Contrasting effects of acidification and warming on dimethylsulfide 2 concentrations during a temperate estuarine fall bloom mesocosm 3 experiment

The effects of ocean acidification and warming on the concentrations of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) were investigated during a mesocosm experiment in the Lower St. Lawrence Estuary (LSLE) in the fall of 2014. Twelve mesocosms covering a range of pHT (pH on the total hydrogen ion concentration scale) from 8.0 to 7.2, corresponding to a range of CO2 partial pressures (pCO2) from 440 to 2900 μatm, at two temperatures (in situ and C5 °C; 10 and 15 °C) were monitored during 13 days. All mesocosms were characterized by the rapid development of a diatom bloom dominated by Skeletonema costatum, followed by its decline upon the exhaustion of nitrate and silicic acid. Neither the acidification nor the warming resulted in a significant impact on the abundance of bacteria over the experiment. However, warming the water by 5 °C resulted in a significant increase in the average bacterial production (BP) in all 15 °C mesocosms as compared to 10 °C, with no detectable effect of pCO2 on BP. Variations in total DMSP (DMSPt DparticulateCdissolved DMSP) concentrations tracked the development of the bloom, although the rise in DMSPt persisted for a few days after the peaks in chlorophyll a. Average concentrations of DMSPt were not affected by acidification or warming. Initially low concentrations of DMS (< 1 nmol L-1) increased to reach peak values ranging from 30 to 130 nmol L-1 towards the end of the experiment. Increasing the pCO2 reduced the averaged DMS concentrations by 66%and 69%at 10 and 15 °C, respectively, over the duration of the experiment. On the other hand, a 5 °C warming increased DMS concentrations by an average of 240% as compared to in situ temperature, resulting in a positive offset of the adverse pCO2 impact. Significant positive correlations found between bacterial production and concentrations of DMS throughout our experiment point towards temperatureassociated enhancement of bacterial DMSP metabolism as a likely driver of the mitigating effect of warming on the negative impact of acidification on the net production of DMS in the LSLE and potentially the global ocean.Fil: Benard, Robin. Laval University; CanadáFil: Ferreyra, Gustavo Adolfo. Laval University; CanadáFil: Michael, Scarratt. Maurice Lamontagne Institute, Fisheries And Oceans; CanadáFil: Sonia, Michaud. Maurice Lamontagne Institute, Fisheries And Oceans ; CanadáFil: Michel, Starr. Maurice Lamontagne Institute, Fisheries And Oceans; CanadáFil: Alfonso, Mucci. Université Mcgill; CanadáFil: Ferreyra, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Gosselin, Michel. Institut Des Sciences de la Mer de Rimouski; CanadáFil: Tremblay, Jean-Éric. Laval University; CanadáFil: Lizotte, Martine. Laval University; CanadáFil: Yang, Gui Peng. Ocean University; Chin

DNA Fingerprinting of Pearls to Determine Their Origins

We report the first successful extraction of oyster DNA from a pearl and use it to identify the source oyster species for the three major pearl-producing oyster species Pinctada margaritifera, P. maxima and P. radiata. Both mitochondrial and nuclear gene fragments could be PCR-amplified and sequenced. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in the internal transcribed spacer (ITS) region was developed and used to identify 18 pearls of unknown origin. A micro-drilling technique was developed to obtain small amounts of DNA while maintaining the commercial value of the pearls. This DNA fingerprinting method could be used to document the source of historic pearls and will provide more transparency for traders and consumers within the pearl industry

