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Wyville Thomson Ridge Survey WTR0924S (Blog #4): The survey concludes

By Offshore survey team

Wyville Thomas RidgeOffshore Survey

Our latest blog post is the final update from our offshore survey team on their recent survey to Wyville Thomson Ridge (WTR) Marine Protected Area (MPA) (Survey 0924S).

JNCC and the Marine Directorate of the Scottish Government had a stimulating time sampling in the Wyville Thomson Ridge Marine Protected Area (MPA) and have collected vital information about the site. Thanks to the hard work of everyone on board the MRV Scotia. Though our luck with the weather did not hold throughout the survey, we were able to adapt our survey objectives to make sure we still filled our most important data gaps.

In total, we collected 80 drop frame camera monitoring stations, with the main priority being the stations at the 450m and 800m depth contours, (see Image 1). We also completed a total of 27 CTD stations over three CTD lines across the width of WTR, both inside and outside of the site, (see Image 2).

Image 1. Summary map showing drop-camera stations successfully attempted, and stations not attempted due to change in survey objectives at WTR MPA.

 

We collected environmental data in cross sections through the site and multibeam, full coverage of areas shallower than 450 m. Image 2 shows the multibeam areas. These were split into boxes.

Image 2. Map showing CTD and MBES area where data was collected.

 

With the location of WTR at the southern end of the Faroe-Shetland Channel and the northern end of the Rockall Trough, the different water masses in this area influence the prevailing environmental conditions on either side of the ridge. On the southwest side of WTR, warm North Atlantic surface waters are carried over the ridge by the Gulf Stream, whereas on the northeast side of WTR the Faroe-Shetland Channel directs cold, arctic bottom water southwards.

During our environmental data collection from the CTDs (measuring conductivity (salt concentration of the water), temperature and depth) we could see the dramatic effects of these different water bodies colliding. In the figure below you can see the changes in temperature, the red line of the top plot. The noticeable change happens at a depth of 500 meters, where the temperature drops from + 12.5ºC to -0.5ºC. These CTD plots were taken across the second CTD line, the middle of Wyville Thomson’s Ridge.


Image 3. Top is a CTD profile from the northern side of WTR showing a sharp change in water temperature (red) and salinity (blue) at ~500 m. Bottom is a CTD profile from the southern side of WTR showing a relatively gradual change in water temperature and salinity when compared with the above. This is preliminary data that has not been fully quality checked.

 

The data will provide valuable information to help us learn about the condition of the animals within the MPA, and the habitats that support them.

It is with many thanks to the captain and crew of the MRV Scotia and our Marine Directorate of Scotland colleagues for all their efforts on this survey that we say farewell for now.

You can catch up on how the survey to Wyville Thomson Ridge MPA went from our earlier blog posts:

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