Water samples from 7 depths spanning the euphotic zone were collected using a CTD-rosette during the 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). Depths varied according to experimental cycle, as it was adjusted based on photosynthetically active radiation (PAR) profiles to span the depth to 0.1% of surface irradiance. The physiology of the phytoplankton community was evaluated using the Mini-Fire fast repetition rate fluorometer (FRRF), using approximately 5ml per depth. Fv/Fm and reoxidation of Qa-, the first quinone acceptor of PSII, were evaluated using the Mini-Fire FRRF, which provided indications of phytoplankton stress most likely caused by iron-limitation following the procedure outlined in Gorbunov and Falkowski (2020 doi:10.1002/lno.11581).

Empty cells = ndThis 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.