Frankland Islands Eco Walk
Frankland Island Marine Biology Walk Information
Normanby Island which is part of the Frankland Islands group is very unique, comprising a continental island and a coral cay. The continental island was formed when the Great Dividing Range was formed and since the sea level has risen, it has remained exposed. Over time corals have settled around the island and due to the natural process of wave action, sediments have started to accumulate. It is the continual build up of these sediments that have formed a coral cay.
Vegetation – Succession
Many of the species of plants what are growing on the littoral fringe of the island originated from other islands or the mainland. Their seeds are buoyant and would drift up with the high tide, and grow from there. The plants situated in the middle of the island originated in two ways. Firstly, the occurrence fruit bats and birdlife nesting on the island which have eaten fruit from other islands or the mainland. They would fly here and do their droppings, their guano would fertilize the seeds in the fruit and the plant would grow from there. Secondly, as the soil quality improved and the shade created from other plants reduced the temperatures in the middle of the island, vegetation from the continental part of the island was able to grow in these more habitable conditions. This helped to stabilize the sediments on the island and enabled more sediment to accumulate making the coral cay larger. This process is known as succession. The forming of an ecosystem which previously did not occur.
| Tour Type | Pricing | Point of Difference | Photo Gallery | |
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| Frankland Island Snorkelling | $139 AUD | All of their tours include: Fresh Tropical lunch with seafood Glass bottom boat or semi-submersible coral viewing tours Guided Island Walk Reef Ecology Presentation Maximum 100 People All day snorkelling plus equipment Morning and Afternoon Tea |
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Mangroves
Mangroves are a group of plants that have adapted to be able to live in very salty, unstable, low oxygen conditions. This particular mangrove is also known as a pioneering mangrove which means it often grows on the fringe of river mouths or edges of islands, like it is here. It has many special adaptations including those little peg roots you can see under the water (pneumataphores). This extensive root structure helps to stabilize the plant, it acts as a little snorkel helping the plant to breathe, and also is an ultra-filtration mechanism reducing the amount of salt that enters the plant. Any salt that does enter the plant and is not required by the plant is stored in old leaves. Once the leaf becomes too toxic with salt, the plant simply discards the leaf, removing the salt from the system.
Coral Rubble
What you may be standing on may look quite destructive but it is a natural process carried out by wave action. In this case most of this coral rubble was deposited here by a couple of cyclones (Joy and Winefred) in the early 1990's. And as you will see most of the rubble is staghorn coral (Acroppora spp.), which is a fast growing species – about 15cm a year. It is very susceptible to wave action but it is similar to a bush fire on the mainland. It wipes out large sections of reef and allows different species to settle and grow. This pile of coral rubble also helps to buffer the island behind it from wave action.
Beach Rock
This structure that you will be standing on is what is known as beach rock. It is formed from the skeletons of coral you will see around the island. Coral skeletons are made from Calcium Carbonate which is also known as limestone – a key ingredient in cement. With all the coral piled up, the weathering process of rain and high tides dissolves some of the limestone and puts back into solution. Over a period of time this hard porous structure is formed. It is actually the fastest forming sedimentary rock.
Rock Pools
Intertidal rock pools are home to many free living and sessile marine organisms. The rock pool itself is a very hostile ecosystem. Their can be multiple plants and animals sharing a very limited supply of resources. As the tide goes out and the rock pool has separated from the ocean there is a large reduction in mixing of the water column. This, along with the organism's respiratory processes, uses up the dissolved oxygen in the water which can cause 'drowning' of certain animals. Additionally, evaporation of the rock pool increases the salinity of the water, often having a toxic effect for certain organisms.
Frankland Islands is one of Cairns most natural and most beautiful uninhabited Islands you can visit from Cairns on a day trip. We highly recommend it.