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Ocean acidification reduces the growth of two Southern Ocean phytoplankton

journal contribution
posted on 2023-05-21, 09:13 authored by Andrew, SM, Robert StrzepekRobert Strzepek, Branson, O, Ellwood, MJ
Model projections for the Southern Ocean indicate that light, iron (Fe) availability, temperature and carbon dioxide (CO2) will change concurrently in the future. We investigated the physiological responses of Southern Ocean phytoplankton to multiple variables by culturing the haptophyte Phaeocystis antarctica and the diatom Chaetoceros flexuosus under various combinations of light, Fe, temperature and CO2. Using statistical models, the influence of each environmental variable was analysed for each physiological response, ultimately predicting how ‘future’ conditions (high temperature and high CO2) would influence the 2 phytoplankton species. Under future conditions, cellular chlorophyll a and carbon to nitrogen molar ratios were modelled to increase for both species in all light and Fe treatments, but at times were inconsistent with measured values. Measured and modelled values of the photochemical efficiency of photosystem II (Fv/Fm) declined in cultures of P. antarctica due to concurrent increases in temperature and CO2, under all light and Fe treatments. The trends in Fv/Fm for C. flexuosus were less clear. Our model and observations suggest that when temperature and CO2 are concurrently increased, the growth of both species remains largely unchanged. This modelling analysis reveals that high CO2 exerts a strong negative influence on the growth of both phytoplankton, and any ‘future’ increase in growth can be attributed to the positive effect of warming rather than a CO2 fertilisation effect.

History

Publication title

Marine Ecology Progress Series

Volume

682

Pagination

51-64

ISSN

0171-8630

Department/School

Institute for Marine and Antarctic Studies

Publisher

Inter-Research

Place of publication

Nordbunte 23, Oldendorf Luhe, Germany, D-21385

Rights statement

Copyright (2022) Inter-Research

Repository Status

  • Restricted

Socio-economic Objectives

Antarctic and Southern Ocean oceanic processes; Expanding knowledge in the biological sciences; Expanding knowledge in the environmental sciences

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