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Celebrating Snells Beach's seagrass

By Lyn Hamilton-Hunter

Royal spoonbill (kōtuku ngutupapa) feeding in seagrass meadows at Snells Beach.
Royal spoonbill (kōtuku ngutupapa) feeding in seagrass meadows at Snells Beach.

Snells Beach got off pretty lightly during the Auckland floods and Cyclone Gabrielle, which ravaged many parts of New Zealand in the 2023 summer. There are many contributing factors for the minimal impact on the Snells Beach shoreline but one thing is for certain, we have really benefitted from the seagrass meadows.

There may be complaints about it because some people see seagrass as unattractive and it might detracts from their enjoyment of the beach. However, there is little doubt the seagrass helped save Snells Beach from more storm damage.

Seagrass at Snells Beach absorbs wave action and improves water clarity

The built-up piles of floating seagrass, acted as a wave suppressor during the storm.

Seagrass mounds at Snells Beach absorb wave action.

The seagrass meadows growing on the flat tidal beach give stability to the sand.

You may have noticed Snells Beach does not suffer from rip tides or changing channels. In part, this is because the suppressed wave action does not change the landscape as much as it does at beaches such as Omaha.

It was quite fantastic to see when paddling out over the bay just 36 hours after Cyclone Gabrielle, the water was lovely and clear within the confines of Snells. However, once getting to Brick Bay or the rocks south to Algies Bay, the turbidity increases, the clarity was diminished.

“Dense meadows of seagrass can stabilise the sea bed and reduce erosion. Seagrass leaves trap fine sediments and reduce particle loads in the water by slowing water movement and encouraging particle deposition, which improves the water clarity. Seagrass plants absorb nutrients from the water and seabed." New Zealand seagrass, 2009, Niwa

In addition, seagrass is the reason why Snells Beach supports so much wildlife.

"They also release oxygen from their leaves and roots, which is beneficial for other biota and stimulates nutrient cycling. Decaying seagrass is decomposed by bacteria and fed on by small marine animals (particularly snails but also worms, bivalves, and crabs), both within and adjacent to seagrass meadows, supporting the marine food web." New Zealand seagrass, 2009, Niwa

Seagrass provides feast for Snells Beach wildlife

Bar-tailed godwits, pied stilts, royal spoonbills, oystercatchers, herons, kingfishers, dotterels, marine fish, invertebrates, bivalves all benefit from smorgasbord of rich food created by the stable seagrass environment.

"The small crustaceans and worms that live in seagrass meadows are important sources of food for wading birds (such as the oyster catcher, pied stilt, royal spoonbill, bar-tailed godwit) and fish (such as mullet, stargazers and juvenile flatfish. Snapper and leatherjacket juveniles, mullet, trevally, garfish, parore, spotties, pipefish and triplefins are often abundant in subtidal seagrass meadows in particular, but also reside in intertidal meadows when the tide is in." New Zealand seagrass, 2009, Niwa

“Seagrasses are foundation species that inhabit shallow waters of most of the world's coasts and contribute substantially to ecosystem services. They are a polyphyletic group of monocotyledons, order Alismatales that reinvaded the marine environment around 80 Ma. There are high frequencies of dioecy among species and hydrophilous pollination, uncommon in flowering plants. In addition, they tolerate a saline medium, grow submerged, have an anchoring system to withstand tidal and wave action and can disperse in the marine environment. Seagrasses are under increasing pressure from human activities and globally are declining at a rapid rate” The movement ecology of seagrasses, 2014, The Royal Society

And, don’t forget many of us also benefit from a wonderful mulch for our gardens.

So…. let us celebrate our luck that we have this incredible natural resource on our doorstep.



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