The mangrove ecosystem
Mangroves are tree and shrub species that are adapted to grow in the tidally inundated, salty foreshore area of coasts.
Mangroves have several special adaptations for their environment, including special roots, salt excreting glands in their leaves, and special
seeds to colonise mud flats. Their roots have extensions called pneumatophores which grow upwards out of the salty, anaerobic mud to reach
the air the plant requires. The tangle of roots in the mangrove swamp traps decaying plant and animal matter and helps make the waters of the
mangrove forest extremely nutrient rich.
Mangrove forests are important nurseries for many fish that come here to spawn and leave the young to grow in relative safety from predators
and the hazards of the open ocean. The mangroves provide a good nutrient supply from decomposing organic matter as well as shade and
shelter for young animals.
These nurseries are often important for commercially targeted fish and invertebrate species.
Mangrove forests are important for coral reef ecosystems close to land. The mangrove forest provides a buffer zone between the coastal zone
and the open ocean, trapping sediment as it is delivered to the coast in run-off. This is an important aspect for coral reef development as it is
imperative that the waters of the open ocean are clean and free of sediment.
The main habitats in the mangrove forest are the mud, the water, and in or on the trees and shrubs.
Animals that you might find in the mangrove forest might include crabs, molluscs, terrestrial insects and spiders, mudskippers (fish that
walk over the mud on their pectoral fins), shrimps, prawns, jellyfish, and fish. These animals often use the mangrove for only a part of their
life cycle, such as juvenile fish.
Other animals use the mangrove daily, coming in with the tide to feed on the abundant invertebrate life amongst the mangroves and heading
back out to sea at low tide. There is a very strong tidal pattern of behaviour in a mangrove swamp, with animals such as fish, shrimps and
jellyfish active at high tide, and crabs and snails dominating the mudflats at low tide.
Ecosystem 5: The Mangrove Swamp
Mangroves are tree and shrub species that are adapted to grow in the tidally inundated, salty foreshore area of coasts.
Mangroves have several special adaptations for their environment, including special roots, salt excreting glands in their leaves,
and special seeds to colonise mud flats. Their roots have extensions called pneumatophores which grow upwards out of the salty,
anaerobic mud to reach the air the plant requires. The tangle of roots in the mangrove swamp traps decaying plant and animal
matter and helps make the waters of the mangrove forest extremely nutrient rich.
Mangrove forests are important nurseries for many fish that come here to spawn and
leave the young to grow in relative safety from predators and the hazards of the open
ocean. The mangroves provide a good nutrient supply from decomposing organic
matter as well as shade and shelter for young animals. These nurseries are often
important for commercially targeted fish and invertebrate species.
Mangrove forests are important for coral reef ecosystems close to land. The
mangrove forest provides a buffer zone between the coastal zone and the open ocean,
trapping sediment as it is delivered to the coast in run-off. This is an important
aspect for coral reef development as it is imperative that the waters of the open ocean
are clean and free of sediment. The main habitats in the mangrove forest are the
mud, the water, and in or on the trees and shrubs.
Animals that you might find in the mangrove forest might include crabs, molluscs, terrestrial insects and spiders, mudskippers
(fish that walk over the mud on their pectoral fins), shrimps, prawns, jellyfish, and fish. These animals often use the mangrove for
only a part of their life cycle, such as juvenile fish.
Other animals use the mangrove daily, coming in with the tide to feed on the abundant invertebrate life amongst the mangroves and
heading back out to sea at low tide. There is a very strong tidal pattern of behaviour in a mangrove swamp, with animals such as fish,
shrimps and jellyfish active at high tide, and crabs and snails dominating the mudflats at low tide.
Mangroves at North Keppel Island and Zones with in the
mangroves
As a general rule, zones of dominant mangrove species run parallel to the shoreline or to the banks of tidal creek systems. The
seaward side of the community is likely to be dominated by a fringe of grey mangroves (Avicennia marina) as it is best adapted to
early colonisation and a wide range of soil conditions. Avicennia marina is a tough mangrove species; it is Australia’s most common
mangrove species because of its ability to tolerate low temperatures and a variety of other intertidal conditions. A pioneer, it is likely
to be the first species to grow on newly-emerged mud banks, putting up its distinctive peg roots.
The next zone might be inundated only by periodic spring tides at the times of new and full moons. The soil will be firmer, but it
contains more saline due to the evaporation of water leaving behind salt which will not be diluted until the next spring tide. The more
specialised yellow mangrove (Ceriops) species can be found in this zone, although conditions usually make it impossible for
anything other than saltmarshes or saline herblands with succulent plants to thrive here. The resilient grey mangrove can appear
again.
A number of factors may determine what happens to the landward side of this zone. In conditions of high rainfall — as occurs in
north Queensland, particularly in the Daintree — regular flooding may lead to freshwater swamp areas dominated by the less salttolerant littoral margin (shore) species (such as cottonwood Hibiscus tiliaceus). The Milky mangrove is also found along the shore
line at North Keppel Island. Behind this may be a zone of paperbark swamps or wetlands. These trees and zones are all found at
North Keppel Island.
In areas of high seasonal rainfall, such as the Gladstone to Townsville region, the reverse may be the case, with evaporation and little
fresh water input leading to an increase in salinity. This could be a saltmarsh or salt flat zone where only the toughest yellow
mangrove (Ceriops tagal), club mangrove Aegialitis annulata and grey mangrove (Avicennia marina) grow in patches bordering
coastal saline herblands.
The greatest concentration of mangrove species is usually at the mouth of tidal creeks and rivers where salt and fresh water mix in
ideal proportions and floodwaters deposit plenty of material to build up the banks.
Grey Mangrove (note pneumatophores)
Yellow mangrove (note buttress roots)
What is a mangrove?
A mangrove is a woody plant or plant community that lives between the sea and the land in areas inundated by tides. Thus, a mangrove is a
species as well as a community of plants. The species can be a tree, but it can also be a shrub or palm. All share the ability to live in salt water.
Did you know?
North Keppel Island has 3 types of mangroves.
The Yellow, Grey and Milky mangrove. The
native hibiscus may also be considered a mangrove.