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After 20 years of diving in various places around the world I finally had an opportunity to visit Scapa Flow to work with some researchers from Heriot Watt University. Scape Flow is considered, by many to have some of best wreck diving in the world, although if I’m honest I’m not that interested in wreck diving, or rather I should say I’m not really interested in the wrecks themselves. I am interested in the marine life they attract however, and those in Scapa Flow have been there for long enough to attract a fair amount, but it was really the natural marine habitats found away from the wrecks that were of most interest on this trip.

The main purpose of the survey was to determine the extent and quality of the North Cava horse mussel bed but also focused on two Heriot Watt University PhD projects on the restoration of biogenic reefs, specifically Modiolus modiolus (Horse mussels) and their ability to act as nursery grounds for commercially important fish and shellfish species. Modiolus reefs support high levels of species biodiversity providing valuable ecosystem services but are particularly sensitive to certain types of fishing, especially trawling or dredging. As a result they are currently listed as a threatened habitat throughout the Northeast Atlantic and thus are highlighted as a conservation priority.


In addition some of the researchers were also looking at the horse mussel bed’s relationship with the protected archaeological wreck site of the SMS Karlsruhe. Particular emphasis was put on public engagement with some of the research being filmed by the BBC for The One Show.

Diving on the SMS Karlsruhe
Dr Bill Sanderson interviewed for the BBC One Show

We spent a week diving in and around Scapa Flow aboard the M/V Halton skippered by Bob Anderson documenting the work of the researchers as they monitored their survey sites and collected samples. The majority of the diving was done away from the wrecks on Modiolus beds many of which were covered in dense carpets of brittlestars.

Modules filled with substrate to assess variations in larval settlement

One of the projects was investigating techniques for promoting recovery rates through direct intervention. By deploying in-situ modules filled with different substrates the project aims to assess larval settlement, post-settlement survival and environmental conditions conducive to reef development by monitoring larval recruitment and reef development on these different substrates. The key output of the project will be a ‘toolkit’ of techniques used for promoting reef restoration in degraded areas.

Awaiting the Halton