Today I’m letting out my inner environmental science geek and taking you with me on a walk along the Wynnum Mangrove Boardwalk which is on Moreton Bay and is part of the Moreton Bay Marine Park. I won’t rattle on too much, we’ll mostly just walk and enjoy the sights, but there are a few basic things you need to know about Mangroves before we set off in order to truly appreciate them and their purpose.
This boardwalk takes you into the heart of a grey mangrove Avicennia marine forest. Rich river silts fed from the Brisbane River provide ideal growing conditions for both the grey mangrove and a small number of red mangroves Rhizophora styloza.
The Rhizophoraceae family (Rhizophora, Bruguiera and Ceriops species) successfully reproduce themselves viviparously. Fertilised seeds do not drop from the plants but begin to germinate, growing out from the base of the fruits to form long, spear-shaped stems and roots (propagules). They can grow in place, attached to the parent tree, for one to three years, reaching lengths of up to 1 m, before breaking off from the parent and falling into the water.
Avicennia, Aegialitis and Aegiceras species also produce live seedlings but these are still contained within the seed coat when they drop from the plant. The seed of Avicennia floats until this coat drops away. The speed with which this happens depends on the temperature and salinity of the water. In water of high or low salinity the seed coat is slow to drop off, but in brackish water it is shed quickly allowing the seedling to lodge in the favoured habitat of this species. Higher temperatures also favour faster action. Avicennia seeds can stay alive in the water for only three to four days.
Mangroves are plants that live between the sea and the land, where they are flooded by tides. This is called the ‘intertidal zone’. The word ‘mangrove’ is given to either an individual species (kind) of plant or to a group of unrelated plants, living in areas that are flooded by tides.
So a mangrove may be a tree, shrub, palm, fern, climber or grass – all of them able to live in salt water.
Lets go! The picture below is the beginning of the boardwalk. You can see through the mangroves to the sea.
Note: If you would like a closer look at any of the photos, just click on them and you will see the larger image.
Mangroves are an important part of the food chain for a number of animal species. Mangrove plants produce a large amount of litter such as leaves, twigs. bark, fruit and flowers. Some of this immediately becomes food for creatures such as crabs, but most breaks down before being consumed by other creatures. Bacteria and fungi break down the litter, increasing its protein, making it into food for fish and prawns. They in turn produce waste which, along with the even smaller mangrove litter, is eaten by molluscs and small crustaceans. Even dissolved substances are consumed by plankton or, if they land on the mud surface, by animals such as crabs and mud whelks. Every time the tide goes out, it takes with it carries a great deal of food out to sea, as much as 12,500 tonnes each year. This is dropped over a huge area of the seabed, and feed bottom dwellers, prawns and fish.
Mangroves are recognised by their pencil-like breathing roots that arise from the tree’s radially spreading roots. You can see some in the picture below. This is how the mangrove plants survive in this thick muddy, salty environment that floods twice a day. They send up these finger like extensions to use as snorkels to breathe (taking in extra oxygen at low tide) and stabilise (trees and mud).
The boardwalk goes for approximately 530m.
There is a seat for those who would like to sit and take in the surrounding sights, sounds and smells.
Did you know that mangroves have ‘moods’!
Let’s just take in some of the sights now.
Spot the love heart in the photo below!
The boardwalk takes you right through the mangroves out to the very edge of Moreton Bay.
The bird you see in the photo below is an Ibis.
All on the doorstep of a capital city!
How many Ibis can you see in the photo below?
Look carefully and you can see new life sprouting all over the place. Amazing in an environment so exposed to the elements.
The boardwalk was built in harmony with the mangrove environment. The photo below shows how the boardwalk catered to an existing mangrove tree.
Notice how the mangrove trees lean away from the ocean
We’re nearly at the end!
As we leave the boardwalk, about to walk up the pathway back to our car, we see a rock with a plaque in recognition of the Honourable Tom Burns, former Deputy Premier of Queensland and Member for Lytton 1972 – 1996. Tom lived locally at Wynnum North and as the plaque says “his dedication and commitment to Moreton Bay and its marine life are second to none.”
I hope you enjoyed your walk along the Wynnum Mangrove Boardwalk with me! I didn’t rattle on too much did I? There is so much more to know about mangroves, but I hope that the basic information within this post has given you a better understanding and appreciation for them.
Categories: Wynnum Manly District