ALBERT

Description: Biomass accumulation was assessed by subtracting phytoplankton mortality (due to microzooplankton) from phytoplankton growth rates. Rates of phytoplankton growth and microzooplankton grazing were assessed daily with the dilution technique (Landry and Hassett 1982; doi:10.1007/BF00397668), following the two treatment approach (Landry, Haas et al. 1984 doi:10.3354/meps016127), at six depths within the euphotic zone. We implemented this mini-dilution approach to generate vertically resolved growth and grazing rates, but also conducted a full dilution experiment on the last day of each of the cycles (n = 5) to test linearity assumptions of the method. Seawater collected with the Niskin bottles attached to the CTD rosette at 02:00 h was used to fill a pair of 2.2-L polycarbonate bottles (100%, B and C) while a third bottle (A) was filled with 25% whole seawater diluted with 0.2-µm filtered seawater obtained immediately before by gravity filtration using an Acropak filter cartridge (Pall) directly from the same Niskin bottle. Nutrients (final concentrations in 2.2L bottles; nitrate 0.18 μM, ammonium 4.16 μM, phosphate 15.08, silicate 44.2 μM, and vitamins) were added to bottles A and B in order to ensure the assumption that the same phytoplankton intrinsic growth rate was occurring in WSW and FSW bottles despite dilution (Gutiérrez‐Rodríguez, Safi et al. 2020 doi:10.1029/2019JC015550). Bottles were then incubated in situ at the same six depths of collection using a drifting array. Rates were calculated from changes in Chl a concentration and picophytoplankton abundance between the beginning and end of the experiment assuming exponential growth of phytoplankton. Microzooplankton grazing rate was estimated from: µ = (kA – kB)/(1-x) where kA and kB are the observed net rates of change of chl a in bottles A and B, respectively, and x is the fraction of whole seawater in the diluted bottle A (0.25). Phytoplankton growth rate was estimated from µ =m+kB. Photoacclimation effects were corrected from changes in cell chl a fluorescence estimated by flow cytometry during incubations as a proxy of cell chl a content (Gutierrez-Rodriguez, Latasa et al. 2010 doi:10.1016/j.dsr.2009.12.013). These include estimating the photoacclimation index (Phi) from changes in FL3: FSC and calculating an average value from Phi index obtained for pico- and nanoeukaryotic populations weighted by their biomass contribution. Accumulation was calculated by subtracting the C-based estimates of microzooplankton grazing (from the dilution experiments) from the 14C-based NPP.

Description: Salps were collected using double oblique Bongo tows, with 0.7m diameter frames equipped with 202 µm nets, General Oceanics flow meters, and an RBR temperature depth recorder. Salp specimens (typically 10) from each tow had their guts excised, and chl a and phaeopigments gut contents were measured. A power function was used to fit the size-specific Gpig (chl a + phaeo) contents for each tow, allowing the estimation of Gpig for each size bin per tow, and this was multiplied by the abundance in each size bin. Gut passage time (GPT) was calculated using a modified equation, based on (von Harbou, Dubischar et al. 2011 doi:10.1007/s00227-011-1709-4) where GPT(h) = 2.607*ln(OAL, mm) - 2.6. Grazing was estimated as: G (h-1) = Gpig /GPT, and scaled using a Q10=2. Daily salp grazing rates were obtained by assuming 14 h of day and 10 h of night, coincident with the times and latitudes at which we sampled these communities during the Salp Particle expOrt and Ocean Production (SalpPOOP) campaign. Cycle estimates were calculated by first averaging all day and all night tows separately, and then adding the two estimates. Fecal pellet production was calculated by assuming an egestion efficiency of 0.36 (Huntley, Sykes et al. 1989 doi:10.1007/BF00238291, Pakhomov 2004 doi:10.1016/j.dsr2.2001.03.001, Pakhomov and Froneman 2004 10.1016/j.dsr2.2000.11.002) and converting to carbon values using C:Chl ratios from the phytoplankton growth and grazing experiments combined with NPP, and reported in mg C m-2 d-1. Data is reported by size after binning in 5mm size bins (ranging 1-135mm), and for oozooids and blastozooids separately.

