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Existing multibeam bathymetry data were used to assist in the interpretation of seabed habitats. The inshore 1 km zone bathymetry and backscatter data were collected in 2008 through the Southwest Regional Coastal Monitoring Programme. Further offshore, acoustic data collected in 2008 as part of the Maritime and Coastguard AgencyÔÇÖs (MCA) UK Civil Hydrography Programme (CHP) were available (CHP, 2008). The bathymetric data were collected and processed in accordance with the International Hydrographic Organisation (IHO) Standards for Hydrographic Surveys - Order 1 (Special Publication 44, Edition 4) (IHO, 2008). The bathymetry data are archived by the United Kingdom Hydrographic Office (UKHO) and provided as fully processed and cleaned data; the inshore dataset gridded at
1 m resolution, and the offshore data gridded at 10 m resolution. Both datasets were available in Ordnance Datum. A fully compensated and corrected backscatter mosaic, exported as Floating Point Geotiff format, was also available for further analysis (see Appendix 2 for images derived from acoustic data). No further bathymetric surveys have been conducted specifically to provide coverage of the central section of the rMCZ through the MPA Evidence Gathering programme.
Sediment samples were collected in March 2014 by the EA MMS, aboard the Severn Guardian (CruiseID: 2FGL50314; Godsell, 2014), from 16 stations which were positioned within the sedimentary habitats using a triangular lattice grid overlaid on the SAD habitat map. Benthic grabs were used at all stations to collect sediments and infauna. In March 2012 an underwater camera system was deployed at 45 stations by the EA, aboard the Water Guardian (CruiseID: wgdn0112; Godsell, 2014) to collect video and still images of the seabed. (Figure 2; Appendix 1). Video samples were successfully collected at 41 of those sites and stills successfully collected at 44 sites.
Sampling equipment comprised a 0.1 m2 mini-Hamon grab deployed from the stern gantry of the Severn Guardian to collect sediment from the seabed, as described by Ware and Kenny (2011). Sampling positions were recorded (fixed) using Hydropro data acquisition software when the gear made contact with the seabed, with the midpoint of the vesselÔÇÖs stern gantry being used as the default offset for position fixing. Once recovered, the sample was emptied into a suitable container, photographed, and the sample volume measured. A sub-sample (approx. 500 ml) of sediment was removed for particle size analysis (PSA). The remaining sample was washed over a 1 mm mesh sieve to retain the faunal fraction, photographed and preserved in buffered 8% formaldehyde solution for transfer ashore for analysis. A drop-down video camera system was used to acquire video and photographic stills of the seabed, in March 2012 from the Water Guardian survey vessel, following the MESH ÔÇÿRecommended Operating Guidelines (ROG) for underwater video and photographic imaging techniquesÔÇÖ (Coggan et al., 2007). The camera was secured in a drop-down frame along with two high intensity LED strip lights and deployed LandÔÇÖs End (Runnels Stone) MCZ Post-survey Site Report 7over the stern of the Water Guardian. Sampling positions were recorded (fixed) using Hydropro data acquisition software when the gear made contact with the seabed. The mid-point of the vesselÔÇÖs stern gantry was used as the default offset for position fixing. Video footage was recorded on a Sony GV-HD700 in DV tape format and a secondary backup media device. Images of the seabed were captured every 10-15 m, or more frequently in heterogeneous areas of BSH and if particular habitat/species FOCI were observed.
Video and still images were analysed following an established protocol developed and used by Cefas (Coggan and Howell, 2005; JNCC, in prep.; see Annex 5). For further detail on ground truth sample collection see the ÔÇÿLandÔÇÖs End rMCZ Survey ReportÔÇÖ (Godsell et al., 2013) and the ÔÇÿLandÔÇÖs End rMCZ 2014 Survey ReportÔÇÖ (Godsell, 2014). |
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