Metadata Report for BODC Series Reference Number 2012113

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

Kongsberg EM120 Multibeam Echosounder

The EM120 is a low frequency (12 kHz) multibeam echosounder with full ocean depth capability designed for bathymetric surveys. It measures water depth by monitoring the travel time of an acoustic signal that is transmitted from the ship, reflected off the seabed and received back at the ship.

The main system units of the EM120 are transducer arrays (separate for reception and transmission), preamplifier unit, transceiver unit and operator unit. Sub-bottom profiling capability is an optional extra. For both transmit and receive arrays standard beamwidth is 1° or 2°, and 4° beamwidth is available for the receive array.

The system has 191 beams with pointing angles automatically adjusted according to achievable coverage or operator defined limits. The beam spacing is normally equidistant, corresponding to 1% of depth at 90° angular coverage, 2% at 120° and 3% at 140°. The transmit fan is split into several individual sectors, each of which is corrected independently for vessel roll, pitch and yaw, which places all soundings on a "best fit" to a line perpendicular to the survey line.

The EM120 supersedes the EM12 and was itself superseded by the EM122 in 2008.

Specifications

Further details can be found in the manufacturer's specification sheet.

RRS James Cook JC136 navigation instrumentation

The following scientific navigational and bathymetric systems were fitted:

Trimble Applanix Position and Orientation Systems for Marine Vessels (POSMV)

The Position and Orientation Systems for Marine Vessels (POSMV) is a real time kinematic (RTK) and differential global positioning system (DGPS) receiver for marine navigation. It includes an inertial system that provides platform attitude information. The instrument provides accurate location, heading, velocity, attitude, heave, acceleration and angular rate measurements.

There are three models of Applanix POSMV, the POS MV 320, POS MV Elite and the POS MV WaveMaster. POS MV 320 and POS MV WaveMaster are designed for use with multibeam sonar systems, enabling adherence to IHO (International Hydrographic Survey) standards on sonar swath widths of greater than ± 75 degrees under all dynamic conditions. The POS MV Elite offers true heading accuracy without the need for dual GPS installation and has the highest degree of accuracy in motion measurement for marine applications.

Specifications

POS MV 320

POS MV WaveMaster

POS MV Elite

¹ One Sigma, depending on quality of differential corrections
² Whichever is greater, for periods of 20 seconds or less

Further details can be found in the manufacturer's specification sheet.

RRS James Cook JC136 navigation data processing procedures

Originator's Data Processing

The data were logged by the TECHSAS (TECHnical and Scientific sensors Acquisition System) system into daily NetCDF files. The TECHSAS system is used as the main data logging system on NMF-SS operated reserach vessels. The daily TECHSAS NetCDF navigation and bathymetry files provided to BODC were used for BODC processing. Data were additionally logged into the RVS Level-C format files which have been archived at BODC. A portion of the data were then processed daily using the National Oceanography Centre MSTAR data procesing routines (mstar_version_v3).

Files delivered to BODC

BODC data processing

The data were reformatted to BODC internal format using standard banking procedures. Data were averaged at 60 second intervals. The following table shows how variables within the file were mapped to appropriate BODC parameter codes:

*-*-position-Applanix_GPS_JC1.gps

*-*-gyro-GYRO1_JC1.gyr

*-*-sb_depth-EM120_JC1.depth

*-*-EA600-EA600_JC1.EA600

Processing

All the reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag.

A check was run on positional data to identify gaps and improbable values (through the calculation of speed where speed is >10 m/s). No issues were detected.

GEBCO bathymetry (15 second grid) was added to the file using the main latitude and longitude channels. It was used to screen echo-sounder bathymetry.

Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the file, using BODC standard procedures.

The single-beam echo-sounder data was affected by a strong variability and large amount of spikes. The noisy data were flagged appropriately in Edserplo. Bathymetry data were filtered of noise twice by applying a moving median window of 30 secs and removing all data outside 1 standard deviation

Project Information

Deep Links: Influence of population connectivity on depth-dependent diversity of deep-sea marine benthic biota

Background

Species populations are connected to each other through both movement of adults (migration) and eggs, larvae and juveniles (dispersal). If populations become isolated from one another (i.e. are no longer connected), then through genetic mutation, drift and natural selection, they may become so different that they evolve into new biological species. Understanding how populations become isolated is critical to understanding the process of speciation. In the marine environment many species do not move as adults (e.g. corals) or move very slowly (sea urchins). This means that for different adult populations to remain connected they rely on dispersal of early life history stages. Most marine species have a larval stage that lives in the plankton for a period of time, moving with the currents, before settling in a new area. It is larval dispersal that keeps distant populations connected. So understanding patterns of larval dispersal is important to understanding connectivity.

In the deep-sea (>200m) the bathyal region of the continental slope has been identified as supporting high species richness and being an area where the rate of origination of new species may also be high. The reasons for this are not clear, but given the importance of connectivity to population isolation and speciation, it follows that the key to understanding patterns of species diversity in this region lies in understanding connectivity. New research has suggested that because the speed of the currents that carry larvae decreases as you go deeper, larvae might not be able to travel as far, leading to a greater tendency for populations at bathyal depths to become isolated over a given distance, and thus increasing the chances of speciation.

This study aims to test this theory by investigating how patterns of connectivity vary with depth. This will be done in 3 ways:

1. Using genetic analysis (similar to DNA fingerprinting) to compare how related distant populations are and if they become less closely related as you go deeper
2. Using a model of ocean currents to simulate the movement of larvae between sites
3. Io look at the range and abundance of species present at distant locations to see if those at shallower depths are more similar to each-other than those at bathyal depths.

Fieldwork

Data were collected on James Cook cruise JC136 between 14^th May and 23^rd June 2016. During the cruise, 5 sites in the North East Atlantic (Rockall Bank, George Bligh Bank, Anton Dohrn Seamount, Wyville-Thomson Ridge, and Rosemary Bank) were visited undertaking 27 ROV dives, 12 AUV missions, 43 CTD casts, 2 mooring deployments. 3630 biological samples were obtained from sufficient depth and site coverage for molecular analysis for 3 target species.

Participants

• Dr Kerry Howell (Principal Investigator - Parent Grant) University of Plymouth
• Dr Andy Foggo (Co-Investigator) University of Plymouth
• Dr Alex Nimmo-Smith (Co-Investigator) University of Plymouth
• Dr Vasyl Vlasenko (Co-Investigator) University of Plymouth
• Professor Alex Rogers (Principal Investigator - Child Grant) University of Oxford

Funding

This project was funded by Natural Environment Research Council parent and child grants NE/K011855/1 and NE/K013513/1, entitled 'Influence of population connectivity on depth-dependent diversity of deep-sea marine benthic biota', with the former, parent grant led by Dr Kerry Howell, University of Plymouth, and the latter child grant led by Professor Alex Rogers, University of Oxford. The project was also in partnership with the Joint Nature Conservation Committee (JNCC) and the British Geological Survey (BGS). The project was active between 16^th November 2015 and 31^st December 2019.

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: