Calcification in Three Common Calcified Algae from Phuket, Thailand: Potential Relevance on Seawater Carbonate Chemistry and Link to Photosynthetic Process

Buapet, Pimchanok; Sinutok, Sutinee

doi:10.3390/plants10112537

Cited by 4 publications

(5 citation statements)

References 79 publications

(137 reference statements)

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“…A greater role of photosynthesis by LCI ochrophytes than chlorophytes in calci cation is supported by DIC changes primarily attributed to photosynthesis in Padina sp., while to a lesser extent in Halimeda sp. where DIC changes were primarily associated with calci cation (Buapet & Sinutok, 2021).…”

Section: Discussionmentioning

confidence: 99%

Stable Carbon and Oxygen Isotopes Indicate Photophysiology and Calcification Mechanisms of Macroalgae on Little Cayman Reefs

Koch

McNicholl

Manfrino³

et al. 2023

Preprint

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Tropical macroalgae serve importance ecological roles on coral reefs but can supplant corals in phase shifts as shown worldwide. Thus, it is important to understand their fundamental photophysiology and calcification mechanisms. We examined organic d13C, organic+inorganic d15N, inorganic CaCO3 d13C and d18O, and organic %C, %N, C:N of abundant macroalgae on Little Cayman Island (LCI) reefs across irradiance gradients (5-2,000 mmol m-2 s-1). We hypothesized macroalgae utilize greater CO2 in low light as carbon concentration mechanisms (CCMs) for HCO3- uptake have higher energetic costs. We proposed that calcification mechanisms are influenced by light and Ci-use strategy in addition to taxonomy. LCI macroalgae had organic d13C values (-12‰ to -25‰) indicative of CCMs and exhibited only 1-3‰ 13C depletion in irradiances <5 mmol photons m-2 s-1. Ochrophyte d13C values were enriched in 13C at low nitrogen indicative of efficient CCMs. Macroalgae exhibited four clusters of thalli CaCO3 d13C that were distinctly taxon-specific. Rhodophytes exhibited the most negative inorganic d13C and d18O values (-4.1‰ ± 0.7‰; -3.7‰ ± 0.4‰) an indication of high calcifying space pH and rapid calcification, potentially reliant on active ion transport. Relatively higher organic C fractionation when utilizing greater CO2 for photosynthesis was reflected in depleted thalli carbonates in species/genus with positive d13C values. Increasing ocean CO2 is not likely to enhance dominant LCI macroalgal photosynthesis as these reef macroalgae utilize CCMs across a broad range of irradiances; however, effects on calcification may be taxon specific based on the degree of biotic control elucidated in thalli carbonate isotopes.

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Section: Discussionmentioning

confidence: 99%

Stable Carbon and Oxygen Isotopes Indicate Photophysiology and Calcification Mechanisms of Macroalgae on Little Cayman Reefs

Koch

McNicholl

Manfrino³

et al. 2023

Preprint

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“…Finally, the chemical composition of DOC itself also affects its lability, and this composition is not well understood for most macroalgae. Macroalgae DOC contains high quantities of phenolic and humic-like compounds, which are typically more recalcitrant than other molecules (Wada et al, 2008;Buck-Wiese et al, 2022;Feng et al, 2022).…”

Section: Main Macroalgal Carbon Sequestration Pathwaysmentioning

confidence: 99%

“…Advances in numerous fingerprinting techniques offer promising prospects in that regard. For example, eDNA analysis can be used to verify the presence of macroalgae carbon in sediments or deep-water samples (Ortega et al, 2019;Frigstad et al, 2021;Ørberg et al, 2022), while the increasingly widespread use of Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) or antibody-based techniques can enable the detection of specific recalcitrant molecular species derived from macroalgae (Buck-Wiese et al, 2022;Feng et al, 2022;Li et al, 2022). Ultimately, verifying sequestration of macroalgae carbon will require dating of sediments or water masses, whose sampling and analysis is often costly.…”

Section: Mapping Macroalgal Carbon Sequestration Potential and Direct...mentioning

confidence: 99%

“…For instance, alkalinity produced via carbonate dissolution, denitrification, or sulfate reduction can enhance the carbon sink capacity of blue carbon sediments, as long as those metabolic products are permanently prevented from being re‐oxidized (Reithmaier et al ., 2021). By contrast, the consumption of alkalinity can offset the carbon sequestration capacity of blue carbon ecosystems (Bach et al ., 2021; Buapet & Sinutok, 2021; van Dam et al ., 2021).…”

