Future Responses of Marine Primary Producers to Environmental Changes

Gao, Kunshan; Zhao, Wenyan; Beardall, John

doi:10.1002/9781119986782.ch9

Cited by 2 publications

(2 citation statements)

References 165 publications

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“…The reduced O 2 availability aided in such adjustment. On the other hand, elevated pCO 2 associated with the acidic stress is known to enhance respiration rate of diatoms to accommodate the increased energy demands involved in maintaining intracellular pH homeostasis (Wu et al, 2010;Goldman et al, 2017;Qu et al, 2021;Gao et al, 2022). However, a recent study suggests that the increased respiration may not be sufficient to counteract the negative effects induced by acidic stress in darkness, as the cell growth rate of the diatom P. tricornutum decreased in a 48-hour period of complete darkness (Qu et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness

Sun,

Zhang,

et al. 2024

Front. Mar. Sci.

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Respiratory activity in the oceans is declining due to the expansion of hypoxic zones and progressive deoxygenation, posing threats to marine organisms along with impacts of concurrent ocean acidification. Therefore, understanding the combined impacts of reduced pO2 and elevated pCO2 on marine primary producers is of considerable significance. Here, to simulate diatoms’ sinking into the aphotic zone of turbid coastal water, we exposed the diatoms Thalassiosira pseudonana and Thalassiosira weissflogii in darkness at 20°C to different levels of pO2 and pCO2 conditions for ~3 weeks, and monitored their biomass density, photosynthetic activity and dark respiration, and examined their recovery upon subsequent exposure to light at 20°C, simulating surface water conditions. Along with decreased cell abundance and size, measured photosynthetic capacity and dark respiration rates in these two diatoms both gradually decreased during the prolonged darkness. Reduced pO2 alone did not negatively affect the photosynthetic machinery in both the dark-survived diatom, and enhanced their subsequent recovery upon light exposure. Nevertheless, the combination of the elevated pCO2 and reduced pO2 (equivalent to hypoxia) led to the biomass loss by about 90% in T. pseudonana, and delayed the recovery of both species upon subsequent exposure to light, though it did not reduce the cell concentration of T. weissflogii during the elongated darkness. Our results suggest that reduced O2 availability diminishes the abilities of the diatoms to cope with the acidic stress associated with ocean acidification, and the expansion of hypoxic waters could delay the photosynthetic recovery of coastal diatoms when they are transported upwards through mixing from dark layers to sunlit waters.

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Section: Discussionmentioning

confidence: 99%

Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness

Sun,

Zhang,

et al. 2024

Front. Mar. Sci.

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“…To drive photosynthesis, photoautotrophs mainly utilize photosynthetically active radiation (400–700 nm, PAR), but they are often inevitably exposed to harmful UVR. Although UV‐B radiation (280–315 nm) accounts for less than 1% of incident solar radiation in most regions of the world, it is usually more harmful for photosynthetic organisms than UV‐A (315–400 nm) in terms of biologically weighted impacts, as UV‐B photons are more photobiologically active than UV‐A which is about 6–8% of the total solar energy in tropical and subtropical regions (Gao et al 2022). It has been documented that solar UVR can penetrate to 80 m deep in the pelagic region of oceans (Piazena et al 2002; Tedetti et al 2007).…”

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confidence: 99%

Impact of ultraviolet radiation nearly overrides the effects of elevated pCO₂ on a prominent nitrogen‐fixing cyanobacterium

Gao

2023

Limnology & Oceanography

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Although the marine N 2 -fixers Trichodesmium spp. are affected by increasing pCO 2 and by ultraviolet radiation (UVR) in their habitats, little is known on their potential responses to future ocean acidification in the presence of UVR. We grew Trichodesmium at two pCO 2 levels (410 and 1000 μatm) under natural sunlight, documented the filament length, growth, and chlorophyll content after its acclimation to the pCO 2 treatments, and measured its carbon and N 2 fixation rates under different solar radiation treatments with or without UVR. We showed that the elevated pCO 2 did not significantly alter the diazotroph's growth, filament length, or pigment content, and its photosynthetic rate was only affected by solar radiation treatments rather than the pCO 2 levels. The presence of UV-A and UV-B inhibited photosynthesis by 10-22% and 17-21%, respectively. Inhibition of N 2 fixation by UV-B was proportional to its intensity, whereas UV-A stimulated N 2 fixation at low, but inhibited it at high, intensities. Elevated pCO 2 only stimulated N 2 fixation under moderate levels of solar radiation. The simulated depth profile of N 2 fixation in the water column showed that UV-induced inhibition dominated the combined effects of elevated pCO 2 and UVR at 0-30 m depth and the combination of these factors enhanced N 2 fixation at 30-60 m depth, but this effect diminished in deeper water. Our results suggest that Trichodesmium could be influenced more by UVR than by pCO 2 and their combined action result in negative effects on N 2 fixation under high solar radiation, but positive effects under low to moderate solar radiation.

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Future Responses of Marine Primary Producers to Environmental Changes

Cited by 2 publications

References 165 publications

Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness

Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness

Impact of ultraviolet radiation nearly overrides the effects of elevated pCO₂ on a prominent nitrogen‐fixing cyanobacterium

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Future Responses of Marine Primary Producers to Environmental Changes

Cited by 2 publications

References 165 publications

Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness

Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness

Impact of ultraviolet radiation nearly overrides the effects of elevated pCO2 on a prominent nitrogen‐fixing cyanobacterium

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Impact of ultraviolet radiation nearly overrides the effects of elevated pCO₂ on a prominent nitrogen‐fixing cyanobacterium