Preprints
https://doi.org/10.5194/essd-2021-351
https://doi.org/10.5194/essd-2021-351

  09 Nov 2021

09 Nov 2021

Review status: this preprint is currently under review for the journal ESSD.

Primary productivity measurements in the Ross Sea, Antarctica: A regional synthesis

Walker O. Smith Jr.1,2 Walker O. Smith Jr.
  • 1School of Oceanography, Shanghai Jiao Tong University, Shanghai, 200400, PRC
  • 2Virinia Institute of Marine Science, William & Mary, Gloucester Pt., VA, 23062, USA

Abstract. Polar systems are undersampled due to the difficulty of sampling remote and challenging environments; however, these systems are critical components of global biogeochemical cycles. Measurements on primary productivity in specific areas can quantify the input of organic matter to food webs, and so are of critical ecological importance as well. However, long-term measurements using the same methodology are available only for a few polar systems. Primary productivity measurements using 14C-uptake incubations from the Ross Sea, Antarctica, are synthesized, along with chlorophyll concentrations at the same depths and locations. A total of 19 independent cruises were completed, and 449 stations occupied where measurements of primary productivity (each with 7 depths) were completed. The incubations used the same basic simulated in situ methodology for all. Integrated water column productivity for all stations averaged 1.10 ± 1.20 g C m−2 d−1, and the maximum was 13.1 g C m−2 d−1. Annual productivity calculated from the means throughout the growing season equalled 146 g C m−2 yr−1. Mean chlorophyll concentration in the euphotic zone (the 1 % irradiance level) was 2.85 ± 2.68 mg m−3 (maximum concentration was 19.1 mg m−3). Maximum photosynthetic rates at the surface (normalized to chlorophyll) averaged 0.94 ± 0.71 mg C (mg chl)−1 h−1, similar to the maximum rate found in photosynthesis/irradiance measurements. Productivity measurements are consistent with the temporal patterns of biomass found previously, with biomass and productivity peaking in late December; mixed layers were at a minimum at this time as well. Estimates of plankton composition also suggest that pre-January productivity was largely driven by the haptophyte Phaeocystis antarctica, and summer productivity by diatoms. The data set will be useful for a comparison to other Antarctic regions and provide a basis for refined bio-optical models of regional primary productivity.

Walker O. Smith Jr.

Status: open (until 04 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2021-351', Anonymous Referee #1, 17 Nov 2021 reply
    • AC1: 'Reply on RC1', walker smith, 02 Dec 2021 reply

Walker O. Smith Jr.

Data sets

Ross Sea primary productivity description Walker Smith https://www.bco-dmo.org/dataset/863815

Ross Sea primary productivity Walker Smith https://www.bco-dmo.org/dataset/863815/data

Walker O. Smith Jr.

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Short summary
The rate of photosynthesis of marine phytoplankton – primary productivity – is typically measured by quantifying the rate of radioisotope incorporation. However, generally such measurements are not collected by one individual through time, so are difficult to compare due to methodological differences. A data set compiled by one investigator over more than 20 years in the Ross Sea demonstrates the importance of the region as a "hot spot" for growth and synthesis.