Dataset: PICO biogeochemical data collected from Duke Marine Lab dock from 2011-2022

Water was sampled at ~10:30am local from a dock using a 5 L niskin bottle centered at 1 m with a bottle length of 0.7 m.  Subsamples were processed immediately following water collection.

DIC

DIC was measured on mercuric chloride poisoned samples by acidification and subsequent quantification of released CO₂ using a CO₂ detector (Li-Cor 7000). DIC samples were collected following recommended procedures {Dickson et al., 2007} and measurements were calibrated against Certified Reference Materials provided by Dr. A. G. Dickson at Scripps Institution of Oceanography (SIO), University of California, San Diego (UCSD).

Dickson, A.G., Sabine, C.L., and Christian, J.R. (eds) (2007) Guide to best practices for ocean CO₂ measurements: PICES Special Publication 3.

Chlorophyll

Methods described in Johnson et al. 2010: Chlorophyll concentrations were measured by filtering 25  mL of seawater sample onto a 0.22 µm pore size polycarbonate filter using gentle vacuum (<100 mm Hg) and extracting in 100% MeOH at -20°C in the dark for >24 h following (Holm-Hansen and Riemann, 1978).  Fluorescence was measured using a Turner Designs 10-AU fluorometer following (Welschmeyer, 1994) that was calibrated against a standard chlorophyll solution (Ritchie, 2006).

Johnson, Z.I., Shyam, R., Ritchie, A.E., Lin, Y., Mioni, C., Lance, V.P. et al. (2010) The effects of iron- and light-limitation on phytoplankton communities of deep chlorophyll maxima of the Western Pacific Ocean. Journal of Marine Research 68: 1-26.

Holm-Hansen, O., and Riemann, B. (1978) Chlorophyll a determination: Improvements in methodology. Oikos 30: 438-447.

Welschmeyer, N.A. (1994) Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments. Limnology and Oceanography 39: 1985-1992.

 Ritchie, R. (2008) Universal chlorophyll equations for estimating chlorophylls a, b, c , and d and total chlorophylls in natural assemblages of photosynthetic organisms using acetone, methanol, or ethanol solvents. Photosynthetica 46: 115-126.

Secchi Depth

Secchi depth was measured in duplicate using a 20 cm disk with four alternating white and black quadrants by lowering the disk until no longer visible and recording the depth.

Salinity

Salinity was measured using a calibrated handheld digital refractometer (Atago PAL-06S), using a refractometer (Vista A366ATC), YSI Pro30, YSI ProODO, YSI ProSolo or using a Guideline Portasal 8410A all according to manufacturer’s instructions and calibrated against known reference materials.

Turbidity

Turbidity reported in Nephelometric Turbidity Units [NTU]  was measured in duplicate on discrete samples using a calibrated handheld turbidimeter (Orion AQ4500) according to manufacturer’s instructions.

Temperature

Temperature was measured in duplicate using NIST traceable thermocouples (VWR#23609-232) from bottle water or from in situ probes YSI Pro30, YSI ProODO or YSI ProSolo according to manufacturer’s instructions.

pH

pH was measured spectrophotometrically (Clayton and Byrne, 1993) in triplicate at standard temperature (25 degrees C) immediately following collection. pH samples were collected following recommended procedures (Dickson et al., 2007).

Clayton, T.D., and Byrne, R.H. 1993. Spectrophotometric seawater pH measurements: total hydrogen ion concentration scale calibration of m-cresol purple and at-sea results. Deep Sea Research Part I: Oceanographic Research Papers 40: 2115-2129. doi: 10.1016/0967-0637(93)90048-8

Dickson, A.G., Sabine, C.L., and Christian, J.R. (eds). 2007. Guide to best practices for ocean CO2 measurements: PICES Special Publication 3.

Bacteria, Synechococcus, picocyanobacteria, pico-photosynthetic eukaryotes

Bacterioplankton (“bacteria”, DNA containing, non-red fluorescing populations), Synechococcus (small, red and orange fluorescing populations),  “picocyanobacteria” (small, red fluorescing populations; includes Prochlorococcus and ‘green’ Synechococcus), and “picoeukaryotes” (DNA containing, red and orange fluorescing populations) were measured flow cytometrically as previously described (Johnson et al., 2010) using a BD FACSCalibur, or using Hoechst 34580 or Sybr Green I DNA stains using an Attune NxT with 405 nm excitation and 440±25, 512±13, 603±24, 710±25 nm emission and 488 nm excitation and 530±15, 574±13, 695±20, 780±30 nm emission as previously described (Selph 2021)

Johnson, Z.I., Shyam, R., Ritchie, A.E., Lin, Y., Mioni, C., Lance, V.P. et al. (2010) The effects of iron- and light-limitation on phytoplankton communities of deep chlorophyll maxima of the Western Pacific Ocean. Journal of Marine Research 68: 1-26.

Selph KE Enumeration of marine microbial organisms by flow cytometry using near-UV excitation of Hoechst 34580-stained DNA. Limnol Oceanogr Methods 19: 692-701.

Inorganic Nutrients (NH4, NO3, SiOH4)

Water was filtered through a 0.22 um Sterivex cartridge filter, Millipore #SVGPL10RC using a peristaltic pump input line at 1 m for later nutrient analysis (NO3, NH4, SiOH4). Water was sampled in duplicate into HCl-cleaned HDPE bottles (VWR#414004-110) and stored at -80 degrees C until later analysis using an Astoria-Pacific A2 autoanalyzer (NO3 and SiOH4), following the manufacturer’s recommended protocols by running each replicate sample in duplicate. NH4 was measured in triplicate following Holmes et al. 1999 using a Turner 10-AU fluorometer. For some time points inorganic nutrients were processed by the Scripps Institute of Oceanography STS/ODF chemistry laboratory

Certified reference materials were used to verify protocols (Inorganic Ventures: QCP-NT, QCP-NUT-1, CGSI1-1). The detection limits were: NO2 = 0.05 uM, NO3 = 0.1 uM, PO4 = 0.05 uM, SiOH4 = 0.2 uM. Values measured below these limits are reported as zero.

Production and Respiration

Production and respiration quantified using Winkler oxygen (Labasque et al., 2004) were measured using the light/dark bottle technique with 24 h incubations at ambient temperature in a sinusoidal incubator (Sanyo MLR-351H) with ~1000 µmol quanta m^-2 sec^-1 peak PAR.