flushing and vegetation in degraded salt marshes, its effects on sediment microbes and biogeochemical processes remain poorly understood. We compared sediment fluxes of hydrogen sulphide (H2S) and nitrous oxide (N2O), bacterial diversity, community structure and predicted nitrogen/sulphur (N/S) cycling pathways across seven restored salt marshes and between vegetation states (vegetated and unvegetated) in the Hunter River estuary, Australia. Salt marshes differed in restoration approach and age (1990-2017). We hypothesised that vegetated sediments would support greater bacterial diversity and biogeochemical cycling, and that restored sites would show similarities due to similar tidal regimes. Sediment samples were collected and bacterial communities were characterised using environmental DNA metabarcoding of the 16S rRNA gene, and predicted N/S cycling pathways were inferred using PICRUSt2. Sediment H₂S and N₂O fluxes were measured using microsensors.
Vegetated sediments consistently had higher bacterial richness and diversity than unvegetated sediments in all salt marshes, highlighting a clear effect of vegetation on bacterial diversity. However, bacterial community structure and predicted N/S cycling pathways differed between vegetation states only in some marshes, indicating strong site-specific variations. Measured fluxes of H₂S and N₂O did not differ between vegetation states. These findings suggest that while vegetation consistently enhances bacterial diversity, its effects on community structure and biogeochemical functioning are site dependent. This highlights the importance of restoration history, hydrology and local environmental conditions in shaping microbial recovery and ecosystem processes in restored salt marshes.