Zooplankton Pump Procedure for Broadscale and Process Cruises

General

The target depths are >40, 15-40, and 0-15 m. The plankton pump hose is retrieved at a constant rate changing nets at the appropriate depths to provide integrated samples over each depth range. The goal is to filter a volume of 0.5 m3 over each 5 m depth range. Since the pump flow rate varies according to suction hose length (385 l min-1 with three 100 ft sections of suction hose and 530 l min-1 with two sections) the retrieval rate varies. For 2 sections of hose the retrieval rate is 5 m min-1, while for 3 sections of hose the retrieval rate is 3.8 m min-1. Also it is necessary to allow water to clear the hose before collecting a sample and the procedures below provide for this.

Procedure

Before starting, make sure that the starboard side of the ship is facing upwind so that the hose will drift away from the ship.
  1. Make sure the pump is full of gas

  2. Connect up the hoses, and prime the pump with seawater using the deck seawater hose. Make sure that the black suction hose is the one which goes over the side of the ship. Attach hose intake to the CTD.

  3. Lower CTD and hose to the bottom depth or to within 5m of the bottom. If depth is less than 60 m use only 2 sections of hose. If greater use three sections. Even at shallow depths make sure all the hose is out (it is much easier to prime the pump when there is only a short section of hose with air in it on the deck). When lowering hose with the CTD keep a little tension on it. Have suction hose tied off between where it goes over the side and the pump to take the strain off the pump.

  4. Start the pump and allow the hose to fill. Fill tank with water then open valve at base of manifold to divert the water over the side. Place net over tank. Note: Do not ever close both the valve which lets the water into the net and the one which diverts the water over the side. Doing this will deadhead the pump and the pressure will burst the hose.

    5. For two sections of intake hose.

  5. Start raising the hose at 5 m min-1 from the bottom depth.

  6. After 40 secs (the time taken for water to pass through the hose), take the flow meter reading and start filtering water by opening the valve leading to the net and then closing the diversion valve.

  7. When the hose intake is at 37.5 m switch nets and record the volume filtered.

  8. When the hose intake is at 12.5 m switch nets and record the volume

  9. When the hose intake reaches the surface continue to filter water for an extra 30 secs. Then stop and record the volume. Go to step 15.

    10. For three sections of hose

  10. Start raising the hose at 4 m min-1 from the bottom depth.

  11. After 60 secs (the time taken for water to pass through the hose), take the flow meter reading and start filtering water by opening the valve leading to the net and then closing the diversion valve.

  12. When the hose intake is at 36 m switch nets and record the volume filtered.

  13. When the hose intake is at 11 m switch nets and record the volume.

  14. When the hose intake reaches the surface continue to filter water for an extra 60 secs. Then stop and record the volume.

    15. After completing the sampling

  15. Raise the CTD out of the water and pump the suction hose dry (this makes retrieval of the hose easier. Slow pump engine down then turn off the motor. Turn off flow meter.

  16. Undo the hose from suction side of the pump to release vacuum and retrieve hose laying it out in long loops on the starboard rail. Bring CTD on board and secure. Remove intake hose from the CTD. Undo other hoses and put away with suction hose. Secure all hoses, cover pump and secure cover with strap. Drain tank holding nets.

  17. Rinse the nets into the cod ends. Open the cod ends in small numbered buckets (1=bottom net etc) and rinse the contents of the cod end into the bucket. Filter the samples onto a 40 um screen and then rinse the sample into 8 oz jars for preserving. Preserve with borate buffered formalin.

    18. Prepared by: Ted Durbin 5/26/95