Effects of persistent thermal plumes on Zostera muelleri reproductive effort, seed bank densities and seed bank viability

A warming climate poses significant threats to seagrass species worldwide, resulting in ecosystem impacts such as reduced foreshore stabilisation, decreased fisheries habitat, and diminished carbon sequestration. The recovery of seagrass is often inconsistent, taking weeks to years, and in severe cases, recovery may not occur. Recovery is facilitated through both asexual and sexual reproduction, with smaller or short-term disturbances typically favoring asexual reproduction, while large-scale disturbances rely on a persistent seed bank. This study investigated reproductive metrics of Zostera muelleri in persistent thermal plumes, measuring reproductive shoot density, spathe counts, and seed bank density and viability. An estuary affected by thermal effluent, Lake Macquarie, NSW, Australia, was used as a proxy for future climate scenarios and compared with two other east coast Australian estuaries. Seed banks in all three systems were relatively small (averaging 16 seeds m⁻²), suggesting that these populations may not rely strongly on seed banks for recovery. Mean reproductive shoot densities ranged from 4 to 8 shoots m⁻², while spathe counts averaged between 10 and 20 per reproductive shoot, with peak reproductive metrics observed in November and January. Importantly, no significant differences in reproductive shoot densities, spathe counts, or seed bank viability were found between thermally affected (mean maximum temperatures ~2 °C higher) and ambient conditions, indicating that Zostera muelleri reproduction on the east coast of Australia may have the capacity to acclimate to temperatures expected by the end of the 21st century.

Marine Pollution Bulletin

Marine Pollution Bulletin

222

1879-3363

N/A

N/A

11