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A 9,000-year marine diatom assemblage reconstruction off Eastern Tasmania, Australia, using microfossil and molecular methods

Created 28/09/2025

Updated 28/09/2025

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Over the past fifty years, Eastern Tasmanian waters have experienced rapid warming, primarily due to the extension of the East Australian Current. This has driven expansion of warm-water biota and decline of those adapted to cooler conditions, including phytoplankton. Presently, plankton monitoring, including diatoms along Eastern Tasmania, spans <100 years. This study reconstructed diatom communities throughout a sediment core spanning 9,000 years before present (9 kyrs BP), using microfossil analysis and molecular techniques, including sedimentary ancient DNA (sedaDNA) and NRS 18S rRNA from a 10-year water column archive at the Maria Island IMOS NRS mooring. Microfossil analysis revealed a dominance of strongly silicified benthic taxa (Campylodiscus, Diploneis, Paralia, Pyxidicula, Triceratium). Notably, Paralia sulcata showed a shift ~6 kyrs BP from small to larger cells, possibly reflecting a transition from a coastal to shelf ecosystem. However, microfossils underrepresented lightly silicified planktonic diatoms. Molecular methods detected higher diatom diversity, though up to 50% of sedaDNA reads remained unclassified due to reference library limitations. Lightly silicified planktonic genera (Chaetoceros, Corethron, Lithodesmium, Rhizosolenia) were identified only via molecular approaches and comprised 73% of sedaDNA and 88% of 18S rRNA records. Of 10 shared diatom families, 5, 15, and 4 were unique to microscopy, sedaDNA, and 18S rRNA, respectively. SedaDNA also captured greater benthic diversity. Our findings revealed limitations in reconstructing historic diatom assemblages from sediment cores. Microfossils faced constraints due to difficulties in morphological identification and preservation biases. In contrast, sedaDNA analysis yielded finer taxonomic resolution, provided access to high-quality reference sequence libraries were available.

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Field Value
Title A 9,000-year marine diatom assemblage reconstruction off Eastern Tasmania, Australia, using microfossil and molecular methods
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/e1ce8074-a501-4a5e-93e1-734286d1df98
Contact Point
Australian Ocean Data Network
bradley.paine@utas.edu.au
Reference Period 01/01/2020
Geospatial Coverage
Map data © OpenStreetMap contributors
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Data Portal Australian Oceans Data Network

Data Source

This dataset was originally found on Australian Oceans Data Network "A 9,000-year marine diatom assemblage reconstruction off Eastern Tasmania, Australia, using microfossil and molecular methods". Please visit the source to access the original metadata of the dataset:
https://catalogue.aodn.org.au/geonetwork/srv/eng/csw/dataset/a-9000-year-marine-diatom-assemblage-reconstruction-off-eastern-tasmania-australia-using-microf