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Seawater pH, and not inorganic nitrogen source, affects pH at the blade surface of Macrocystis pyrifera: implications for responses of the giant kelp to future oceanic conditions

Citation

Fernandez, PA and Roleda, M and Leal, PP and Hurd, CL, Seawater pH, and not inorganic nitrogen source, affects pH at the blade surface of Macrocystis pyrifera: implications for responses of the giant kelp to future oceanic conditions, Physiologia Plantarum, 159, (1) pp. 107-119. ISSN 0031-9317 (2016) [Refereed Article]

Copyright Statement

Copyright 2016 Scandinavian Plant Physiology Society

DOI: doi:10.1111/ppl.12478

Abstract

Ocean acidification (OA), the ongoing decline in seawater pH, is predicted to have wide-ranging effects on marine organisms and ecosystems. For seaweeds, the pH at the thallus surface, within the diffusion boundary layer (DBL), is one of the factors controlling their response to OA. Surface pH is controlled by both the pH of the bulk seawater and by the seaweeds’ metabolism: photosynthesis and respiration increase and decrease pH within the DBL (pHDBL), respectively. However, other metabolic processes, especially the uptake of inorganic nitrogen (Ni; NO3 and NH4+) may also affect the pHDBL. Using Macrocystis pyrifera, we hypothesized that (1) NO3 uptake will increase the pHDBL, whereas NH4+ uptake will decrease it, (2) if NO3 is cotransported with H+, increases in pHDBL would be greater under an OA treatment (pH = 7.65) than under an ambient treatment (pH = 8.00), and (3) decreases in pHDBL will be smaller at pH 7.65 than at pH 8.00, as higher external [H+] might affect the strength of the diffusion gradient. Overall, Ni source did not affect the pHDBL. However, increases in pHDBL were greater at pH 7.65 than at pH 8.00. CO2 uptake was higher at pH 7.65 than at pH 8.00, whereas HCO3 uptake was unaffected by pH. Photosynthesis and respiration control pHDBL rather than Ni uptake. We suggest that under future OA, Macrocystis pyrifera will metabolically modify its surface microenvironment such that the physiological processes of photosynthesis and Ni uptake will not be affected by a reduced pH.

Item Details

Item Type:Refereed Article
Keywords:Macrocystis, kelp, ocean acidification, nitrogen, climate change
Research Division:Biological Sciences
Research Group:Plant Biology
Research Field:Phycology (incl. Marine Grasses)
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Ecosystem Adaptation to Climate Change
Author:Fernandez, PA (Ms Pamela Fernandez Subiabre)
Author:Roleda, M (Dr Michael Roleda)
Author:Leal, PP (Mr Pablo Leal Sandoval)
Author:Hurd, CL (Associate Professor Catriona Hurd)
ID Code:112297
Year Published:2016
Deposited By:Centre for Ecology and Biodiversity
Deposited On:2016-11-03
Last Modified:2017-05-02
Downloads:0

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