Seeds For Snapper Seagrass Restoration

Fleurieu Peninsula, SA

OzFish has been leading the restoration of seagrass meadows in South Australia since 2020 and now we’re expanding our program in the state. Until now, we’ve been restoring seagrass only along Adelaide’s metropolitan coastline but now we’ve launched a second SA Seeds for Snapper project on the Fleurieu Peninsula.

This project is trialing methods to rehabilitate degraded seagrass in the waters surrounding the Fleurieu Peninsula. Register your interest for the 2025 Seeds for Snapper season today.

Register to volunteer

Seagrass Collection Guide

A new citizen science initiative has been launched through the iNaturalist platform that you can be a part of.
Get involved by joining below, and if you spot seagrass fruit along the Southern Fleurieu beaches – take a photo and upload it.

Register Now

4050

seeds dispersed

300

volunteers

185

sandbags installed

Seagrass restoration in South Australia has been underway for several years, with the Fleurieu Peninsula site kicking off in 2022.

Expanding seagrass success from elsewhere

OzFish has been successfully delivering its Seeds for Snapper restoration program in South Australia since 2020.

Methods used along Adelaide’s metropolitan coastline are now being trialled at sites around the Fleurieu Peninsula.

Trial sites are monitored to determine which restoration techniques work best in different conditions, such as high wave action.

The importance of seagrass

Significant areas of seagrass meadows have been lost from South Australia’s coastline, causing detrimental impacts to local native fish populations.

As well as providing an important habitat for fish, seagrasses also help to stabilise soil and sediment on the ocean floor, helping to protect Australia’s shorelines from erosion and storms.

Seagrasses also store carbon and nutrients, which helps to improve water quality and clarity – a hectare of seagrass stores 35 times more carbon than a hectare of rainforest.

A helping hand

Seagrass meadows are naturally slow spreaders and struggle in sandy habitats.

That’s why OzFish is giving the environment a helping hand to ensure seagrass seeds get to the right places and have the best chance of taking root and growing.

Each year, in late November to early January, Posidonia seagrass produces a fruiting body that floats to the sea surface.

Although thousands of these fruits are produced each season, many are washed onto the shore by wind and currents – resulting in seed decay.

Collected and processed

To address this challenge, OzFish mobilises beachcombers and boaters to collect the fruit they find – either washed ashore or floating on the ocean’s surface.

Beachcombers collect the fruits and place them in a bucket with some water, while boaters bring the floating fruit in by dipnet – being careful not to catch other marine life by accident.

The fruits are then processed on shore in tanks, and the resulting seeds are sewn into environmentally friendly biodegradable sandbags. These are then placed back in the ocean, at the correct depth, at identified locations.

Keeping your eyes open

The change in winds and currents means that it’s not always known where and when seagrass fruits will wash ashore or be found on the ocean’s surface.

Quite often, they’ll just appear without any prior indication, and that’s why the local community volunteer network is key to the success of seagrass restoration in South Australia.

When you register to be part of this year’s initiative, you’ll find out about how OzFish will spread the word to you and others when seagrass fruits are spotted in the local area.

Many fruits are also swept far out to sea, where when the fruit opens, the seeds sink to the deep ocean floor where sunlight does not reach. Without sufficient light, these seeds also do not grow.

Frequently Asked Questions

Seagrasses are flowering plants that have evolved to live in marine environments. Seagrasses have root systems like land-based plants and that is one of the main ways that they differ from seaweeds or algae which do not have root systems. They grow like urban lawns, sending out runners or rhizomes to cover available space, forming large underwater meadows.

Seagrasses also produce flowers. The male flowers release pollen which fertilizes the female flowers. Once fertilized, the seed and fruit develop. Once mature, the fruit release from the flower head and float to the surface.

Floating fruit tend to be dispersed by the wind and currents until they split open, releasing the seed, which then sinks to the seafloor where it puts down roots. Research has shown that seeds are potentially an effective way of restoring many Australian seagrasses because we can collect large amounts efficiently, which can then be used to restore large areas.

Sometimes called ‘Strap-weed’ or ‘Ribbon-weed’, Posidonia spp. are multiple species of seagrass that have long, blade-like leaves and can grow up to 1m in length, but typically around 30-60 cm.

Along South Australia’s coast, there are at least four different types of Posidonia, including Posidonia australis, Posidonia sinuosa, Posidonia angustifolia, and Posidonia coriacea which naturally form mixed-species meadows.

Posidonia forms a dense canopy that is important for sheltering many marine animals, particularly juvenile snapper, King George whiting and blue swimmer crabs.

Posidonia also plays host to a diverse range of small organisms called epiphytes (plants) and epifauna (animals) living in microhabitats and grazing on the leaves, stems and root systems.

These organisms are in themselves important contributors to the overall productivity of seagrass meadows and, due to their rapid growth, can be useful indicators of the nutrient loading in the water column. Even in a decomposing state, seagrass leaf litter (now known as detritus or wrack) comprises the main diet for many marine species.

Posidonia can form large, dense stands (called meadows), and is also often found with other seagrasses, macroalgae and razorfish. The expansion of Posidonia meadows occurs primarily by the lateral (sideways) growth of the rhizomes. Sexual reproduction is via the production of flowers (male and female reproductive organs on the same plant) that are pollinated underwater.

Most Posidonia species in SA fruit from November to January, and the floating fruits are distributed by currents before splitting open to expose the seed.

A healthy fruit that has a seed inside is green/yellow in colour, and 1.5-2 centimetres in length. A fruit that has recently split open is still green/yellow and looks like a banana peel.

An old fruit that has split open will turn brown after 1-2 days in the sun.

Ideally, we want you to target fruit that is still intact (green/yellow and unsplit) and with the seed still inside.

If you have intact fruit mixed with a small amount of split fruit that is fine, there is no need to sort through it but please ensure the majority of your catch is not split fruit. If we collect too many fruit husks we risk having lots of fruit material but no seeds and this can be very time consuming to separate.

We would ideally like you to sort it and provide us with mainly fruit with seeds intact, but please limit your handling of the intact fruit.

Check our collection guide

Drop off locations, dates and times will be announced closer to the start of the Seeds for Snapper season.

Please also register as a Seeds for Snapper – Fleurieu volunteer.

Register Now

Listen to Project Scientific Leader Associate Professor Jason Tanner from SARDI Aquatic Sciences on his research in connection to this project.

Listen to Jason Tanner’s OzCast episode