Sampling Larvae in Pumps
We used high-volume water samplers (McLane WTS-LV) to collect larvae of vent species and other plankton near the ridge. The samplers were equipped with 50-L pump heads, and 63 mm mesh filters. Pumps were deployed on pairs of moorings during LADDER-1 and LADDER-2 cruises. On LADDER-1, one mooring of each pair was located within the axial trough near an active, colonized vent and the other roughly 100 m off axis to the east. On LADDER-2, the second mooring was located within the axial trough, but at least 100 m away from active vents. On each mooring, the lower pump was positioned at 3 m above bottom (mab), and the upper pump at 75 mab, roughly the height of the neutrally buoyant plume (except at K vent where the plume was higher, and the upper pump positioned at 139 mab). The pumps typically sampled for 24 hrs, resulting in sample volumes of ~40,000 L.