No.10 - JNCC/Cefas Partnership Report Series CEND23/15 Cruise Report Monitoring Survey of Croker Carbonate Slabs cSAC/SCI
(010 - 2016)
Wood, D., Jenkins, C., Eggett, A., Judd, A. & Golding, N.
This report is of the CEND 23/15 survey which was undertaken to contribute to the development of a monitoring time-series for Croker Carbonate Slabs cSAC/SCI.

Abstract

The monitoring survey of the Croker Carbonate Slabs candidate Special Area of Conservation (cSAC) and Site of Community Importance (SCI) was carried out from 24 October – 06 November 2015.
There were four key aims of the survey:
 
1. Revisit sample stations where MDAC has been previously subject to δ13C isotope analysis or stations where its presence was suggested from seabed imagery (potential MDAC) within the site boundary.
2. Improve our knowledge of the distribution and spatial extent of MDAC within the site.
3. Improve our knowledge of areas adjacent to site; confirm the presence of MDAC, map the finer spatial extent and gather more detailed information on biological communities.
4. Characterise the wider sediment areas found within the site.
 
A variety of data types were collected during the two-week survey including multibeam echosounder bathymetry and backscatter, sidescan sonar, EK60 echosounder, deep-tow boomer, high resolution video and stills, benthic samples and water samples. In addition, a pumped METS methane sensor was fitted to the camera drop-frame.
 
Weather conditions were predominantly good throughout the survey period, though some operations were affected by strong winds combined with extremely strong tides. While no major changes were made to the survey plan, minor modifications such as reorientation of survey lines (to maximise time efficiencies while working with the prevailing conditions) were made. Work in some areas was also limited by the presence of static fishing gear. Due to the good weather, the vessel was able to remain on site and work continuously, with no need to make use of the weather contingency sites. That being the case, the majority of the survey objectives were completed, with only a small amount of sidescan sonar and groundtruthing outstanding.
 
Indicators of the presence of methane, including active gas seabed seepage, and extensive formations with the appearance of MDAC were identified. Samples of this potential MDAC were collected using a mini-Hamon grab from a number of stations across the site, and will be subject to further detailed analysis in the near future.
 
 
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Available free from JNCC
A4, 118pp
ISSN 2051-6711
 
Please cite as: Wood, D., Jenkins, C., Eggett, A., Judd, A. & Golding, N., (010 - 2016), No.10 - JNCC/Cefas Partnership Report Series CEND23/15 Cruise Report Monitoring Survey of Croker Carbonate Slabs cSAC/SCI, A4, 118pp, ISSN 2051-6711