Section: Mapping Macroalgal Carbon Sequestration Potential and Direct...mentioning

confidence: 99%

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Carbon sequestration and climate change mitigation using macroalgae: a state of knowledge review

et al. 2023

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The conservation, restoration, and improved management of terrestrial forests significantly contributes to mitigate climate change and its impacts, as well as providing numerous co‐benefits. The pressing need to reduce emissions and increase carbon removal from the atmosphere is now also leading to the development of natural climate solutions in the ocean. Interest in the carbon sequestration potential of underwater macroalgal forests is growing rapidly among policy, conservation, and corporate sectors. Yet, our understanding of whether carbon sequestration from macroalgal forests can lead to tangible climate change mitigation remains severely limited, hampering their inclusion in international policy or carbon finance frameworks. Here, we examine the results of over 180 publications to synthesise evidence regarding macroalgal forest carbon sequestration potential. We show that research efforts on macroalgae carbon sequestration are heavily skewed towards particulate organic carbon (POC) pathways (77% of data publications), and that carbon fixation is the most studied flux (55%). Fluxes leading directly to carbon sequestration (e.g. carbon export or burial in marine sediments) remain poorly resolved, likely hindering regional or country‐level assessments of carbon sequestration potential, which are only available from 17 of the 150 countries where macroalgal forests occur. To solve this issue, we present a framework to categorize coastlines according to their carbon sequestration potential. Finally, we review the multiple avenues through which this sequestration can translate into climate change mitigation capacity, which largely depends on whether management interventions can increase carbon removal above a natural baseline or avoid further carbon emissions. We find that conservation, restoration and afforestation interventions on macroalgal forests can potentially lead to carbon removal in the order of 10's of Tg C globally. Although this is lower than current estimates of natural sequestration value of all macroalgal habitats (61–268 Tg C year−1), it suggests that macroalgal forests could add to the total mitigation potential of coastal blue carbon ecosystems, and offer valuable mitigation opportunities in polar and temperate areas where blue carbon mitigation is currently low. Operationalizing that potential will necessitate the development of models that reliably estimate the proportion of production sequestered, improvements in macroalgae carbon fingerprinting techniques, and a rethinking of carbon accounting methodologies. The ocean provides major opportunities to mitigate and adapt to climate change, and the largest coastal vegetated habitat on Earth should not be ignored simply because it does not fit into existing frameworks.

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“…and Padina sp. (Buapet and Sinutok, 2021). Dark calcification rate and subsequent light calcification rate need to be measured in future studies.…”

Section: Conclusion and Future Considerationsmentioning

confidence: 99%

Impacts of nighttime hypoxia on the physiological performance of Red Sea macroalgae under peak summer temperature

et al. 2022

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Eutrophication-induced hypoxic sites are increasingly reported in coastal regions. At the same time, ocean warming, water column stratification, and changing circulation lead to open-ocean deoxygenation. In coastal areas and reefs with dense vegetation, aquatic organisms can be exposed to oxygen limitation stress where oxygen concentration reaches extremely low levels, particularly during nighttime once photosynthetic O2 production has ceased. Despite scientists being aware of this for decades, little is known about the impact of deoxygenation on the physiology of marine primary producers, such as macroalgae. In the Red Sea, in particular, the physiological adaptations of macroalgae under future climate scenarios are nonexistent. Here, we investigate the impact of different oxygen levels (6.5, 2.5, and 1.3 mg O2 L-1) at night for three conspicuous Red Sea macroalgae species Halimeda opuntia and Padina boryana (calcareous) and the brown algae Sargassum latifolium (noncalcifying). We monitored algal physiological responses during a 12-hour nighttime (dark) period at 32°C by measuring photochemical efficiency (Fv/Fm), respiration rates, and cellular viability. No lethal thresholds were detected. However, both deoxygenation treatments decreased respiration rates and induced changes in cellular activity, and only under severe hypoxia was a decrease in photochemical efficiency observed in all species. We calculated sublethal O2 thresholds SLC(50) of 1.2 ± 0.1, 1.5 ± 0.1, and 1.7 ± 0.1 mg O2 L-1 for H. opuntia, P. boryana, and S. latifolium, respectively. Therefore, the effects of nighttime hypoxia are evident over short timescales and may impact ecosystems via reduced primary production. Future consequences of persistent hypoxia and subsequent performance in multifaceted stressor exposures will provide a fundamental understanding of hypoxia’s threat to biodiversity and ecosystems.

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Calcification in Three Common Calcified Algae from Phuket, Thailand: Potential Relevance on Seawater Carbonate Chemistry and Link to Photosynthetic Process

Cited by 4 publications

References 79 publications

Stable Carbon and Oxygen Isotopes Indicate Photophysiology and Calcification Mechanisms of Macroalgae on Little Cayman Reefs

Stable Carbon and Oxygen Isotopes Indicate Photophysiology and Calcification Mechanisms of Macroalgae on Little Cayman Reefs

Carbon sequestration and climate change mitigation using macroalgae: a state of knowledge review

Impacts of nighttime hypoxia on the physiological performance of Red Sea macroalgae under peak summer temperature

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