Seeds of hope for seagrass meadows

Grab your gumboots! Alison Ballance squelches out into Nelson's mudflats with a team of Cawthron Institute researchers in search of cryptic seagrass flowers and their seeds. Collecting the seeds is step one in an ambitious project to restore Aotearoa's ailing seagrass meadows.

Nelson's Haven is an 8-kilometre expanse of mudflats. If you don gumboots and squelch your way out at low tide, you'll find it is also an expansive grassy meadow.

The grass is seagrass, the only flowering plant that lives in the sea. It provides key habitat for many fish species, as well as performing a vital ecological role cleaning water, stabilising mud and sequestering carbon.

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Marine ecologists from the Cawthron Institute have just completed the first summer of a three-year research project to develop new ways of restoring seagrass meadows - using seeds.

Until recently, it was thought that seagrass in New Zealand, which belongs to the species Zostera muelleri, only rarely flowered and set seed. But the marine restoration team at the Cawthron Institute have discovered there are actually plenty of flowers, although team leader Dr Dana Clark admits the greenish flowers are cryptic and hard to find.

The Haven is one of three study sites near Nelson, along with Waimea and Delaware / Wakapuaka estuaries, for the project Restoring Aotearoa New Zealand's Seagrass Meadows. Over the past summer, the seagrass team has been surveying its field sites and monitoring flowering. The researchers have discovered that flowering begins in October and ends in February, with peak flowering in December.

Dana says the team collected about 3000 seagrass flowers, which were taken back to the lab. Here they were kept in two tanks of bubbling water which marine ecologist Dr Anna Berthelsen describes as a 'seagrass spa.' The bubbles keep the seagrass well oxygenated as they mature, allowing them to develop naturally and shed pollen into the water which fertilises female flowers that go on to develop seeds.

Dana says they were thrilled to collect nearly 600 seeds, which are being stored ready for germination trials. Armed with this summer's findings, she hopes the project will produce even more seeds next summer. …

Go to this episode on rnz.co.nz for more details