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Influence of strong iron-binding ligands on cloud water oxidant capacity

Abstract

Iron (Fe) plays a dual role in atmospheric chemistry: it is involved in chemical and photochemical reactivity and serves as a micronutrient for microorganisms that have recently been shown to produce strong organic ligands. These ligands control the reactivity, mobility, solubility and speciation of Fe, which have a potential impact on Fe bioavailability and cloud water oxidant capacity.

In this work, the concentrations of Fe-binding ligands and the conditional stability constants were experimentally measured for the first time by Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-ACSV) technique in cloud water samples collected at puy de Dôme (France). The conditional stability constants, which indicate the strength of the Fe-ligand complexes, are higher than those considered until now in cloud chemistry (mainly Fe-oxalate). To understand the effect of Fe complexation on cloud water reactivity, we used the CLEPS cloud chemistry model. According to the model results, we found that Fe complexation impacts the hydroxyl radical formation rate: contrary to our expectations, Fe complexation by natural organic ligands led to an increase in hydroxyl radical production. These findings have important impacts on cloud chemistry and the global iron cycle.

Highlights

  • 95% of iron is complexed by strong organic ligands, likely produced by microorganisms.
  • Fe complexes stability constants are much higher than those used in cloud chemistry.
  • The presence of strong organic ligands induces an increase in hydroxyl radical production.
  • The analysis of sources and sinks of radical dotOH highlighted that complexed iron does not deplete HO2/O2−radical dot.


Reference

Aridane G. González, Angelica Bianco, Julia Boutorh, Marie Cheize, Gilles Mailhot, Anne-Marie Delort, Hélène Planquette, Nadine Chaumerliac, Laurent Deguillaume, Geraldine Sarthou. Influence of strong iron-binding ligands on cloud water oxidant capacity, Science of The Total Environment, Volume 829, 2022, 154642, ISSN 0048-9697, https://doi.org/10.1016/j.scitotenv.2022.154642.

Read the full article online

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Revisiting tolerance to ocean acidification: Insights from a new framework combining physiological and molecular tipping points of Pacific oyster

Abstract

Studies on the impact of ocean acidification on marine organisms involve exposing organisms to future acidification scenarios, which has limited relevance for coastal calcifiers living in a mosaic of habitats. Identification of tipping points beyond which detrimental effects are observed is a widely generalizable proxy of acidification susceptibility at the population level. This approach is limited to a handful of studies that focus on only a few macro-physiological traits, thus overlooking the whole organism response. Here we develop a framework to analyze the broad macro-physiological and molecular responses over a wide pH range in juvenile oyster. We identify low tipping points for physiological traits at pH 7.3–6.9 that coincide with a major reshuffling in membrane lipids and transcriptome. In contrast, a drop in pH affects shell parameters above tipping points, likely impacting animal fitness. These findings were made possible by the development of an innovative methodology to synthesize and identify the main patterns of variations in large -omic data sets, fitting them to pH and identifying molecular tipping points. We propose the broad application of our framework to the assessment of effects of global change on other organisms.

Graphical abstract

Tipping points of oyster transcriptome. (a–c) Frequency distribution of tipping point for piecewise linear relationships (left side). Linear and log-linear models (no tipping point) are under “Lin” name. Genes are grouped into three clusters of genes that co-vary together. The gray line indicates the distribution frequency of all genes irrespective of clusters. Groups of genes that exhibit neighboring tipping points with distribution frequencies >5% (shown as a dotted line), were grouped together. The segments above the bars indicate the groups of genes on which GO analyses were conducted. In each case, the gene that best represents the cluster according to module membership, gene significance for pH and R2 is presented as a function of pH as an example (right side). Tipping points and their 95% confidence intervals are shown in gray. The significance levels of the slopes are presented using stars (p < .001***, p < .01**, p < .05*). Gene names are as follows: LOC117690205: monocarboxylate transporter 12-like, LOC105317113: 60S ribosomal protein L10a, LOC105331560: protocadherin Fat 4