Description: 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).

Description: Phytoplankton community composition was assessed using chemotaxonomic pigments (including all chlorophyll types, accessory and photoprotective pigments) measured with high performance liquid chromatography (HPLC). 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 PAR profiles to span the depth to 0.1% of surface irradiance. Chemotaxonomic pigments of phytoplankton in the water column were filtered onto GF/F filters (2L), then immediately flash-frozen in liquid nitrogen, and shipped frozen to Instituto Español de Oceanografía, Centro Oceanográfico de Gijón, where they were extracted for High-performance liquid chromatography (HPLC) analyses following established protocols (doi:10.4319/lom.2014.12.46). For this study, 2 profiles from each experimental cycle were analyzed, and vertically integrated to obtain areal estimates for each cycle. Pigment contributions were normalized by total chlorophyll a (Chl a) to account for potential losses and low yield, and are thus presented as integrated percentages per cycle. These proportions do not always sum to 100 because ancillary pigments/other compounds that cannot be positively identified are not included.

Description: 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).

Description: Here we present physico-chemical data collected during two research cruises conducted to and across the Ross Sea, Antarctica in the summer of 2018 (February-March) and 2019 (January-February). The dataset includes measurements of temperature, salinity, oxygen, par and transmissivity obtained with a Sea-Bird Electronics (SBE) 911plus CTD. The CTD sensor was configured with SBE 3plus, SBE 4, and SBE 43 dual sensors for the parameters above, in addition to a seapoint fluorescence sensor, and a photosynthetically active radiation (PAR) sensor (Biospherical Instruments QCP‐2300L‐HP). These data were used to provide oceanographic context to DNA metabarcoding analysis of 18S rRNA V4 region that was carried out on DNA samples collected in parallel to nutrient and chlorophyll-a samples. Fastq samples from DNA metabarcoding analysis and the associated metadata (including nutrients, Chlorophyll-a, and size-fractionated chlorophyll-a) were deposited to GenBank under project numbers PRJNA756172 (2018 cruise) and PRJNA974160 (2019 cruise). The study resulting from this analysis has been submitted to Limnology and Oceanography.

Description: Here we present data of phytoplankton pigment and flow cytometry (FCM) data in the water column (CTD_HPLC_FCM_May2022.xlsx) and dilution grazing experiments (DILEX_HPLC_FCM_Conc_May2022.xlsx), and derived apparent growth rates for specific pigment markers and picophytoplankton groups assessed by FCM (APPARENT_GROWTHRATES_May2022.xlsx). Samples and experiments were collected and carried out in subantarctic waters across the Campbell Plateau region southeast of New Zealand. We distinguish between a subset of 'Experimental' stations (n = 8), where serial dilution experiments were conducted and a subset of additional 'Biomass' stations (n = 7), where depth-resolved physico-chemical and biological measurements (e.g., nutrients, size-fractionated chlorophyll a (SF-Chla), optical microscopy, FCM and HPLC) were also undertaken throughout the euphotic zone. 'Experimental' stations were used to characterize phytoplankton group-specific growth and grazing rates and associated carbon production and microzooplankton consumption dynamics in surface-mixed layer waters (10 m) On-plateau (n = 5) and Off-plateau (n = 3) with 'Biomass' stations providing a broader context of the environmental conditions and phytoplankton biomass and taxonomic composition across the region.

Description: The present data set provides context to 653 samples (including 4 size fractions, 0.8-5 µm, 5-20 µm, 20-180 µm and 180-2000 µm) collected in the [SRF] surface water layer (ENVO:00010504) and the [DCM] deep chlorophyll maximum layer (ENVO:01000326) at 113 sampling stations during the Tara Oceans expedition. The present data set also provides links to the corresponding nucleotides data at the European Nucleotides Archive and the abundance of metabarcodes and OTUs for Rhizaria and Collodaria from the 113 sampling stations. Additional context can be found in the related publications and source data sets.