This record provides an overview of the NESP Marine and Coastal Hub Research Plan 2023 project "Improving data on the distribution and ecological value of temperate subtidal seagrass in tayaritja (Furneaux Group of Islands), Tasmania". For specific data outputs from this project, please see child records associated with this metadata. -------------------- Seagrass meadows are a dominant marine ecosystem of tayaritja (Furneaux group of Islands) in the north-eastern waters off Tasmania, with historical coarse mapping indicating extensive beds of Posidonia, Amphibolis, Hetreozostera and Zostera seagrass. The beds of Posidonia and Amphibiolis are potentially some of the largest and deepest extents found in temperate waters of Australia. Lack of data on the distribution and ecological value of these seagrass habitats represents a significant knowledge gap in understanding Australian wetland natural assets that provide a range of ecological, social, cultural and economic values. This project aims to map the extent and ecological composition, population structure and blue carbon value of the seagrass beds around tayaritja in partnership with the Tasmanian Aboriginal Centre. This project will help managers and the Aboriginal communities to understand the significance of these seagrass meadows and understand how they may be monitored. Outputs • Seagrass extent and composition map for Furneaux group [dataset] • Video and imagery of seagrass [dataset] • Final project report [written]

Genomic sampling locations and meadow indices for ribbon weed (Posidonia australis) and wire weed (Amphibolis antarctica) in Shark Bay (Gathaagudu)

Growth (shoot count) of Amphibolis antarctica and Posidonia australis following transplant to Middle Bluff and Dubaut Point, Shark Bay. Plants were transplanted by the Malgana people with assistance from UWA staff then assessed for shoot counts after 8 months.

Assessment of Posidonia australis transplant survival at 3, 8, 12, 18, and 26 months (August transplant); and 3, 8, 12, 18, 26 and 30 months (April transplant), after planting at Middle Bluff, and Dubaut Point, Shark Bay.

Total organic carbon (TOC) sediment stocks as a CO2 mitigation service require exclusion of allochthonous black (BC) and particulate inorganic carbon corrected for water–atmospheric equilibrium (PICeq). For the first time, we address this bias for a temperate salt marsh and a coastal tropical seagrass in BC hotspots that represent two different blue carbon ecosystems of Malaysia and Australia. Seagrass TOC stocks were similar to the salt marshes with soil depths < 1 m (59.3 ± 11.3 and 74.9 ± 18.9 MgC ha-1, CI 95% respectively). Both ecosystems showed larger BC constraints than their pristine counterparts did. However, the seagrass meadows’ mitigation services were largely constrained by both higher BC/TOC and PICeq/TOC fractions (38.0% ± 6.6% and 43.4% ± 5.9%, CI 95%) and salt marshes around a third (22% ± 10.2% and 6.0% ± 3.1% CI 95%). The results provide useful data from underrepresented regions, and, reiterates the need to consider both BC and PIC for more reliable blue carbon mitigation assessments.