Background: When conducting biological surveys scientists use long lines called transects that cross through a community and provide a reference point along which observations can be recorded.

In underwater surveys in water divers use transect lines to find out about marine habitats. Where water is too deep or difficult for divers to visit, video cameras are towed behind a boat and the data collected is later analysed to work out what is found in an area. Scientists are interested to know what material is found on the sea floor and what changes in the type of habitats are found in different areas.

Information collected using video tows can be matched with the information obtained from the multibeam sonar images to accurately predict what the different textures on the multibeam images represent in terms of the type of materials on the sea floor and the various living communities. This information is then used to create habitat maps.

Method:

• Watch the video clip several times to get a sense of the changes that occur in this section of the Marine National Park
• Using the distance information provided with the video clip use the table to record any changes that are observed in the type of materials that occur on the sea floor. Record these as sand or rock on the table.
  
• Repeat the clip and this time observe where kelp (brown seaweeds) occur and record this on the table.
  
• Repeat the clip again and this time make note of any sponge habitats that found along the bottom.
  
• Finally record the presence of large groups of fish or other animals.
• Using different symbols to represent the differences you have noticed construct a linear picture of the different communities as they are found along the transect.