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Transitioning global change experiments on Southern Ocean phytoplankton from lab to field settings: insights and challenges

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Boyd, PW ORCID: 0000-0001-7850-1911, Doney, SC, Eggins, S, Ellwood, MJ, Fourquez, M, Nunn, BL, Strzepek, R ORCID: 0000-0002-6442-7121 and Timmins-Schiffman, E 2022 , 'Transitioning global change experiments on Southern Ocean phytoplankton from lab to field settings: insights and challenges' , Limnology and Oceanography , pp. 1-20 , doi: 10.1002/lno.12175.

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Abstract

The influence of global change on Southern Ocean productivity will have major ramifications for future management of polar life. A prior laboratory study investigated the response of a batch-cultured subantarctic diatom to projected change simulating conditions for 2100 (increased temperature/CO2/irradiance/iron; decreased macronutrients), showed a twofold higher chlorophyll-derived growth rate driven mainly by temperature and iron. We translated this design to the field to understand the phytoplankton community response, within a subantarctic foodweb, to 2100 conditions. A 7-d shipboard study utilizing 250-liter mesocosms was conducted in March 2016. The outcome mirrors lab-culture experiments, yielding twofold higher chlorophyll in the 2100 treatment relative to the control. This trend was also evident for intrinsic metrics including nutrient depletion. Unlike the lab-culture study, photosynthetic competence revealed a transient effect in the 2100 mesocosm, peaking on day 3 then declining. Metaproteomics revealed significant differences in protein profiles between treatments by day 7. The control proteome was enriched for photosynthetic processes (c.f. 2100) and exhibited iron-limitation signatures; the 2100 proteome exposed a shift in cellular energy production. Our findings of enhanced phytoplankton growth are comparable to model simulations, but underlying mechanisms (temperature, iron, and/or light) differ between experiments and models. Batch-culture approaches hinder cross-comparison of mesocosm findings to model simulations (the latter are akin to “continuous-culture chemostats”). However, chemostat techniques are problematic to use with mesocosms, as mesozooplankton will evade seawater flow-through, thereby accumulating. Thus, laboratory, field, and modeling approaches reveal challenges to be addressed to better understand how global change will alter Southern Ocean productivity.

Item Type: Article
Authors/Creators:Boyd, PW and Doney, SC and Eggins, S and Ellwood, MJ and Fourquez, M and Nunn, BL and Strzepek, R and Timmins-Schiffman, E
Keywords: global change, Southern Ocean, phytoplankton productivity, omics, physiology
Journal or Publication Title: Limnology and Oceanography
Publisher: Amer Soc Limnology Oceanography
ISSN: 0024-3590
DOI / ID Number: 10.1002/lno.12175
Copyright Information:

Copyright (2022) The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) License, (https://creativecommons.org/licenses/by-nc/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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