Preprints
https://doi.org/10.5194/bg-2021-18
https://doi.org/10.5194/bg-2021-18

  22 Feb 2021

22 Feb 2021

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

Response of tropical marine benthic diatoms exposed to elevated irradiance and temperature

Sazlina Salleh1,2 and Andrew McMinn3,4 Sazlina Salleh and Andrew McMinn
  • 1Centre for Policy Research and International Studies (CenPRIS), Universiti Sains Malaysia, 11800, Minden, Pulau Pinang, Malaysia
  • 2Centre for Marine and Coastal Studies (CEMACS), Universiti Sains Malaysia, 11800, Minden, Pulau Pinang, Malaysia
  • 3Institute of Marine and Antarctic Studies (IMAS), University of Tasmania, Box 252-77, Hobart 7001, Tasmania, Australia
  • 4College of Marine Life Science, Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China

Abstract. Shallow tropical marine environments are likely to experience future water temperatures that will challenge the ability of life to survive. Changes in temperature and irradiance during tidal cycles in the Tanjung Rhu estuary, Langkawi, Malaysia in 2007 did not significantly affect the benthic diatom communities, although, higher photosynthetic parameters, such as maximum relative electron transport rate (rETRmax), photosynthetic efficiency (α), maximum quantum yield (Fv/Fm) and effective quantum yield (∆F/Fm'), were recorded at high tide when the temperatures were lower. However, when benthic diatoms were experimentally exposed to irradiances of 1800 µmol photons m−2 s−1, they were only able to photosynthesize at temperatures < 50 °C. Above this temperature, no photosynthetic activity was observed. Not only did high temperatures at high irradiance affect the algal communities, but limited photosynthetic activity was also observed in samples when exposed to limited irradiance. Recovery rates were highest at the lowest temperatures and decreased as the temperature increased. The recovery rates for samples exposed to temperatures of 40 °C were 4.01E-03 ± 0.002 and decreased to 1.01E-05 ± 0.001 at 60 °C, indicating irreversible damage to Photosystem II (PSII). These characteristics suggest that the benthic diatom communities in this estuary are already suffering from thermal damage and that enhanced photoinhibition would result if exposed to elevated temperatures, especially during low tide. 50 °C is apparently a temperature threshold for tropical estuarine benthic microalgal communities. Future warming is likely to cause this temperature to occur more frequently, which will cause a reduction in benthic primary production.

Sazlina Salleh and Andrew McMinn

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-18', Anonymous Referee #1, 10 Mar 2021
  • RC2: 'Comment on bg-2021-18', Siqueiros-Beltrones, David A, 09 Apr 2021

Sazlina Salleh and Andrew McMinn

Sazlina Salleh and Andrew McMinn

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Short summary
The benthic diatom communities in Tanjung Rhu, Malaysia, were regularly exposed to high light and temperature variability during the tidal cycle resulting in low photosynthetic efficiency. We examined the impact of high temperatures on diatoms' photosynthetic capacities, and temperatures beyond 50 °C have caused severe photoinhibition. At the same time, those exposed to temperatures of 40 °C did not show any sign of photoinhibition.
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