Offshore Benthic Survey

Offshore activities and development (such as dredging or offshore wind farms) often require surveys of the seabed under the Marine and Coastal Access Act 2009 as well as Conservation of Habitats and Species Regulations 2017 if the activity or development may impact on a protected site.

These surveys are to establish the baseline ecology or monitor the seabed post-construction and investigate potential impacts especially if habitats such as reefs or offshore sandbanks are present which are on Annex 1 of the Habitats Directive.

Surveys can utilise one or more methods:

  1. Grab sampling – this is generally utilised on sediment seabed where the fauna is mainly within the sediment and involved taking up to ten litres of seabed which is then sieved to isolate the fauna for identification. Subsamples are also taken so that the sediment can be accurately characterised.
  2. Drop down camera or ROV – this is a not-destructive method and is generally used on seabed with sensitive habitats (such as reefs) or where bedrock is present. A camera is deployed to the seabed with a live video link to the survey vessel so that a biologist can take video and stills images of the seabed for later analysis of fauna and algae.
  3. Fish survey – this can be done with fishing gear such as trawls or with baited video and is used to provide semi-quantitative data on the community of fish and invertebrates that live on or just above the seabed.

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