Using remote sensing to obtain information about mudflats

Dr Richard Murphy, Dr Trevor Tolhurst, Professor Gee Chapman and Professor Tony Underwood


Background
Camera image before it was analysed by computer

Inter-tidal mudflats are important habitats for a large variety of animal and plant species. They perform many ecological functions by providing spawning grounds for fish, habitats for birds, reptiles and other important fauna as well as protecting the coastal zone from erosion. Mudflats are highly productive environments and as such they can be viewed as the 'pasturelands' of the intertidal zone. At the base of the food chain are microscopic plants called algae which help to stablise the mud surface and prevent it from being eroded by tidal action or heavy rain. Despite the importance of mudflats, there is relatively little information on how they function as an ecosystem. It is therefore necessary to obtain information on the biological and physical processes that occur within them and how these change from area to area and over time.

Traditionally, samples of mud are collected and analysed in the laboratory but this is an expensive, time consuming process and cannot obtain measurements at very fine (millimetre) spatial scales. A method called remote sensing is being used to gather information about mudflats without disturbing them to the same degree as traditional methods of sampling. Remote sensing uses pictures of the surface of the mud and uses computers to analyse them.



Aims

The aims of this project are to:

· Use remote sensing to obtain information about the sediments in mudflats and the concentration of algae on the mud surface and how they change over time and from place to place.

· Determine the best ways to extract information on algae and sediment from remotely-sensed images of the mud surface. This work is currently being done using photographs obtained from the ground. Images will later be taken from aircraft flying over the mudflats and this will enable information to be obtained over large areas.

· Gather information about the stability of mudflats using other instruments such as the Cohesive Sediment Meter and determine how this information compares with measurements made with remote sensing.








Importance
The same image after computer analysis to calculate how much chlorophyll (or algae) is present

This research will provide new approaches to the measurement of micro-algae and sediment size at small spatial scales without disturbing the environment.

In combination with other work in the Centre this ability will help broaden our understanding of the effects of micro-algae on the stability of mudflats. The maps of micro-algae can also be combined with other data about the distribution of animals, sediment and organic matter to determine how different components of the mudflat function in relation to each other.



Results

Images of the surface of the mudflat have been obtained using a special camera. To show how much algae is present, the images have been analysed using a computer. To do this, the computer detects and measures chlorophyll in the algae, rather than measuring the algae themselves. Many of these images are being used to build up information on how algae change over time and at different locations.