Dimethyl fumarate in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Dimethyl fumarate (DMF) inhibits inflammasome-mediated inflammation and has been proposed as a treatment for patients hospitalised with COVID-19. This randomised, controlled, open-label platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing multiple treatments in patients hospitalised for COVID-19 (NCT04381936, ISRCTN50189673). In this assessment of DMF performed at 27 UK hospitals, adults were randomly allocated (1:1) to either usual standard of care alone or usual standard of care plus DMF. The primary outcome was clinical status on day 5 measured on a seven-point ordinal scale. Secondary outcomes were time to sustained improvement in clinical status, time to discharge, day 5 peripheral blood oxygenation, day 5 C-reactive protein, and improvement in day 10 clinical status. Between 2 March 2021 and 18 November 2021, 713 patients were enroled in the DMF evaluation, of whom 356 were randomly allocated to receive usual care plus DMF, and 357 to usual care alone. 95% of patients received corticosteroids as part of routine care. There was no evidence of a beneficial effect of DMF on clinical status at day 5 (common odds ratio of unfavourable outcome 1.12; 95% CI 0.86-1.47; p = 0.40). There was no significant effect of DMF on any secondary outcome

Dimethyl fumarate in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Dimethyl fumarate (DMF) inhibits inflammasome-mediated inflammation and has been proposed as a treatment for patients hospitalised with COVID-19. This randomised, controlled, open-label platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing multiple treatments in patients hospitalised for COVID-19 (NCT04381936, ISRCTN50189673). In this assessment of DMF performed at 27 UK hospitals, adults were randomly allocated (1:1) to either usual standard of care alone or usual standard of care plus DMF. The primary outcome was clinical status on day 5 measured on a seven-point ordinal scale. Secondary outcomes were time to sustained improvement in clinical status, time to discharge, day 5 peripheral blood oxygenation, day 5 C-reactive protein, and improvement in day 10 clinical status. Between 2 March 2021 and 18 November 2021, 713 patients were enroled in the DMF evaluation, of whom 356 were randomly allocated to receive usual care plus DMF, and 357 to usual care alone. 95% of patients received corticosteroids as part of routine care. There was no evidence of a beneficial effect of DMF on clinical status at day 5 (common odds ratio of unfavourable outcome 1.12; 95% CI 0.86-1.47; p = 0.40). There was no significant effect of DMF on any secondary outcome

Modeling analysis of the effect of iron enrichment on dimethyl sulfide dynamics in the NE Pacific (SERIES experiment)

The large-scale iron enrichment conducted in the NE Pacific during the Subarctic Ecosystem Response to Iron Enrichment Study (SERIES) triggered a phytoplankton bloom dominated successively by nanophytoplankton and large diatoms. During the first 14 days, surface dimethyl sulfide (DMS) levels increased both inside (up to 22 nmol L-1) and outside (up to 19 nmol L-1) the patch, with no consistent Fe effect. Later, DMS concentrations became sixfold lower inside the patch than outside. In this study, we used a DMS budget module embedded in a one-dimensional ocean turbulence model to investigate the contribution of the interacting physical, photochemical, and biological processes to this particular DMS response. Temporal variations in biological net DMS production were reconstructed using an inverse modeling approach. Our results show that short-term (days) variations in both the physical processes (i.e., turbulent mixing and ventilation) and the biological cycling of DMS are needed to explain the time evolution of DMS concentrations both outside and inside the Fe-enriched patch. The biological net DMS production was generally high (up to 0.35 nmol L-1 h-1) and comparable outside and inside the patch during the first 10 days, corresponding to the observed accumulation of DMS inside and outside the patch. Later, it became negative (net DMS biological consumption) inside the patch, suggesting a change in dimethylsulfoniopropionate bacterial metabolism. This study stresses the importance of short-term variations in biological processes and their sensitivity to the physical environment in shaping the DMS response to iron enrichment

PSP-producing dinoflagellate Alexandrium minutum induces valve microclosures in the mussel Mytilus galloprovincialis

