How to become a
Storm Squad Member

The Posidonia australis fragments that you will be collecting will be used as donor shoots in the restoration.
To be able to be replanted, the fragments you collect must be healthy, living and with still some rhizome
(the “trunk”-like part at the bottom of the shoot where energy for growth is stored).

Not sure what this means?

Don’t worry, we’ll show you what you need to know!

Posidonia australis – what does it look like?

Healthy, living Posidonia australis is vibrant green, with long, wide leaves growing straight upward from a woody base that runs flat along the seafloor – the rhizome. These are just like the long, horizontal runners found on strawberry plants.  There may be multiple shoots coming from a single rhizome, and often you will see several white roots attached as well.

The growing region of the plant, which we call the meristem, is at the base of the green leaves, and looks slightly pink, especially in the inner leaves.

When it is washed ashore, it looks:

·       Bright, vivid green, sometimes a little brown on the tip

·       1-1.5cm wide leaves (about one finger width)

·       Long leaves, usually between 10cm-40cm

Figure 1.  Detailed illustration of  Posidonia Australis    Source:  James Cook University

Figure 1. Detailed illustration of Posidonia Australis
James Cook University


Rhizome or no rhizome?


We can only replant Posidonia that has an intact rhizome.

Pics showing rhizome and close up.

Pics showing rhizome and close up.


The rhizome is the underground stem, with green leafy shoots growing vertically upwards at 1-3 cm intervals along the rhizome.
The rhizome looks brown and woody and is usually quite stiff.
If the leaves are not attached to a rhizome, at least 1-2cm long, then you should leave it on the beach.

Dead or alive?

When Posidonia australis dies, it loses the vivid green colour and turns a muddy brown.
We cannot replant dead Posidonia so it’s best to leave it on the beach.

The picture on the left shows green seagrass = ALIVE (Yes, pick it up!) The picture on the right shows brown seagrasses = DEAD (leave)

The picture on the left shows green seagrass = ALIVE (Yes, pick it up!) The picture on the right shows brown seagrasses = DEAD (leave)


Posidonia or Zostera?

When collecting Posidonia fragments it is important to ensure you are collecting the correct species.

Posidonia and Zostera are two seagrasses that can be found in the waters around Port Stephens. They look very similar when washed ashore and can easily be confused!
There are a few key differences in telling the difference between the two.


Zostera – Eelgrass or Ribbonweed (left)

Olive green/yellow/brown leaves

Soft, flexible leaves

Narrow leaf (0.1cm-0.5cm wide)

Shorter leaf (1cm-50cm)

Leaves in bundles of 4-6

Leaf tip rounded

Slender rhizome

Posidonia – Strapweed or Broadweed (right)

Bright green leaves

Thick, stiff, strap-like leaves

Wide leaf (1cm-1.5cm – a fingers width)

Long leaf (30cm-60cm)

Leaves in bundles of 1-4

Leaf tip square/ragged

Thick, woody rhizome


With wide, long leaves, Posidonia australis has the largest leaves of any seagrass in NSW. In comparison, Zostera leaves are far narrower, shorter and more flexible.

The easiest way to tell the difference between the two species is based on size. Are the leaves long, bright green and about as wide as a finger? Then congratulations, you have found Posidonia! If the leaves are narrow, in bundles, and the plant is small then you may have found Zostera – keep looking!

Collection permits

The NSW Department of Primary Industries allows persons to remove up to 20 kg/ day of seagrass ‘wrack’ from beaches or the intertidal zone for personal use without a permit.

As this restoration is also part of a research project, we are also operating under Scientific Collection Permit P17/0070-1.0, which in accordance with the Fisheries Management Act 1994 allows the permit holder (Associate Professor Adriana Vergés) and additional people (i.e. volunteers/ citizen scientists) to collect detached seagrass shoots from beaches around the Port Stephens area.

It is a requirement of the Permit that the Marine Park Manager and District Fisheries Officer (DFO) in the area is notified at least 72 hours prior to commencement of any collecting activities. If you are interested in helping us out, please send an email to the following address:, indicating your rough plans for collection.

When is best to go storm squadding?

Time of day

It is best to time your collection just after a morning high tide starts to recede, leaving the strands of broken Posidonia washed up on the beach. A good strategy to maximise the amount of living Posidonia you collect is to walk along the strand line (the line where most of the seagrass is washed ashore) when the tide is coming down, and back along the water's edge on the way back to your car.

Weather Conditions

Posidonia australis anchors itself to the bottom using sturdy roots but can be uprooted by currents or large swells.

The best times to comb the beach for fresh Posidonia fragments are just after events that may cause rough coastal conditions, such as:

  • Storms

  • East Coast Lows

  • At low tide after very windy days

  • When strong Southerlies blow

  • At low tide during spring tides (new moon and full moon)

The absolute best time to search for Posidonia is when a strong wind has been blowing at low tide, especially during spring tides.

Where is best to collect Posidonia australis?

Depending on the weather, there are a few different places that you may expect to find Posidonia washed ashore. The dominant strong winds in Port Stephens are sea breezes – easterlies in the afternoon and westerlies at night.

When a strong easterly blows at low tide, you can expect to find Posidonia washed up along the eastern facing side of bays and beaches, including:

  • the eastern side of Soldiers Point

  • Salamander Bay

  • Pindimar South

  • Upper Pindimar (facing east)

The opposite is true for a strong westerly – when these winds prevail at low tide, go looking for Posidonia on the west-facing beaches around Port Stephens. These include

  • western Soldiers Point

  • eastern side of Salamander Bay

Southerly winds are also very strong, and usually associated with East Coast Lows (also known as East Coast cyclones) and storm systems. As they are generally the strongest winds, they create larger waves and currents and result in plenty of detached Posidonia.

Beaches with a southerly aspect are likely to be good locations for collection when these southerly “busters” come through. Go looking at:

  • Pindimar

  • Jimmy’s Beach

Pindimar is near many dense Posidonia meadows and will often have fragments washed ashore after any strong wind.

Do I need to bring anything when I go out to collect?

Yes! It’s a good idea to bring several things:

  • A damp bag/container to carry collected fragments

  • A bucket in the car to put your fragment bag in

  • Sun protection (hat, sunscreen, sunglasses)

A good bag option for collecting is a pale coloured plastic or a wet canvas bag, which prevents the Posidonia from the heat and stops it from drying out.

 Optional things to bring:                                                                                                                              

  • A second bag to collect any plastic debris or rubbish you may find

What do I do with the collected Posidonia?

You can drop off your collected fragments to the Anchorage Marina - the collection area is best entered along the eastern boardwalk from Corlette Beach. If you have time to provide some data just follow the instructions in the datasheets near the collection station. If you don’t have time, that’s perfectly fine! Any healthy fragments will help us in our restoration efforts.


There are many things that also wash up on beach that may sting, bite or cut, so it is a good idea to be aware of this when beachcombing. Most of these hazards can be managed by using common sense!

When collecting, please look but do not touch:

  • Jellyfish

  • Blue bottles (these can still sting after death!)

  • Fish – these often have sharp spines that can inflict a nasty cut

  • Blue ring octopus

  • Sharps (broken glass etc)

    Please leave in the beach any Posidonia shoots that are not suitable for restoration (too brown/ too dry/ no rhizome). This forms important biomass when it gets swept back into the ocean.

Happy storm squadding!

Thank you for helping us restore Posidonia australis in our beautiful blue backyard.