Habitats Of The Reef

Linking the Habitats of the Great Barrier Reef

When we think about the Great Barrier Reef, we typically visualise diverse corals, a magnitude of fish species and marine life. Very few of us consider the neighbouring habitats that connect to the Great Barrier Reef, like the tropical rainforests, coastal estuaries and fringing reefs. 

These habitats are vital to the reef, as they create nursery grounds, feeding areas and provide nutrients and energy to our coral reefs. Primarily, these systems are connected by the movement of water, let’s look at the different ecosystems that collectively create “The World Heritage Great Barrier Reef”. 

Tropical Rainforests

The North-Queensland tropical rainforest is the oldest rainforest in the world, and home to unique plant and animal species found nowhere else in the world. This ancient rainforest has World Heritage Status, making Far North Queensland the only place in the world where two world heritage sites meet. Fresh water collected in the rainforest mountains makes its way to the reef and connects the land to the numerous coral reefs of the Great Barrier Reef.

During the wet season, high rainfall causes flooding of the forest floor, which washes nutrients through our waterways, coastal habitats and out to the reef. Nutrients are a vital source of energy and provide fuel to our phytoplankton. These photosynthetic planktonic organisms in turn form the base of all marine food chains.

Mangroves

The coastal creeks lead to the rivers that flow through our mangrove line estuaries. Nearly 50% of the world’s mangrove species occur in North Queensland waterways and mangroves absorb up to five times more carbon from the atmosphere than other trees.  Mangroves play a vital role in protecting coastlines, filtering nutrients and trapping phytoplankton. They supply food, provide shelter and act as nurseries and breeding grounds for many fish and crustacean species. For example, baby snapper like the Mangrove Jack grow up in the tropical rivers and mangrove estuaries and then migrate 10’s of kilometres offshore to the coral reefs to spend their adult years.

Coastal Estuaries

The coastal estuaries are flanked by shallow water seagrass habitats. Seagrasses are underwater flowering plants, and similarly to mangroves, they stabilise the seafloor preventing erosion. Seagrasses are also great sequesters of carbon. Seagrass beds are nursery grounds for juvenile fish and prawns, some of which play a vital role in our commercial fishing industries. 

Highly productive seagrass beds provide food for several large marine species. For example, the Green Sea Turtle gains 97% of its food from foraging on lush seagrass and using this energy to migrate to many coral reef cays to breed and nest. The diverse habitats of the Great Barrier Reef provide important feeding and breeding grounds for vulnerable species.

Coral Reefs

Coral Reefs only represent 6% of the Great Barrier Reef Marine Park, but are some of the most diverse habitats on the planet. This high diversity is strengthened and supported from linkages to surrounding ecosystems. Fringing Reefs are the first reefs that you will reach, once you leave the coast behind. Most continental islands in the Great Barrier Reef are surrounded by coral.  As we travel further from the coast you will discover patch reefs and ribbon reefs. Species composition varies across the continental shelf.

At the continental edge or where the furthest reefs from the coast are, the Great Barrier Reef meets the open ocean. At this interface, complex oceanographic processes occur, which push deep cold nutrient rich water up onto the continental shelf. These extra nutrients regularly fuel plankton communities that surround coral reefs and provide additional energy to individual coral reefs. This is also the areas where ocean giants like whale sharks and giant black marlin can be found. Giant Black Marlin aggregate off the reefs of Cairns every Spring to Spawn. 

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