Underwater Gardens Seagrasses of the Great Barrier Reef

Seagrasses form meadows in the sea, and are an essential part of the Great Barrier Reef

Although they look like grass or seaweed, seagrasses are neither. They are flowering plants, which have left life on land to live under the sea. Like land plants, they have roots, stems and leaves, and also produce flowers and seeds.

Seagrasses at your service

Supporting marine life

Seagrass communities are vital in supporting our fisheries. The food, oxygen and shelter provided by seagrass supports vast numbers of marine life, including crabs, prawns, nearly 100 fish species, endangered marine turtles and threatened dugong.

Clean, clear water

As they grow, seagrasses form networks of underground stems called rhizomes, which trap and stabilise sediment and absorb nutrients, improving water quality. One hectare of seagrass can absorb 1.2kg of nutrients per year, equal to the treated effluent from 200 people! This helps to improve the health of nearby coral reefs.

Carbon sinks

Seagrasses trap carbon as they grow, and can store it for long periods in the sediment, possibly thousands of years. One hectare of seagrass can store the same amount of carbon dioxide per year as is emitted from a car travelling 3350km. One square metre of seagrass can also produce up to 10 litres of oxygen per day.


The Great Barrier Reef has one of the largest seagrass populations on the planet with 15 out of the approximately 70 species that exist in the world. Seagrass in the Great Barrier Reef World Heritage Area covers 12% – more than coral, which covers 7%.

Seagrass species in our area

Threats to seagrass

How you can help

Water quality issues begin at home and work! Remember that the chemicals you use (for example dishwashing liquid) will eventually end up in the sea. Use environmentally friendly products and avoid artificial herbicides and pesticides if you can.

Take care when boating in seagrass habitats. Lift your outboard motor in shallow water to avoid digging up seagrass with your propeller. When anchoring, avoid dragging, which can damage the seagrass.

When walking at low tide at the beach, avoid unnecessary disturbance and trampling on seagrass meadows.

Get involved!

The health of the seagrass at five sites throughout the region is monitored twice per year by community seagrass volunteers. Supported by Reef Catchments Mackay Whitsunday Isaac and Seagrass-Watch, volunteers collect valuable data on the species and health of the seagrass over time, helping managers to protect this valuable resource for everybody.

You can find out dates and information on how to volunteer by registering for the Coastcare eNewsletter, which advertises all Reef Catchments Coastcare volunteer opportunities, or join the volunteer groups on Facebook for Mackay or Whitsunday.

Looking for more ways to get involved? Visit Seagrass Watch at www.seagrasswatch.org

This project is supported by Reef Catchments, through funding from the Australian Government’s National Landcare Program.