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Delivering Tasmania’s first seagrass restoration trial

OzFish, in partnership with the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS), successfully delivered Tasmania’s first Zostera seagrass restoration trial, funded by the Australia Pacific QBE Foundation climate resilience grant.

The trial undertook crucial first steps towards enabling large-scale seagrass restoration in Tasmania, supporting native fish species, a healthy ecosystem, and stronger climate resilience.

22,000 seeds

collected

9000 seeds

deployed

31 volunteers

involved

The project’s findings are paving the way to enabling large-scale seagrass restoration in Tasmania’s Ralphs Bay and returning this vitally important habitat to the region’s waters.

**The importance of Zostera seagrass**

Seagrass meadows are highly diverse and productive habitats that support many coastal fisheries. They also play a significant role in coastal ecology and provide a wealth of other benefits such as habitat provision, sediment stabilisation, and supporting biodiversity.

A hectare of seagrass can store up to 35 times more carbon than a hectare of rainforest so it has a major contribution to make to climate resilience.

Unfortunately, Australia has lost more than 85 per cent of the seagrass around its coastline in recent decades, including in Tasmania.

Many fish species use seagrass meadows as important breeding and feeding grounds, and they act as nurseries for juvenile fish – providing shelter from predators and ocean currents. Lots of invertebrates, crabs and other small fish also like to call seagrass meadows home.

These habitats and its inhabitants play an essential role in marine food webs, with the smaller critters and fish being an important food source for larger fish and popular recreational fishing species including calamari, whiting, garfish, bream, snapper, sea mullet, luderick, and leather jackets.

Developing a greater understanding to support restoration

This OzFish and IMAS trial has helped to develop Zostera restoration approaches and provided critical data that will inform and enable future large-scale seagrass restoration efforts in the region. It is also investigating how sediment nutrient levels can influence seagrass restoration efforts – helping to guide other projects in locations across Australia.

Various restoration techniques

Four restoration techniques were trialled including different ways of distributing seagrass seeds such as seed bags and Direct Injection Seeding (DIS), as well as two methods of transplanting Zostera, using plugs and sprigs. Each of these methods were deployed at 4 different sites in the Derwent Estuary and Ralphs Bay, Tasmania. Recreational fishers have been involved in a number of field days and on-ground activities, including seed collection and a hands-on restoration day.

The restoration methods

Plugs: a PVC pipe is used to collect seagrass with shoots and sediment attached from healthy seagrass meadows. They are then transplanted into recipient sites.

Sprigs: Seagrass from the edge of a healthy meadow is dug up either by hand or using a rake so that shoots, rhizomes (underground stem) and roots are kept intact and divided into small ‘clumps’. Sprigs are transplanted into sections of the seafloor at the recipient sites.

Direct Injection Seeding (DIS): A slurry of local sediment and seeds are mixed and inserted into a calking gun. The gun is modified so that seeds and sediment are dispersed at a predetermined depth and rate of seeds per injection.

Seed Bags: Small hessian bags are filled with local sediments and a predetermined number of seeds. The bags are stitched closed, and a rope is used to attach the bags together, which is pegged to the seafloor to keep them in place.

Regular monitoring

So far, the trial has shown promising results for the chosen methods. In the latest monitoring round in late 2023, Zostera transplants had high survival rates and early signs that the transplants were growing and spreading. Seed bags have begun germinating and their progress will continue to be monitored.

The next steps in the project are to continue the monitoring of the trial sites, to gain a better understanding of which methods have been successful and show long-term potential.

Establishing a restoration legacy

The project’s findings are the first step on the journey to establishing large-scale seagrass restoration in Tasmania and returning this vitally important habitat to the region’s waters. It has provided information on what works and what doesn’t, building on the toolbox of restoration approaches, and allowing future restoration to be more targeted and effective. Overall, the methods showed significant promise for future efforts.

Restoring seagrass meadows is fundamental in improving disaster preparedness, resilience, and recovery for coastal communities.

The research component of the project was led by Kelsie Fractal and Dr Beth Strain, with support from Associate Professors Jeff Wright and Chris Bolch from IMAS, and Professor Paul Gribben, of University of New South Wales.

18 SEPTEMBER 2023 | Innovative Seagrass Restoration Trial Could Deliver Big Wins For Fishing In Hobart

The early signs are promising that a seagrass restoration project in Southern Tasmania will be a major step in the right direction towards replacing lost meadows. In a first for Tasmania, OzFish Unlimited, Australia’s fishing conservation charity, is collaborating with researchers from the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS) to restore seagrass meadows in the southern part of the state.

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6 DECEMBER 2022 | Devil in the detail for Tasmanian seagrass restoration

At OzFish, we’re aware more than most of the importance of seagrass meadows and the extent to which this vital habitat has disappeared from Australia’s coastline. It is estimated that Australia has lost almost 30 per cent of its seagrass meadows since 18801. Tasmania has not escaped unscathed, with much of the state’s seagrass habitats having been lost, fragmented, or damaged. However, the restoration of seagrass in Tasmanian waters is getting underway and we’re proud to be playing a leading role.

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The project is in partnership with the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS). It is funded by the Australia Pacific QBE Foundation and supported by BCF – Boating, Camping, Fishing.

Additional funds were provided through an Australian Research Council Linkage grant awarded to Associate Professor Jeff Wright and Professor Paul Gribben, and a TSSP grant awarded to Dr Beth Strain.