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1) The Atmocean wave pumps supplied for the OPPEX test were custom prototypes, not fully engineered ‘‘commercially available wave pumps.’’ 2) Winding the two sections of 150-m tubes onto the central coupler did not lead to ‘‘ease of deployment,’’ but rather induced twists in the tubes, which may have been a contributing cause of failure. 3) Attaching a coupler to the tube top of the single pump and one of the dual pumps was contrary to the design, and this led to the tube and center coupler failure because this shifted the structural element from the 3/80 steel cable to the plastic tube, producing an up-and-down exercising of weld joints of the center coupler. The design of the coupler included a vertical steel interconnected structure with attachment points for the upper cable and lower cable, thus providing a direct transfer of force between the buoy and the 315-m-deep valve. Instructions were to shorten the cable by ;5 m so that the bottom section of tube (between the center coupler and the valve) was longer than the cable. This was to maintain the upper and lower cables (and the vertical steel interconnect) as the sole structural element. The modifications cited by the authors did not ‘‘improve the chances of a successful experiment,’’ but rather guaranteed the eventual failure. 4) Video of the deployment showed that the ‘‘forward motion of the ship’’ caused the wound-up tube to rotate laterally rather than end-over-end, with each rotation inducing a twist in the plastic tube. As a general observation, deployment of tube-style pumps is best accomplished vertically and quickly (without ship involvement), not horizontally and slowly (using the ship forward motion to unwind the plastic tube). 5) On wave upslope, when the buoy and entire tube are moving upward, the top coupler (installed there by OPPEX, contrary to Atmocean design specifications) located just above the three-axis modular acoustic velocity sensor (MAV-3) may have ‘‘scooped’’ ambient water into the top of the tube, inducing intermittent downward flows that partly offset the upward flow. This would help explain the much lower rate of upwelling derived from the MAV-3 data. 6) Further explanation of the operating characteristics of this tube-style wave pump is necessary to evaluate the upwelling rate and calculated efficiency during the 17 h when pumping occurred. First, each valve flapper has a radius of 0.375 m and must rotate from the horizontal to vertical in order to close and open the valve. Therefore, a wave amplitude of 0.375 m is needed to trap water inside the valve and tube on each wave cycle. Second, with a calculated tube volume of 136 m, the mass of water inside the tube is 136 metric tons, which causes the cable to stretch on each wave upslope. However, the load limit is not the mass of water inside the tube, but the net buoyancy of the buoy, because in moderate wave conditions it partly submerges on each wave upslope, and in high or steep waves the buoy could completely submerge. The buoy used in OPPEX had a net buoyancy of Corresponding author address: Philip W. Kithil, 607 Cerrillos, Atmocean, Inc., Santa Fe, NM 87505. E-mail: atmocean.kithil@gmail.com JUNE 2011 C O R R E S P O N D E N C E 847

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