7 pages, 4 figures, 1 tableThe saxitoxin-producing dinoflagellate Alexandrium minutum is a well-known microalga that causes paralytic shellfish poisoning (PSP) in many coastal regions of the world. In this study, we measured the valve movements of cultivated mussels Mytilus galloprovincialis feeding on toxic A. minutum (n = 29 mussels, shell length = 67.1 ± 3.2 mm, x̅ ± SD) or a morphologically-similar, but toxin-free phytoplankton, Heterocapsa triquetra (n = 24 mussels, shell length = 68.3 ± 2.9 mm). Phytoplankton inoculations were conducted in three sequential “pulses” intended to increase microalgal cell concentrations in a stepwise manner up to ~5000 cells l−1 over a 9-h period. M. galloprovincialis was connected to a non-invasive valvometry apparatus that concurrently measured the magnitude of valve openness once every 0.1 s. It was found that M. galloprovincialis tended to keep its valves open over the course of the experiment, regardless of the phytoplankton species present in water. Standard valve opening metrics, such as the opening duration and opening amplitude, were not significantly affected by the species of phytoplankton. However, the frequency of brief and partial valve closures (microclosures) was significantly influenced by phytoplankton species (P < .01). M. galloprovincialis subjected to toxic A. minutum exhibited 20.3 ± 0.4 (x̅ ± SEM) microclosures per 3-h pulse period, whereas those exposed to the control H. triquetra exhibited 7.9 ± 0.4 (x̅ ± SEM) microclosures. This response was detectable over the 3 h following the first inoculation pulse that provided a phytoplankton concentration of 1000 cells l−1. Our findings are consistent with growing evidence that bivalves are sensitive to very low concentrations of harmful microalgae. Deploying in situ valvometry sensors with real-time monitoring capabilities may provide an early warning of harmful algal bloomsFinancial support was provided by Fisheries and Oceans Canada and the Spanish government through the Ministerio de Economía y Competitividad (projects AGL2013-45945-R and CTM2016-76146-C3-2-R)Peer reviewe

Impact of anthropogenic pH perturbation on dimethyl sulfide cycling: A peek into the microbial black box

The objective of this study was to assess experimentally the potential impact of anthropogenic pH perturbation (ApHP) on concentrations of dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP), as well as processes governing the microbial cycling of sulfur compounds. A summer planktonic community from surface waters of the Lower St. Lawrence Estuary was monitored in microcosms over 12 days under three pCO(2) targets: 1 x pCO(2) (775 mu atm), 2 x pCO(2) (1,850 mu atm), and 3 x pCO(2) (2,700 mu atm). A mixed phytoplankton bloom comprised of diatoms and unidentified flagellates developed over the course of the experiment. The magnitude and timing of biomass buildup, measured by chlorophyll a concentration, changed in the 3 x pCO(2) treatment, reaching about half the peak chlorophyll a concentration measured in the 1 x pCO(2) treatment, with a 2-day lag. Doubling and tripling the pCO(2) resulted in a 15% and 40% decline in average concentrations of DMS compared to the control. Results from S-35-DMSPd uptake assays indicated that neither concentrations nor microbial scavenging efficiency of dissolved DMSP was affected by increased pCO(2). However, our results show a reduction of the mean microbial yield of DMS by 34% and 61% in the 2 x pCO(2) and 3 x pCO(2) treatments, respectively. DMS concentrations correlated positively with microbial yields of DMS (Spearman's rho = 0.65; P < 0.001), suggesting that the impact of ApHP on concentrations of DMS in diatom-dominated systems may be strongly linked with alterations of the microbial breakdown of dissolved DMSP. Findings from this study provide further empirical evidence of the sensitivity of the microbial DMSP switch under ApHP. Because even small modifications in microbial regulatory mechanisms of DMSP can elicit changes in atmospheric chemistry via dampened efflux of DMS, results from this study may contribute to a better comprehension of Earth's future climate

