Estuaries: mixing places

Did you know that Sydney Harbour is an Estuary? Like all Estuaries, the Harbour is a mixing place of saltwater from the ocean and freshwater from the rivers.

Imagine that you are holding an invisible basketball – this ball will be your Estuary. Your body, arms, and hands represent the land. The space between your two wrists is the freshwater flowing down through the river currents into the Estuary space between your hands.

Outside your hands is the ocean. The waves crash against your fingers, but can’t get into your Estuary except through the small entrance between your fingertips. The ocean tides move slowly through this entrance, mixing with the freshwater in your Estuary.

This makes Estuaries a great mixing place for animals too. Many fish, crabs, prawns, snails and other creatures use Estuaries as a nursery where their children can grow big and strong before going out into the open ocean.

First Nations people also recognise and use Estuaries as mixing places. With abundant foods and resources for making tools, Estuaries are places that can be relied on throughout the year and continue to be important gathering places. Many First Nations foods can be found in Estuaries – everything from fish, crabs, eels, and oysters to the salty leaves of mangrove trees used to flavour cooking.

Our Estuaries are precious places. Along with providing food, materials, and animal homes they give us the lakes, bays, lagoons, harbours, and inlets where many people live and go for fun. This also puts them at risk of being damaged and polluted, so it is important that we all work together to protect our estuaries and keep them healthy.

Here are some things you can do to help:

• If you’re out on a boat or other motorised watercraft, check for oil leaks regularly and avoid sensitive areas like seagrass beds.
• Trash belongs in the bin, not on the ground or in the water! Even rubbish far from the coast eventually finds its way into the waterways.
• Avoid using fertilisers and pesticides on your garden and put grass clippings in the bin – these wash off your plants and into the waterways when it rains.
• Volunteer with a community group to help plant native Estuary vegetation, remove weeds, and clean up rubbish.

Editorial note: Some ecosystem names have been capitalised to give agency to Country by First Nations writers. Find out more about why we capitalise English language in reading Who is Country.

Sara Kianga Judge is a neurodiverse Walbunja-Yuin woman who grew up on Burramattagal Country. She is an environmental scientist, geographer and artist passionate about accessible science communication and helping people to grow meaningful relationships with Country.