Sea grass

by Nicola Hartfield


Galaxies of life
Co-existing in balance, bountiful splendour
Bees of the sea sow my seed.

Fine fingers of green filter the saline tides
Quietening their urgency as they greet river’s mood.
Invited guests gather to feast
In calm communion.

On the horizon dark shadows loom
The scales of nature are tipping.
A fog of dread descends like ash
Upon our last supper.

I gasp for sun’s sparking rays through muddied waters
Clinging to starved sediment that can no longer hold me.
My existence, now owned by others, lies beyond my reach.

Homesick, I cry for my past
Galaxies of life.


‘Seegrass’

Seagrass – Angiosperm

Estuaries, Whanganui, New Zealand. Writer, Nicola Hartfield. Artist, Roz Paterson.

Thirty-five years ago, I swam in a meadow of seagrass. It was a most surprising and wonderful experience. I came upon it by chance scuba diving in the Pacific Ocean.  I never knew that grass grew in the sea, nor did I know that it grew in estuaries.

Seagrass are flowering plants adapted over millions of years to allow them to live under water and in different conditions. There are around 72 species of seagrass in the world.[1] Seagrass can be eaten so it is a vital part of the food chain.

Unlike land plants that receive oxygen from the soil around their roots, underwater grass exchanges oxygen and carbon dioxide through its thin leaves. Seagrass is the greatest contributor of carbon reduction, able to bury carbon forty times faster than tropical forests can bury carbon in their soil.[2]

For this project, Roz Paterson [3] and myself researched the Whanganui estuary. It is large (353 ha), shallow, and has a tidal influence that extends 12 km inland. [4]

Estuaries are nurseries of the sea providing a feeding and breeding ground for many fish, migratory and wading birds, freshwater and estuarine species of snail, cockles, worms and small crustaceans and crabs. They are a partially enclosed body of water with connection to the open sea, situated at the mouth of rivers and streams. Estuaries are designed to filter out underwater soil (sediment) and pollutants from rivers and streams before they flow into the ocean.

A vital feature of the health of an estuary is its seagrass. Seagrass is sometimes referred to as an ecological engineer due to its ability to use its strong roots and long leaves to calm the water and reduce nutrient levels and sediment particles floating in the water. The still water can absorb the sunshine needed to reach the grass, allowing it to flower. When flowering occurs once a year, the crustaceans (bees of the sea) pollinate it.

Historically the Whanganui estuary has received little attention, but since 2009 the Department of Conservation has provided broad scale habitat mapping to the area, providing information about sediment and eutrophication risk (the build-up of minerals and nutrients), habitat features, monitoring recommendations and priorities to the Regional Council.

Humans pose the greatest danger to estuaries due to overfishing, flood and erosion protection structures, pollution, reclamation of land close to estuary, the introduction of weeds by foot and vehicle, farm and industrial run off.

The Whanganui estuary has very little salt marsh and no sea grass. Its sediment, mainly soft and mud dominated, is rated as poor. There is no trace of excessive organic matter or eutrophication. Although it is species poor with only two varieties of sea snail, there are high volumes of them. The Whanganui estuary will be monitored every five years at two separate sites and with the possibility of a third monitored site created.[5]  


[1] Secret Gardens Under the Sea: What are Seagrass Meadows and why are they important. 2018 Cullen-Unsworth,L., Jones,B., Lilley,R., & Unsworth,R.

[2] Secret Gardens Under the Sea: What are Seagrass Meadows and why are they important. 2018 Cullen-Unsworth,L., Jones,B., Lilley,R., & Unsworth,R.

[3] Roz Paterson. Illustrator.  https://www.rozpaterson.com

[4] SAFE ECOLOGY; Barrie Forrest, Keryn Roberts & Leigh Stevens (29/4/2021) Report commissioned by Horizons Regional Council.

[5] SAFE ECOLOGY; Barrie Forrest, Keryn Roberts & Leigh Stevens (29/4/2021) Report commissioned by Horizons Regional Council.

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