259d15ca422e9a6a6669106a683918e6 English dataset Cornwall Inshore Fisheries and Conservation Authority Data Officer Cornwall IFCA Research Team enquiries@cornwall-ifca.gov.uk pointOfContact 2024-07-23 MEDIN Discovery metadata standard 2.3.8 urn:ogc:def:crs:EPSG::4326 2021 Cornwall Inshore Fisheries and Conservation Authority (IFCA) Cawsand within the Plymouth Sound and Estauries Special Area of Conservation Acoustic Survey of the seagrass bed 2021-10-05 publication 2021_CIFCA_MX_CAW_Seagrass Cornwall Inshore Fisheries and Conservation Authority (Cornwall IFCA) carried out a survey to map the extent of the seagrass at Cawsand, within the Plymouth Sound and Estuaries Special Area of Conservation (SAC). The survey was carried out to provide Cornwall IFCA with an updated extent map of the seagrass. The seagrass at Cawsand is the only bed in the Plymouth Sound and Estuaries SAC which is within the Cornwall IFCA district, the remaining seagrass beds (Drake’s Island, Cellar's Cove, Red Cove North, Red Cove South, Tomb Rock, Jennycliff South, Jennycliff North and Firestone Bay) are within the Devon and Severn IFCA district. The aim of the survey was to map the extent and coverage of the seagrass bed at Cawsand within the Plymouth Sound and Estuaries SAC using a Biosonics MX Scientific Echosounder. In total 64 MX tows were completed of which 62 were included in the analysis. Sea conditions were favourable throughout the survey. Research Team Cornwall IFCA Cornwall Inshore Fisheries and Conservation Authority enquiries@cornwall-ifca.gov.uk originator Research Team Cornwall IFCA Cornwall Inshore Fisheries and Conservation Authority enquiries@cornwall-ifca.gov.uk custodian continual Geographic Information System Marine Environmental Data and Information Network NDGO0005 Habitats and biotopes GEMET - INSPIRE themes, version 1.0 2008-01-06 revision Habitat extent SeaDataNet P021 parameter discovery vocabulary 2009-11-16 revision Data is freely available for research or commercial use providing that the originators are acknowledged in any publications produced and permission must be sought if the data will be reproduced in full or part or if used in any analyses. otherRestrictions No restrictions to public access English biota Charting Progress 2 Sea Areas 2009-06-18 creation Western Channel and Celtic Sea ICES Rectangles 2009-05-01 creation 29E5 SeaDataNet vertical extent keywords 2010-01-01 revision water column -4.2003 -4.1900 50.3255 50.3373 2021-08-23 2021-08-23 Research Team Cornwall IFCA Cornwall Inshore Fisheries and Conservation Authority enquiries@cornwall-ifca.gov.uk distributor dataset MEDIN data guideline for sidescan sonar (SSS) data 2012-04-30 publication See the referenced specification true Historic survey data of seagrass at Cawsand within the Plymouth Sound and Estuaries SAC were downloaded using the latest marine data release provided by Natural England and EMODnet and a 40 m buffer was created around each bed. These positions were uploaded onto HYPACK MAX Version 2019 software. For each polygon, survey lines were created depending on the aspect of each individual bed so that the survey lines ran perpendicular where possible to the coastline following the Environment Agency methodology of subtidal seagrass monitoring for the Water Framework Directive (WFD) (Environment Agency, 2019). Each survey line ran further than the known extent of each bed to capture any changes to the bed extent since they were last surveyed. The survey lines were set up with 20 meter line spacing. Acoustic data was acquired using a MX Aquatic Habitat Echosounder (Appendix 2). The echosounder simultaneously acquires submerged aquatic vegetation (including seagrass), substrate and bathymetry data using Visual Acquisition by BioSonics (Version 6.4) software. The transducer was deployed over the port side of the vessel via a pole mounted on the side which can be deployed for survey operations. Acoustic data was collected in one survey area to map the extent of the bed. Remote access software was used on all laptops to enable the home based scientific officers to independently operate the MX Echosounder controls and HYPACK. Microsoft Teams was also used throughout each survey day to enable the home-based officers to maintain continuous communication with the survey crew aboard the vessel. On arrival at Cawsand, a Valeport Swift Sound Velocity Profiler was deployed to measure the Conductivity, Temperature, and Depth (CTD). Once recovered to deck the data was downloaded using Valeport Data log X2 software and the temperature and salinity values from the bottom depth were input into the Visual Acquisition software. A folder for the survey area was created prior to the deployment of the MX and data was recorded with date and time stamps for each file e.g. 20210823_113700. A target was created in HYPACK to indicate the start of line (SOL); this was repeated at the end of line (EOL). The speed over ground was aimed to be at a constant of 4.5 knots so that the pings from the MX were at a consistent distance. MX SOL and EOL positions, targets for verification and video tow SOL and EOL positions were recorded in the Lat/Long WGS84 projection taken from a single GPS, Hemisphere V500 GNSS system on Tiger Lily VI. HYPACK targets were extracted as a .txt file format and opened in Microsoft Excel (comma delimited). The video files and raw MX files (.dt4 and .rtpx) were transferred from the PC to a WD Passport for transport and storage at the end of each survey day. The log sheets were worked on from the shared network drive and saved at the end of each day. A total of 64 lines were completed and a total of 62 lines were included in the data analysis. All lines for each bed were loaded into Visual Aquatic by BioSonics software in a batch, then analysed individually. Quality assurance (QA) was carried out for tows individually and the bottom line and plant line were manually adjusted where there were errors. The plant line was adjusted when anything other than seagrass was present such as algae, noise in the water column when the vessel was turning and fish in the water column. Once each line was corrected, the post processing information was recorded in the survey log. The analysed data were exported from Visual Aquatic as a .csv file which records the data as an average of every ten pings. The data was copied to Microsoft Excel pasted to columns with corrected headers including latitude, longitude, date, time and notes. This was saved as a .xls file and imported into MapInfo Professional Advanced (Version 17.0.4) to create points. A theme was added to the points data for the plant height (m) and the plant coverage (%). A polygon was drawn around each survey area clipped to the point at the start and end of each tow. A raster was created using the natural neighbour function for plant height (m) and plant coverage (%). The settings for the raster were distance: 20 m, smoothing: 0, clipped to polygon for each survey area, cell size: user suggested and interpolated along edges. Advanced colour was used to define the colour scales. Plots were created for points of plant height (m), percentage cover (%) of seagrass, contour plot of plant height (m) and the contour plot of percentage cover of seagrass (%).