Reference

Lutier, M., Di Poi, C., Gazeau, F., Appolis, A., Le Luyer, J., & Pernet, F. (2022). Revisiting tolerance to ocean acidification: Insights from a new framework combining physiological and molecular tipping points of Pacific oyster. Global Change Biology, 00, 1– 16. https://doi.org/10.1111/gcb.16101
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Evidence that Pacific tuna mercury levels are driven by marine methylmercury production and anthropogenic inputs

Abstract

Pacific Ocean tuna is among the most-consumed seafood products but contains relatively high levels of the neurotoxin methylmercury. Limited observations suggest tuna mercury levels vary in space and time, yet the drivers are not well understood. Here, we map mercury concentrations in skipjack tuna across the Pacific Ocean and build generalized additive models to quantify the anthropogenic, ecological, and biogeochemical drivers. Skipjack mercury levels display a fivefold spatial gradient, with maximum concentrations in the northwest near Asia, intermediate values in the east, and the lowest levels in the west, southwest, and central Pacific. Large spatial differences can be explained by the depth of the seawater methylmercury peak near low-oxygen zones, leading to enhanced tuna mercury concentrations in regions where oxygen depletion is shallow. Despite this natural biogeochemical control, the mercury hotspot in tuna caught near Asia is explained by elevated atmospheric mercury concentrations and/or mercury river inputs to the coastal shelf. While we cannot ignore the legacy mercury contribution from other regions to the Pacific Ocean (e.g., North America and Europe), our results suggest that recent anthropogenic mercury release, which is currently largest in Asia, contributes directly to present-day human mercury exposure.

 

Graphical abstract


Spatial variability of skipjack mercury concentrations. Smoothed spatial contour maps of (A) observed and (B) standardized Hg concentrations (micrograms ⋅ grams−1, dw) in skipjack white muscle samples from the Pacific Ocean. The black dots represent the location of skipjack samples. Ocean areas correspond to the sample origin: NWPO, CNPO, NEPO, EPO, SWPO, and WCPO. The transparent dots represent the location of seawater samples with available and published MeHg data

 

Highlights

Humans are exposed to toxic methylmercury mainly by consuming marine fish. New environmental policies under the Minamata Convention rely on a yet-poorly-known understanding of how mercury emissions translate into fish methylmercury levels. Here, we provide the first detailed map of mercury concentrations from skipjack tuna across the Pacific. Our study shows that the natural functioning of the global ocean has an important influence on tuna mercury concentrations, specifically in relation to the depth at which methylmercury concentrations peak in the water column. However, mercury inputs originating from anthropogenic sources are also detectable, leading to enhanced tuna mercury levels in the northwestern Pacific Ocean that cannot be explained solely by oceanic processes.

 

Reference

Anaïs Médieu, David Point, Takaaki Itai, Hélène Angot, Pearse J. Buchanan, Valérie Allain, Leanne Fuller, Shane Griffiths, David P. Gillikin, Jeroen E. Sonke, Lars-Eric Heimbürger-Boavida, Marie-Maëlle Desgranges, Christophe E. Menkes, Daniel J. Madigan, Pablo Brosset, Olivier Gauthier, Alessandro Tagliabue, Laurent Bopp, Anouk Verheyden, Anne Lorrain. Evidence that Pacific tuna mercury levels are driven by marine methylmercury production and anthropogenic inputs. Proceedings of the National Academy of Sciences Jan 2022, 119 (2) e2113032119; DOI: 10.1073/pnas.2113032119

Read the article on PNAS website

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Recent advances in bivalve-microbiota interactions for disease prevention in aquaculture

Abstract
In bivalves, no clear-cut functional role of microbiota has yet been identified, although many publications suggest that they could be involved in nutrition or immunity of their host. In the context of climate change, integrative approaches at the crossroads of disciplines have been developed to explore the environment-host-pathogen-microbiota system. Here, we attempt to synthesize work on (1) the current methodologies to analyse bivalve microbiota, (2) the comparison of microbiota between species, between host compartments and their surrounding habitat, (3) how the bivalve microbiota are governed by environmental factors and host genetics and (4) how host-associated microorganisms act as a buffer against pathogens and/or promote recovery, and could thereby play a role in the prevention of disease or mortalities.

