Phytoplankton responses to aluminum enrichment in the South China Sea

Limnology & Oceanography

et al. 2021

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Recent studies indicate that aluminum (Al) could play an important role in the ocean carbon cycle by increasing phytoplankton carbon fixation and reducing organic carbon decomposition. However, how Al may influence the decomposition of organic carbon has not yet been explicitly examined. Here we report the effects of Al on carbon fixation by marine diatoms and their subsequent decomposition. By using radiocarbon as a tracer, the carbon fixation and decomposition of three model marine diatoms were examined in Aquil* media at different concentrations (0, 40, 200, and 2000 nM) of dissolved Al. Addition of Al enhanced net carbon fixation by the diatoms in the declining growth phase (by 9%-29% for Thalassiosira pseudonana, 15%-20% for T. oceanica, 15%-23% for T. weissflogii). Under axenic conditions the decomposition rates (d À1 ) of the diatomproduced particulate organic carbon (POC) significantly decreased (by 21%-57% for T. pseudonana, 0%-41% for T. oceanica, 29%-58% for T. weissflogii) in the Al-enriched treatments. In the presence of bacteria, the decomposition rates of T. weissflogii-produced POC were still 37%-38% lower in Al-enriched treatments compared to the control. Significant increases in cell size, cellular carbon content (pmol C/cell) and cellular carbon density (pmol C/μm 3 ) of T. weissflogii were also observed in the Al-enriched treatments compared to the control. The Al-related increase in net carbon fixation and cell size, and the decrease in POC decomposition rate may facilitate carbon export to ocean depths. The study provides new evidence for the iron-aluminum hypothesis, which suggests that Al could increase phytoplankton uptake of atmospheric CO 2 and influence climate change.

Section: Beneficial Effects Of Al On the Growth And Carbon Fixation Of Marine Phytoplanktonsupporting

confidence: 91%

Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

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Aluminum increases net carbon fixation by marine diatoms and decreases their decomposition: Evidence for the iron–aluminum hypothesis

Zhou

Limnology & Oceanography

et al. 2021

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“…A recent study shows that enhanced nitrogen fixation and increased growth of nitrogen-fixers occurs in the presence of Al. By adding Al to natural seawater collected from the South China Sea, a large subtropical and tropical marginal sea, we observed enhanced growth of Trichodesmium, and increased nitrogen fixation by the whole plankton community (Zhou et al 2017). Another study indicated that addition of a low level of Al (200 nM) to natural seawater in the South China Sea could not only stimulate nitrogen fixation by the whole plankton community, but could also increase the growth and the nifH gene expression of two nitrogen-fixers (Trichodesmium spp.…”

Section: Enhanced Nitrogen Fixation In the Presence Of Almentioning

confidence: 90%

Aluminum effects on marine phytoplankton: implications for a revised Iron Hypothesis (Iron–Aluminum Hypothesis)

et al. 2018

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In contrast to substantial studies and established knowledge of aluminum (Al) effects 2 (mainly toxicity) on freshwater organisms and terrestrial plants, and even on human 3 health, only a few studies of Al effects on marine organisms have been reported, and our 4 understanding of the role of Al in marine biogeochemistry is limited. In this paper, we 5 the role of Al in the stimulation of phytoplankton growth and carbon sequestration in the 1 ocean depths. 2

“…There has been an upsurge of interest in the effects of Al on marine organisms in recent years. With reference to marine phytoplankton, recent studies have reported both the toxicity (Gillmore et al, 2016;Golding et al, 2015) and the beneficial effects of Al on marine phytoplankton growth (Liu et al, 2018;Zhou et al, 2018aZhou et al, , 2018bZhou et al, , 2016. However, little is known about the uptake kinetics and the intracellular fate of Al in marine phytoplankton, which are important if we are to understand the mechanisms responsible for the biological effects of Al.…”

Section: Introductionmentioning

confidence: 99%

Uptake and subcellular distribution of aluminum in a marine diatom

Zhou

Ecotoxicology and Environmental Safety

et al. 2019

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Aluminum (Al) is widespread in the environment including the ocean. The effects of Al on marine organisms have attracted more and more attention in recent years. However, the mechanisms of uptake of Al by marine organisms and the subcellular distribution of Al once assimilated are unknown. Here we report the uptake and subcellular distribution of Al in a marine diatom Thalassiosira weissflogii. Short-term (< 120 min) uptake experiments showed that the Al uptake rate by the diatom was 0.033 ± 0.013 fmol/cell/min (internalization flux normalized to the exposure Al concentration of 2 µM = 0.034 ± 0.013 nmol•m-2 •min-1 •nM-1). Subcellular fractionation experiments showed that the internalized Al was partitioned to subcellular components in the following order: granules (69 ± 5%) > debris (17 ± 4%) > organelles (12 ± 2%) > heat-stable peptides (HSP) (~2%) > heat-denaturable proteins (HDP) (< 1%), indicating that the majority of intracellular Al was detoxified and stored in inorganic forms. The subcellular distribution of Al in the diatom is different from that of Al in freshwater green algae, in which most of the internalized Al is partitioned to organelles. We also evaluated an artificial seawater-based EDTA rinse solution to remove Al adsorbed on the diatom cell surface. Overall, our study provides new information to understand the mechanisms of uptake of Al by marine diatoms, and the mechanisms responsible for the biological effects (both toxic and beneficial) of Al on the growth of marine phytoplankton, especially diatoms.