Mangrove Flats at Lamb island


When the tide is low, the rocky shore of Lamb Island with ancient mangroves twisted in beautiful shapes, gleam in the sunshine and glow in the evening light.

Queensland mangroves have always been affected by adverse natural climatic conditions that are manifest seasonally and annually in the first instance, and episodically with severe events. Various natural factors pose significant threats. Changing rainfall conditions result in expansion or contraction of mangrove areas depending on fluctuations in rainfall. Physical damage to foliage and stems is caused by severe wind and hail storms. Sea level rise results in zonal shift that replaces upland vegetation. Other influencing factors include: increased sea surface temperatures and decreased coastal frosts; insect infestations like caterpillar plagues result in significant defoliation inhibiting mangrove growth and survival; storm-wash wrack smothers breathing roots and trees die; and, erosion destabilizing trees and redeposition of fine sediments buries breathing roots to suffocate trees

Mangroves begin as a seed, called a propagule, which germinates while still attached to the tree. The seed has a long cigar-like shape that falls off of the parent tree and either sticks in the mud growing next to the parent tree, or floats off into the ocean. These seeds have a strong, protective covering that allows them to float and survive for long distances and periods of time. When the seedling finally reaches its point of destination, the roots will bury into the ground sending the seedling up into the air forming a new mangrove tree. There are many types of plants located on the earth and, “Approximately 80 species of plant are recognized as being mangroves” (Bellamy & Dugan, 1993).

Mangroves play a role both on land and in the water. In one way in which this plant species is a terrestrial tool is by stabilizing shorelines. The mangrove “wall” between the land and the sea protects the shoreline from erosion and minimizes destruction from powerful waves. Due to mangroves being a naturally flexible plant, they are able to withstand severe damage of winds, waves, and changing tides for thousands of years. Mangroves minimize the loss of property and human lives throughout the globe. Mangroves are such an abundant species that in some areas they form their own islands called mangles. A mangle is, “a term for an assemblage of mangroves interlocked to form patches, which can further extend seaward as a fringe around the shoreline or as a distinct island” (Kraynak & Tetrault, 2003). Mangroves live in shallow water areas and gather sediments that support the root structures. “Mangrove forests help to build up soil along tropical coastlines, buffer from storms, and at the same time provide a habitat for many popular marine organisms such as crabs, shrimps, and oysters”(Prance, 1998).

Mangroves provide a home for many organisms, not only aquatic. All of the different organisms that are found in the mangrove areas are all labeled as being euryhaline-able to withstand wide variations of salinity. Oysters are abundant in these areas. They attach themselves to the roots of the mangroves by hook-like projections from their shells. The raccoons of the Florida Everglades and the crown conch shell eat these oysters. Fiddler crabs run around the mangrove areas during low tide eating plant debris. When the tide returns, they run back to their burrows that they make in the mud. The males have a large claw that they use for communication and defense. The opposite partner has a relatively small claw.

The strangest creature living in the swamps are little fish called mudskippers. During low tide, these fish walk around the mud looking for prey. “Some species have suckers on their undersides that help them to climb rocks and mangrove trees”(Laurie, 1972). Their prey consists of small crabs, mollusks, worms, and insects. The mangrove swamps are also nurseries for many coral fish. The swamps provide a protective area for the coral fish to develop to the point where they can travel further out into the ocean to the coral reefs.

There are many species of birds that live in the mangrove areas. This is an ideal area for these birds to live in due to the easy access to both food and resting area. Many birds have developed special characteristics to their beaks and feet to help them adapt to this environment living off of certain prey. Pelicans and other seabirds live in the canopies of the mangrove swamps. During the breeding season, they form large nesting assemblages of adult birds and their offspring called large rookeries. “Other animals that find shelter in the branches and are adapted to mangroves include bats, Proboscis Monkeys, snakes, otters, the Fishing Cat. As many as 200,000 fruit bats may roost in a mangrove. Some small fruit bats roost in mangroves on offshore islands where it’s safe from predators and commute daily to the mainland to feed. The bats also contribute to the mangrove: Short-nosed Fruit Bat (Cynopterus sphinx) is believed to be the only pollinator of key mangrove trees (Sonneratia)”(Singapore Zoological Gardens Docents, 2000).