Graphical abstract

Figure 2. Host and environmental factors acting on bivalve microbiota.
Some of these factors, alone or in combination, have been shown to lead to dysbiosis, diseases and recovery.

Highlights :

  • High-throughput sequencing technologies enabled research on bivalve-microbiota interactions.
  • Bivalve-microbiota interactions depend on host factors nested within each other.
  • Microbiota interaction with surrounding environment is important for bivalve health.
  • Recent studies highlight the involvement of oyster microbiota in disease resistance.
  • Microbiome studies will provide new strategies to improve bivalve aquaculture.

Référence :

Christine Paillard, Yannick Gueguen, K Mathias Wegner, David Bass, Alberto Pallavicini, Luigi Vezzulli, Isabelle Arzul. Recent advances in bivalve-microbiota interactions for disease prevention in aquaculture. Current Opinion in Biotechnology, Volume 73, 2022, Pages 225-232. ISSN 0958-1669. https://doi.org/10.1016/j.copbio.2021.07.026.

 

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Post-mortem storage conditions and cooking methods affect long-chain omega-3 fatty acid content in Atlantic mackerel (Scomber scombrus)

Omega-3 fatty acids are essential for human health and are found especially in marine fish. They degrade easily over time and at high temperatures, but to what extent? This is what we tested on mackerel. The loss of omega-3 was not particularly high in the first few hours after the fishes were caught, but it was still best to store them as cold as possible. For cooking, it is better to grill the mackerel fillet with its skin than to steam it. Bon appétit !

 

Abstract

Long-chain omega-3 fatty acids such as eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) are health beneficial lipids found in high concentration in pelagic fishes, including Atlantic mackerel. While EPA and DHA are sensitive to oxidation during fish storage and processing, post-mortem degradation in the first hours following fish death is poorly documented. Here, we stored fish at two temperatures (2–4 °C and 18–20 °C) and monitored EPA + DHA content in dorsal fillet 6, 12 and 24 h after fish death and after cooking (grill or steam). Storage duration was the only influencing factor, and EPA + DHA loss was faster at 18–20 °C. Six hours after fish death, EPA + DHA content decreased by 1.3 ± 1.3 mg.g−1 dw (9.6 ± 9.5% of the initial content) but it was highly variable among individuals. Handling between fishing and storage should be as short and as cool as possible to preserve EPA + DHA and food safety. Regarding cooking, EPA + DHA and mono-unsaturated fatty acids increased in grilled fillets.

 

Graphical abstract

Fig.1: Outline of the sampling design testing for the influence of storage temperature (2–4 ◦C and 18–20 ◦C), storage duration (from T6 to T24 hours), and cooking method (grill and steam) on the fatty acid content of the Atlantic mackerel Scomber scombrus. Dark squares indicate the muscle sampling position at each step, and the grey ones the previously sampled positions. For cooking, we sampled the left side of the fish.

 

Highlights

  • Storage duration (< 24h) had a higher impact than storage temperature on EPA + DHA content in mackerel dorsal fillet.
  • EPA + DHA and mono-unsaturated fatty acids content increased in grilled fillets.
  • EPA + DHA losses in mackerel dorsal fillet were highly variable among individuals.

 

Reference

Fany Sardenne, Eleonora Puccinelli, Marie Vagner, Laure Pecquerie, Antoine Bideau, et al.. Post-mortem storage conditions and cooking methods affect long-chain omega-3 fatty acid content in Atlantic mackerel (Scomber scombrus). Food Chemistry, Elsevier, 2021, 359, pp.129828. ⟨10.1016/j.foodchem.2021.129828⟩.

The article is also available in open access on HAL : https://hal.archives-ouvertes.fr/hal-03215360

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Copyright : Laboratoire LEMAR- 2018

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