Equipment must be appropriately set-up and described to ensure as much consistency as possible among surveys and to facilitate gear replacement if necessary. The overarching goal of appropriately choosing and setting up equipment is to sample as much of the sediment as possible with minimal disruption, within the limitations of the given equipment. It is recommended that a survey include at least two gear types to sample sediments, one targeted for finer sediment (muds) and the other targeted for sands and coarser sediments (gravel). Researchers should ensure appropriate statistical tests are performed to test for potential confounding factors of gear type on biological variables (e.g. Pennington et al. 1998, Souza and Barros 2015), particularly regarding penetration depth and substrate type.
The key components for a grab include the following, all of which should be documented:
- Type of grab, including firing mechanism (e.g. Van Veen, Smith-McIntyre, Shipek);
- Weight of grab;
- Bucket dimensions (surface area sampled, shape, maximum volume);
- Maximum penetration into the substrate;
- Trap door to allow examination of sample volume upon recovery and to allow sediment sampling from the relative undisturbed centre. Most grab designs can have this feature, but not all manufacturers include it;
- Additional weights (by providing an option for extra attached weights to a grab or corer, equipment functionality can be optimised among more habitat types); and
- Standard electronics to be used (e.g. GPS, camera, USBL, vessel sounder).
The key components for a corer include the following, all of which should be documented:
- Type of corer (e.g. box, multicorer);
- Weight of corer;
- Surface area of sample;
- Maximum volume of sample;
- Additional weights (by providing an option for extra attached weights to a grab or corer, equipment functionality can be optimised among more habitat types); and
- Standard electronics to be used (e.g. GPS, camera, USBL, vessel sounder).
Grabs and box corers can also be fitted with other sampling platforms and sensors. A mounted video camera can add valuable information about the _in situ _appearance of the seabed that is sampled including opportunistic imagery of biota, as well as an indication of the performance of the gear (Blomqvist 1991). Similarly, conductivity-temperature-depth (CTD) meters and other sensors provide information about the surrounding environment, while a pinger (i.e. near-bottom echosounder) provides information to the operator about distance to the seafloor which can be very important for controlling the final operation near the seafloor (Narayanaswamy et al. 2016).