Retrieval

Important considerations:

In order to avoid losing organisms during the recovery phase, we enclose the ARMS in a box or a mesh-lined milk crate before any disturbance. Once the ARMS and contents are secured, it can then be lifted off the sea floor.

The ARMS should be turned upside-down when lifted out of the water to keep the organisms in the plate stack and placed immediately in a tub filled with filtered seawater and aerated.

Processing should be done as soon as possible. If it is not possible to process the ARMS soon after retrieval, the unit should be left in the water tub in a cool place.

Materials:

  • 1 clean recovery crate (milk crate) lined with 100-micron nytex mesh
  • 2 hooked elastic cords (bungee cords)
  • 1 battery operated bubbler with tubing and air stone
  • gloves that cover up to the elbow - industrial dish gloves work well and can be reused if cleaned
  • 1 hammer
  • 1 chisel
  • Zip ties
  • 1 dive knife or dive scissors
  • 1 tub big enough to contain the ARMS with lid (before and between uses, this tub must be cleaned with 10% bleach and rinsed thoroughly)
  • 1 clean bucket
  • 1 40-microns plankton net
  • Optional: water pump

Procedures:

  1. On the boat or shore, fill the clean tub with filtered sea water using the bucket (or water pump) and the plankton net. Be careful not to touch the water with bare hands to avoid introducing exogenous DNA.
  2. Place the operating bubbler in the water
  3. Underwater, take photographs of the ARMS and surroundings before retrieval
  4. To orientate the ARMS, you can mark a corner of the ARMS facing the direction of your choice using a zip tie - note the orientation.
  5. Carefully place the mesh-lined milk crate on top of the ARMS, making sure to not disturb the communities living inside the unit
  6. If organism growths prevent you from securely attaching the crate, you can carefully trim the organisms with the dive knife
  7. Secure the milk crate with the bungee cords
  8. Remove the anchoring system
  9. Carefully bring the ARMS back to the surface, invert the unit so that the base plate is facing upwards. The ARMS and milk crate are very heavy - multiple individuals in a coordinated effort are required to avoid injury.  Lift the ARMS out of the water. Water will drain off the unit through the mesh so that no animals will escape.
  10. Place the unit immediately in the aerated water tub. Ensure that all the ARMS layers are submerged. Process the ARMS unit as soon as possible.

Illustrations:

Preparation of the recovery bin where the retrieved ARMS will be placed. Filtering seawater through a 45-μm mesh.

Securing the crate on top of the ARMS with bungee cords. Removing the anchors to retrieve the unit.

The ARMS is lifted upside down out of the water and placed in the recovery bin with the filtered seawater. Bubblers are added for oxygenation.

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