Summer of seagrass for Fleurieu waters

News article |

You often see it washed up on the beach – long strands of green ocean plant life, strewn among the many other pieces of natural marine debris that have captured our fascination for so long.

Seagrass, or seaweed as it’s often known, is a vital element of marine ecosystems. Underwater seagrass meadows provide several environmental benefits such as protecting our shorelines from erosion and storms by stabilising sand, improving water quality by reducing nutrients and turbidity. Seagrasses play a significant role in global carbon and nutrient cycles. The carbon storage capacity of coastal ecosystems can increase over time, with seagrasses storing up to two to four times more carbon per hectare per annum than terrestrial rainforests and if left undisturbed, can store carbon in their sediment for over hundreds or thousands of years.

Seagrass meadows are also important foraging and nursery grounds for recreational and commercial fish species including baby pink snapper, whiting, blue swimmer crabs, prawns, King George whiting, garfish and squid. They are also critical habitat for many other fish and invertebrate species including the region’s iconic leafy and weedy seadragons.

Throughout many parts of the world, including the coastlines of the Fleurieu, concern has been growing about seagrass diminishing for many decades. Causes can be attributed to land-based impacts including pollution, stormwater discharge and development adjoining coastal areas, as well as rising sea temperatures and storm surges.

To help mitigate and reverse these losses, Landscapes Hills and Fleurieu and local partners are supporting OzFish Unlimited’s national seagrass restoration program, Seeds for Snapper.

It’s the second summer of action on the Fleurieu, where local volunteers are called upon to comb the beaches and near shore waters for seagrass fruit. Fishers are also welcome to participate and collect the floating fruit from marine currents along the coast. Collected fruit (that carry and protect a single seed) will be stored in holding tanks, before literally being propagated into sandbags and returned to the sea floor of Encounter Bay, aiming to reproduce and create boundless underwater meadows of seagrass. The method is a scientifically proven method of seagrass restoration following successful programs in metro waters.

Summer of seagrass for Fleurieu waters
Posidonia fruit collection, Seeds for Snapper volunteer - Sarah Beara

Tape weed (or Poisidonia spp.) seagrass fruits are released sometime between mid-December to January by local seagrass populations that form slicks on the surface of the water and drift ashore on incoming tides.

Landscapes Hills and Fleurieu’s Coast and Marine Project Officer Caroline Taylor explained more.

“We had many volunteers help with seagrass fruit collection last year which enabled us to deploy 150 sandbags (with almost 4000 seeds) to the Encounter Bay seafloor. To ensure local provenance and genetic stability, fruit can be collected along beaches from the Bluff at Encounter Bay to the Murray Mouth at Goolwa. Our holding tanks are at the Encounter Bay boat ramp and can be dropped off 24/7.

Summer of seagrass for Fleurieu waters
Beachcombing for fruits - OzFish Unlimited

“We’re seeing the fruit wash up in WA and other parts of the SA coast which is a sign that we are not far away from seeing them on our beaches. Anyone interested in receiving alerts and being part of the action is encouraged to sign up via the Seeds for Snapper page on the Landscapes Hills and Fleurieu website or at ozfish.org.au,” she said.

Summer of seagrass for Fleurieu waters
Seagrass seed bags being deployed - Michael Sierp

Further to the many benefits the seagrass restoration will provide to the local marine environment, the preservation of a famous shipwreck will also be supported.

“It’s early days, but we are also very excited to be working with the Department for Environment and Water and Flinders University this summer to deploy some of the seagrass sandbags around the well-known South Australia shipwreck at Yilki.

“Shipwreck preservation is obviously a very sensitive and scientific task, but establishing seagrass communities around the wreck will certainly help contribute to its preservation and protection from storm surges and exposure to destructive marine organisms,” Caroline said.

A former passenger vessel and offshore whaling platform, the South Australian wrecked in 1837 and had remained undisturbed and undiscovered on the seafloor at Yilki ever since. In April 2018, a collaborative research program between the Department for Environment and Water and several partners found the remains of South Australian.

Summer of seagrass for Fleurieu waters
Photogrammetry recording of the wreck - Hiroshi Ishii, Flinders University

The ‘Seeds for Snapper’ project is part of OzFish Unlimited’s national seagrass restoration program, funded on the Fleurieu Peninsula by Landscapes Hills and Fleurieu and BCF with support from Department for Environment and Water, Flinders University, SARDI Aquatic Sciences, local councils and community volunteers.

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