Nature Notes: The Seagrass Meadows of the Geraldton Coast

The first time you wade into Geraldton’s water with a mask on, you realise the coastline has two worlds: the one we move through on land, and the quieter, green-lit world just beneath the surface.

That second world belongs to the seagrass.

Offshore from Bluff Point and Sunset Beach, meadows of Posidonia and Amphibolis stretch across the shallow seafloor - not forests, exactly, but something close.DBCA’s marine habitat maps list these meadows as some of the most important ecological structures along WA’s coast. Not algae. Not seaweed.True flowering plants.

Rooted. Rhizomed. Breathing underwater.

Posidonia australis builds the broad, strap-like leaves that move in slow arcs, like fields of wheat bending to invisible weather. Amphibolis antarctica, the wireweed seagrass, grows stiffer branches tipped with delicate leaf clusters, each one a small nursery for invertebrates and fry.

Together, they hold the coastline in place.

This afternoon, drifting over the reef edge at Bluff Point, the sun cut silver lines through the water. The meadow swayed, gentle but steady, as if exhaling. Schools of juvenile fish darted above the blades - tiny whiting, hardy gobies, small herring no longer than a finger.

In Shark Bay, you see how vast seagrass can be.

Here, you see how essential it is.

Every blade is a small act of shelter.

Every clump is a nursery.

Seagrass slows the water just enough for sediment to settle. It oxygenates. It stabilises the seabed. And, less visibly but just as importantly, it locks away carbon - blue carbon - at rates that dwarf most terrestrial forests.

The roots store decades, even centuries, of sequestered carbon in layers the eye never sees.

Geraldton’s meadows have no fanfare. They don’t ask for attention. But their health is a quiet indicator of the coast’s stability.

When the water is clear, when the rhizomes hold fast, when fish flicker above the leaves - the system is working.

When seagrass thins, or tears away in storms, or clouds with sediment - the coast begins to fray.

I floated above the meadow for a long time today, watching the tide tug gently at the leaves. A single blue swimmer crab scuttled beneath the cover, leaving a faint trail in the sand. A ray lifted slowly from its resting hollow, sending up a puff of silt like a soft breath.

Everything here moves in gradients - light, tide, shadow, season.

And yet the meadows endure, piece by piece, blade by blade.

In the quiet green light, it’s easy to forget the noise of the land.

Down here, the work of holding the coast together continues without witness - slow, ancient, and utterly essential.