Restoring Sydney Harbour’s seagrass

So our native seagrass (Posidonia australis) here is possibly found only Australia. It's a really slow growing plant. Seagrass is a plant - it fruits and it flowers. But Seagrass has also been dramatically impacted by our urbanisation - things like runoff into the harbour, but also physical destruction of seagrass. Things like boat moorings. Swing moorings are like big lawnmowers for seagrass, if you look at underwater photos of the harbour seabed, you see mooring scars, and once you've lost that seagrass environment, it doesn't come back without direct intervention.

What you find in those seagrasses is all kinds of sea-life. It is a really common area for fish to not only spawn in, but for smaller species to live in - because they're protected, they've got shelter there. We have two species of seahorse in Sydney Harbour. There is a Pot-Bellied Seahorse (Hippocampus abdominalis), which is a larger species, and there is the White's Seahorse (Hippocampus whitei), which is a much smaller species. But seahorses, are really bad swimmers! In fact, it is not only one of the Australian species, but one of the worldwide species recognised as the slowest swimmer in the world, and they really don't have great mechanisms to transport themselves in the ocean.

They've got these prehensile tails which can grab onto things, and that's how they live their lives - held on to something, and feeding all the time. Seagrasses are really natural anchor points for a seahorse, and because we've lost so much of that environment, the White Seahorse is one of only two seahorse species globally, which is recognised as being endangered. In Sydney Harbour, that's primarily through urbanisation and loss of habitat, and one of those key habitats is our native seagrasses.

The research project is called Operation Posidonia. While it is a scientific program, it is really great because it has a strong community outreach component to it. Because we've had such loss of seagrass in Sydney Harbour, we find that we have to translocate seagrasses from both Broken Bay in the north and Pork Hacking to the south. What tends to happen in seagrasses in Eastern Australia, you have large storm events, it uproots them, they're disturbed, they wash up on the beach. The team works with local community groups who collect. So we've got this research group who are doing this amazing work with seagrasses, this huge community outreach component where seagrasses get dislodged after storm events.

In fact, they call the community engagement part the storm squad. Quite often, they're local ocean swimming groups, for example, and they go and collect the seagrass that's viable. We bring it back to places like our outdoor aquarium here at the Sydney Institute of Marine Science. We nurture it for a period of time, and then we're able to go and replant it in replanting exercises where we put mats down, we're able to monitor it, we can measure the growth rates, we can measure the expansion beyond where we originally planted it, because obviously the idea isn't just to go and keep planting it, it's hopefully become self-sustaining and it starts to spread on its own.