Structure and function of mangrove forests and their associated mudflats

Dr Trevor Tolhurst and Professor Gee Chapman


Background
A mangrove forest and associated mudflat

Intertidal sand and mudflats fringe the coastlines of many countries. These areas form low-slope flats and in Australia are often associated with mangrove forests. Extensive mangrove forests exist in Queensland, Northern Territory, northern Western Australia and northern New South Wales. Small patches can be found as far south as Victoria and in South Australia and southern Western Australia. Despite the extreme conditions of low tide and variations in salinity, mangrove forests (and their associated mudflats) are highly productive habitats, with a gross primary productivity equal to that in many terrestrial habitats.

They are important habitats for many marine animals, especially small fish that shelter and feed amongst the mangrove roots. Mangroves are also thought to play a vital role in protecting the coastline against erosion by wave-action and act as a source and sink of sediments and pollutants. Unlike mangroves in northern Australia that are minimally affected by human activity, mangroves in Sydney Harbour have been directly affected by human development and, as a result, have been fragmented into small patches of forest. These fragmented habitats may exhibit different structural and functional characteristics from those in less impacted habitats.

Aims

This project will investigate the structure and function of mangrove habitats, eventually comparing impacted and less-impacted areas to understand the effects of human activity on these important habitats. This knowledge can be used to manage these habitats, prevent further deterioration of them and assist in efforts to restore damaged habitats. It is expected that structure and function will be determined by an interaction of biological and physical processes and properties. Specialised freezing techniques will be used to sample sediments in situ to provide "snap-shots" of the properties and processes occurring.

Contact coring
Results

Initial field measurements have been taken; data indicate the habitats are spatially and temporally variable, exhibiting a complex interaction between physical and biological processes and properties. This presents a challenge in identifying the controlling factors that are most significant.