Tidally induced variations of pH at the head of the Laurentian Channel

International audienceThe head of the Laurentian Channel (LC) is a very dynamic region of exceptional biological richness. To evaluate the impact of freshwater discharge, tidal mixing, and biological activity on the pH of surface waters in this region, a suite of physical and chemical variables was measured throughout the water column over two tidal cycles. The relative contributions to the water column of the four source-water types that converge in this region were evaluated using an optimum multi-parameter algorithm (OMP). Results of the OMP analysis were used to reconstruct the water column properties assuming conservative mixing, and the difference between the model properties and field measurements served to identify factors that control the pH of the surface waters.La tête du chenal Laurentien est une région très dynamique d’une richesse biologique exceptionnelle. Afin d’évaluer l’impact des apports en eaux douces, du mélange tidal, et de l’activité biologique sur le pH des eaux de surface dans cette région, une suite de variables physiques et chimiques a été mesurée dans la colonne d’eau sur deux cycles de marée. La contribution relative des quatre sources d’eau-type qui convergent dans cette région a été évaluée à l’aide d’un algorithme d’optimisation multi-paramétrique (OMP). Les résultats de l’OMP ont été utilisés pour reconstruire les propriétés de la colonne d’eau en assumant un mélange conservateur et la différence entre les propriétés issues du modèle et des mesures effectuées sur le terrain ont servies à identifier les facteurs qui contrôlent le pH des eaux de surface. Les eaux de surface sont généralement sous-saturées par rapport à l’aragonite, surtout à cause de l’intrusion d’eau provenant de l’estuaire fluvial du Saint-Laurent et du fjord du Saguenay. La présence d’une couche intermédiaire froide limite la remontée des eaux profondes, hypoxiques, de faible pH et sous-saturées par rapport à l’aragonite de l’estuaire maritime du Saint-Laurent à des profondeurs de moins de 50 m

St. Lawrence Estuary phytoplankton spring bloom and associated dimehtylsulfide cycling sensitivity to acidification in a microcosm experiment

The potential impact of ocean acidification (OA) on the concentrations of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP), as well as the processes governing the cycling of sulfur compounds by microbial organisms were investigated in a microcosm experiment during summer 2013. A natural planktonic community sourced from the surface waters of the Lower St. Lawrence Estuary (LSLE) was monitored over 12 days under three pCO2 targets: 1 × pCO2 (775 µatm), 2 × pCO2 (1850 µatm), and 3 × pCO2 (2700 µatm). The effects of heightened pCO2 were assessed on phytoplankton biomass, taxonomy and productivity, as well as on DMSP and DMS concentrations and microbial cycling via 35S-DMSPd radioisotope uptake assays. A mixed phytoplankton bloom comprised of the diatoms Chaetoceros spp., Skeletonema costatum, and Thalassiosira spp., as well as unidentified flagellates (2-20 µm) developed over the course of the study period. Concentrations of chlorophyll a (Chl a) peaked on day 6 from an initial 1.26 µg L-1 to 20 ± 4 µg L-1 and 17 ± 1 µg L-1, at 1 × pCO2 and 2 × pCO2, respectively. However, the timing and the magnitude of the biomass build-up were altered in the 3 × pCO2 treatment reaching only 11 ± 4 µg L-1 by day 8 of the experiment. Variations in the concentrations of total DMSP (DMSPt) were largely related to variations in Chl a (Spearman's rho correlation (rs) = 0.77; p < 0.001; n = 61) and peak values of DMSPt were reached consecutively on day 8 in the 1 × pCO2 treatment (264 nmol L-1), on day 10 in the 2 × pCO2 (245 nmol L-1), and on day 12 in the 3 × pCO2 (192 nmol L-1). Concentrations of dissolved DMSP (DMSPd) increased irregularly from 2 ± 1 nmol L-1 to an overall average of 5.2 ± 0.8 nmol L-1 by the end of the experiment; the fluctuations being broadly associated with those observed in DMSPt (rs  = 0.70; p < 0.001; n = 61). Neither concentrations of DMSPd nor the microbial scavenging efficiency of DMSPd (kDMSPd) seemed to be strongly affected by increasing pCO2 suggesting that acidification did not alter the availability and the bacterial uptake of this substrate. However, our results show a reduction of the mean microbial yield of DMS by 34 % and 61 % in the 2 × pCO2 and 3 × pCO2 treatments. Doubling and tripling the pCO2 respectively resulted in a 15 % and 40 % decline in average concentrations of DMS compared to the control. DMS concentrations were positively correlated with microbial yields of DMS (rs = 0.65; p < 0.001; n = 45), suggesting that in diatom-dominated systems, the impact of OA on concentrations of DMS may be strongly linked with alterations of the microbial breakdown of DMSPd. Findings from this study provide the first empirical evidence of the sensitivity of the microbial DMSP switch under OA