Comment on “The complex effects of ocean acidification on the prominent N2-fixing cyanobacterium Trichodesmium”

Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Science 357 (2017): eaao0067, doi:10.1126/science.aao0067.Hong et al. (Reports, 5 May 2017, p. 527) suggested that previous studies of the biogeochemically significant marine cyanobacterium Trichodesmium showing increased growth and nitrogen fixation at projected future high CO2 levels suffered from ammonia or copper toxicity. They reported that these rates instead decrease at high CO2 when contamination is alleviated. We present and discuss results of multiple published studies refuting this toxicity hypothesis

Nutrient Cycles and Marine Microbes in a CO2-Enriched Ocean

The ocean carbon cycle is tightly linked with the cycles of the major nutrient elements nitrogen, phosphorus, and silicon. It is therefore likely that enrichment of the ocean with anthropogenic CO2 and attendant acidification will have large consequences for marine nutrient biogeochemistry, and for the microbes that mediate many key nutrient transformations. The best available evidence suggests that the nitrogen cycle may respond strongly to higher CO2 through increases in global N2 fixation and possibly denitrification, as well as potential decreases in nitrification. These trends could cause nitrification to become a nitrogen cycle bottleneck, by increasing the flux of N2 fixed into ammonium while decreasing the fraction being oxidized to nitrate and nitrate. The consequences could include reduced supplies of oxidized nitrogen substrates to denitrifiers, lower levels of nitrate-supported new primary production, and expansion of the regenerated production system accompanied by shifts in current phytoplankton communities. The phosphorus and silicon cycles seem less likely to be directly affected by enhanced CO2 conditions, but will undoubtedly respond indirectly to changing carbon and nitrogen biogeochemistry. A review of culture experiments that examined the effects of increased CO2 on elemental ratios of phytoplankton suggests that for most cyanobacteria and eukaryotes, C:N and N:P ratios will either remain at Redfield values or increase substantially. Natural plankton community CO2 manipulation experiments show much more mixed outcomes, with both increases and decreases in C:N and N:P ratios reported at future CO2 levels. We conclude our review with projections of overall trends in the cycles of nitrogen, phosphorus, and silicon over the next century as they respond to the steady accumulation of fossil-fuel derived CO2 in a rapidly changing ocean

Combined effects of CO 2 level, light intensity, and nutrient availability on the coccolithophore Emiliania huxleyi

Abstract(#br)Continuous accumulation of fossil CO 2 in the atmosphere and increasingly dissolved CO 2 in seawater leads to ocean acidification (OA), which is known to affect phytoplankton physiology directly and/or indirectly. Since increasing attention has been paid to the effects of OA under the influences of multiple drivers, in this study, we investigated effects of elevated CO 2 concentration under different levels of light and nutrients on growth rate, particulate organic (POC) and inorganic (PIC) carbon quotas of the coccolithophorid Emiliania huxleyi . We found that OA treatment (pH 7.84, CO 2 = 920 μatm) reduced the maximum growth rate at all levels of the nutrients tested, and exacerbated photo-inhibition of growth rate under reduced availability of phosphate (from 10.5 to 0.4..

A comparative study of iron and temperature interactive effects on diatoms and Phaeocystis antarctica from the Ross Sea, Antarctica

In the future, temperature and iron availability are predicted to change in the coastal polynyas of Antarctica, which are the most biologically productive regions of the Southern Ocean. We examined the individual and combined effects of iron addition (+500 nM) and temperature increase (4°C) on Phaeocystis antarctica and several dominant diatom species isolated from the McMurdo Sound sector of the Ross Sea. Iron addition increased growth, carbon fixation, iron uptake rates, cellular carbon quota, and cell size of almost all tested species, while temperature increase only affected certain species. Concurrent increases in temperature and iron synergistically stimulated the growth rates of some species, particularly Pseudo-nitzschia subcurvata. The diversified responses of these phytoplankton to iron and temperature may help explain the current spatial and temporal distributions of diatoms and prymnesiophytes in the Ross Sea. In the future, potential temperature and iron increases may promote the growth of the diatoms Chaetoceros sp., Fragilariopsis cylindrus, and especially P. subcurvata. In contrast, growth rates of P. antarctica did not increase at higher temperatures, suggesting that a shift in community composition toward diatoms may occur under warmer conditions in this biologically and biogeochemically important Southern Ocean polynya region

