Water collection for nutrient analysis was done using a CTD rosette equipped with 24 10L Niskin bottles, at different depths throughout the water column depending on the cast, spanning the euphotic zone to a maximum depth of 200m. Multiple casts were done during five Lagrangian experimental cycles conducted during Salp Particle expOrt and Ocean Production (SalpPOOP), from October to November 2018 in the vicinity of the Chatham Rise (New Zealand). Water was filtered through 25mm Whatman GF/F filters onto clean polyethylene bottles (250ml) and frozen at -20 °C. Analysis was done at the NIWA Hamilton Water Quality Laboratory (New Zealand), using an Astoria Pacific API 300 microsegmented flow analyzer (Astoria-Pacific, Clackamas, OR, United States) following colorimetric the methods outlined in Law et al. (2011; doi:10.1016/j.dsr2.2010.10.018).

This study was funded by the Ministry for Business, Innovation and Employment (MBIE) of New Zealand, NIWA core programmes Coast and Oceans Food Webs (COES- COES1901) and Ocean Flows (COOF-COOF1902), the Royal Society of New Zealand Marsden Fast-track award to Moira Décima, and NSF award #OCE-1756610 to Michael R. Stukel and Karen E. Selph.