Seagrass mapping

Seagrass beds are an important habitat as they can serve as nursery areas for a variety of species, and are also known to have a role as carbon, nutrient and chemical sinks and also in stabilising coastal sediments (Orth et al, 2003). They have actually been categorised as the 3rd most valuable ecosystem globally (on a per hectare basis), only preceded by estuaries and wetlands (Costanza et al, 1997). They are a UKBAP Priority Habitat, on the OSPAR List of Threatened and/or Declining Species and Habitats and also are an important feature of estuarine Sites of Special Scientific Interest (SSSI) under the UK Wildlife and Countryside Act 1981. Further the Water Framework Directive (2000/60/EC) requires that the assessment of seagrass quality which considers taxonomic composition, abundance and disturbance sensitive taxa. As such, any development that may have an impact upon a seagrass bed will need to map the seagrass in order to determine the potential impact magnitude in order to both gain consents and determine mitigation measures. The use of acoustics for this purpose is likely to be the most cost efficient method of achieving this.

The image above shows the  processing of acoustic data on seagrass in SONAR 5 Pro. The thick red line is the seabed. Where the line becomes thicker (toward the right of the image) this is the acoustic response of seagrass, giving a more diffuse acoustic return than a hard seabed. The data (Including seagrass height of each ping, volume of seagrass per section and percentage of area inhabited by each section) can then be exported and plotted in GIS.