Wednesday, 20 November 2013

Signs in the Sand

Hello again from North Norfolk Sandbanks and Saturn Reef Site of Community Importance (SCI), where our survey efforts are continuing.

As Beccy mentioned in Monday's blog, the day shift have been spending most of their time collecting grab samples and video tows, while night shift duties have tended to focus predominantly on acquiring sidescan and multibeam sonar data. My night shift colleagues and I have been assured that this is a result of the survey design and the influence of changing weather patterns (both of which affect which survey methods we employ at any given time), and that we would be foolish to consider it a conspiracy... What we can say with certainty is that this has meant that while the day shift have been carrying out the more "hands on" bits of work, we've been based in the Plotting Room, where we've been collecting acoustic data to help inform groundtruthing.

Cefas scientists Chris Jenkins and Paul Whomersley  interpreting acoustic data in the Plotting Room (Joey O'Connor, 2013) 

The idea behind using acoustic data to inform our groundtruthing efforts is based on the theory that Sabellaria spinulosa reef can be detected from sidescan sonar. A recent paper discussing this can be found by following the link. For information on how sidescan sonar works (and, indeed, what it is) please refer to this document, produced by the Mapping European Seabed Habitats (MESH) project.

As different substrates reflect sonar waves differently (much like a ball dropped on concrete will return further than a ball bounced off mud or sand, all other things being equal), we are hoping to identify the unique acoustic "signature" that reef formed by Sabellaria spinulosa has. Therefore, as we collect the data we check them for possible Sabellaria reef signatures. We then take note of locations where we've seen a potential reef signature. These locations are visited, and we carry out camera tows and grabs to see what is actually on the seabed.

Gas platform (Joey O'Connor, 2013)
In other news, it has been a quite surreal survey working amongst the myriad oil and gas platforms in this part of the world. Attached above is an example of one we passed yesterday. Further images and information on these installations can be found in a recent blog written by our Scientist-in-Charge for this survey, Cefas stalwart Paul Whomersly, who has also been blogging throughout the survey.