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Botanica Marina

Editor-in-Chief: Dring, Matthew J.

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1437-4323
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Daily timing of emersion and elevated atmospheric CO2 concentration affect photosynthetic performance of the intertidal macroalga Ulva lactuca (Chlorophyta) in sunlight

Dinghui Zou
  • 1Marine Biology Institute, Science Center, Shantou University, Shantou, Guangdong 515063, China
/ Kunshan Gao
  • 2Marine Biology Institute, Science Center, Shantou University, Shantou, Guangdong 515063, China and State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan, Hubei 430072, China
/ Zuoxi Ruan
  • 3Marine Biology Institute, Science Center, Shantou University, Shantou, Guangdong 515063, China
Published Online: 2007-12-12 | DOI: https://doi.org/10.1515/BOT.2007.031

Abstract

The lunar day differs in length from the solar day so that times of low tide vary from day to day. Thus, aerial exposure of intertidal seaweeds may be during the day or during the night. We measured photosynthetic CO2 assimilation rates of the intertidal green macroalga Ulva lactuca during exposures of varied daily timings during sunny days of summer to establish how photosynthetic performance responds to emersion timing under varied CO2 levels [at ambient (360 ppmv) and 2× ambient (720 ppmv) atmospheric CO2 concentrations]. There was an increase in net photosynthetic rates following some duration of exposure when the initial timing of exposure occurred during early morning (06.30 h) and late afternoon (17.15 h). In contrast, net rates exhibited a sharp decline with exposure duration when the initial timing of exposure occurred at 09.30 h, 15.30 h and especially at noon (12.30 h), implying the occurrence of a severe photoinhibition resulting from mid-day insolation. Doubled atmospheric CO2 concentration significantly enhanced the emersed photosynthetic rates, indicating that the emersed photosynthesis is CO2-limited at ambient CO2 levels. However, increasing CO2 barely stimulates the emersed photosynthetic rates during mid-day insolation.

Keywords: CO2; emersion; photosynthesis; tidal rhythm; Ulva lactuca

About the article

Corresponding author


Received: 2006-12-22

Accepted: 2007-08-02

Published Online: 2007-12-12

Published in Print: 2007-12-01


Citation Information: Botanica Marina, ISSN (Online) 14374323, ISSN (Print) 00068055, DOI: https://doi.org/10.1515/BOT.2007.031.

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