A bibliometric analysis of optic atrophy from 2003 to 2023: research trends and hot spots

BackgroundOptic atrophy (OA) is primarily caused by damage to the retinal pathway system, including widespread degeneration of retinal ganglion cells and axons, leading to visual impairment and blindness. Despite its clinical significance and diverse etiological factors, there is currently a lack of comprehensive bibliometric analyses exploring research trends and hotspots within this field.MethodThis study retrieved relevant literature on OA published between 2003 and 2023 from the Web of Science Core Collection database. We conducted a bibliometric analysis using tools such as CiteSpace, VOSviewer, and SCImago Graphica to examine annual publication trends, co-occurrence patterns, collaborative networks among countries and institutions, and the evolution of research hotspots of OA.ResultsA total of 5,274 publications were included in the bibliometric analysis, comprising 4,561 research articles and 713 review articles. The United States emerged as the leading country in OA research, followed by Germany and China. Over the past two decades, the primary research hotspots focused on “mitochondrial dysfunction,” “hereditary optic neuropathy,” “ocular hypertension” and “diagnostic techniques.” Future research trends are likely to revolve around “molecular mechanisms” and “therapeutic targets.”ConclusionThis bibliometric analysis provides an overview of research developments in OA over the past 20 years, highlighting the emphasis on the pathological basis of OA and advancements in diagnostic and therapeutic approaches. Future studies should continue to explore the molecular basis of mitochondrial dysfunction to identify potential gene therapy targets for treating OA

Cysteine-free Intramolecular Ligation of N-Sulfanylethylanilide Peptide Using 4-Mercaptobenzylphosphonic Acid : Synthesis of Cyclic Peptide, Trichamide

An N-sulfanylethylanilide (SEAlide)-based ligation was developed for the preparation of trichamide, a thiazole-containing cyclic peptide isolated from bloom-forming cyanobacterium Trichodesmium erythraeum. In this cysteine-free ligation, 4-mercaptobenzylphosphonic acid (MBPA) functions as a dual promoter both for the N–S acyl-transfer-mediated activation of the SEAlide unit and for subsequent ligation. Furthermore, we established a high-yielding route to enantiomerically pure thiazole amino acids using a one-pot Hantzsch process

Iron Deficiency Increases Growth and Nitrogen-Fixation Rates of Phosphorus-Deficient Marine Cyanobacteria

Marine dinitrogen (N2)-fixing cyanobacteria have large impacts on global biogeochemistry as they fix carbon dioxide (CO2) and fertilize oligotrophic ocean waters with new nitrogen. Iron (Fe) and phosphorus (P) are the two most important limiting nutrients for marine biological N2 fixation, and their availabilities vary between major ocean basins and regions. A long-standing question concerns the ability of two globally dominant N2-fixing cyanobacteria, unicellular Crocosphaera and filamentous Trichodesmium, to maintain relatively high N2-fixation rates in these regimes where both Fe and P are typically scarce. We show that under P-deficient conditions, cultures of these two cyanobacteria are able to grow and fix N2 faster when Fe deficient than when Fe replete. In addition, growth affinities relative to P increase while minimum concentrations of P that support growth decrease at low Fe concentrations. In Crocosphaera, this effect is accompanied by a reduction in cell sizes and elemental quotas. Relatively high growth rates of these two biogeochemically critical cyanobacteria in low-P, low-Fe environments such as those that characterize much of the oligotrophic ocean challenge the common assumption that low Fe levels can have only negative effects on marine primary producers. The closely interdependent influence of Fe and P on N2-fixing cyanobacteria suggests that even subtle shifts in their supply ratio in the past, present and future oceans could have large consequences for global carbon and nitrogen cycles

Continuous and comprehensive atmospheric observations in Beijing : a station to understand the complex urban atmospheric environment

Peer reviewe