Contribution of N₂O emissions to the atmosphere from Indian monsoonal estuaries

Estuaries are known to contribute a significant amount of nitrous oxide (N2O) to the atmosphere; however, the contribution from the Indian estuaries is unknown. We made an attempt to estimate emissions of N2O from the Indian estuaries by collecting samples from 28 major and minor estuaries along the Indian coast during the wet and dry periods. The N2O was mostly saturated in all measured Indian estuaries during the study period (72–631 %), with exceptionally high saturation in the Ponniyaar estuary (5902%) during the wet period. The N2O saturation displayed a strong relation with dissolved inorganic nitrogen (DIN; nitrate+nitrite and ammonium), ammonium and dissolved oxygen saturation, suggesting that nitrification is the major source of N2O in the Indian estuaries. The negative relation between salinity and N2O saturation suggests inner estuaries are a strong source compared to outer estuaries. The annual mean N2O saturation (204 ± 137%) and fluxes (1.3 μmol N2O m−2 d−1) in the Indian estuaries were significantly less than European estuaries (271% and ∼2.7 μmol N2O m−2 d−1, respectively). The estimation of flux of N2O from the European estuaries was also biased due to the inclusion of an exceptionally high supersaturation value from a small UK estuary, Colne (2645%). However, low N2O saturation and fluxes in the Indian estuaries were related to mean low concentration of DIN that led to low nitrification rates compared to world estuaries. Despite India ranking second in artificial fertilizers use, high flushing rates during the wet period reduce residence time leading to less modification within the estuary

A study on inorganic carbon components in the Andaman Sea during the post monsoon season

Extensive data have been collected on the carbon dioxide system during the post monsoon season in the eastern Bay of Bengal and the Andaman Sea of the northeastern Indian Ocean. The vertical distribution of temperature and salinity in the eastern Bay of Bengal were similar to that in the Andaman Sea down to 700–800 m. Below 1200 m depth the salinity remained constant at 34.90 in the Andaman Sea whereas it decreased to 34.80 in the eastern Bay of Bengal. On the other hand, deep waters (> 1200 m) of the Andaman Sea were warmer than those of the Bay of Bengal by approximately 2°C. Dissolved oxygen concentrations in the subsurface waters were higher in the Andaman Sea than in the central Bay of Bengal and Arabian Sea due to lower rates of regeneration. Total alkalinity, and pCO₂ showed similar distribution patterns both in the eastern Bay of Bengal and the Andaman Sea up to a depth of 1000–1200 m. Below this depth, their concentrations were higher in the latter than compared to former due to warmer waters. Carbonate saturation depth with respect to aragonite was shallow (approximately 300 m) in the Andaman Sea whereas deeper waters were found to be under saturated with respect to calcite

Stable Isotopic and Chemical Characteristics of Bulk Aerosols during Winter and Summer Season at a Station in Western Coast of India (Goa)

We measured stable isotopic and chemical characteristics of bulk aerosols collected at a coastal station in western India (Goa) between December 2009 and January 2011, to characterize lower tropospheric atmospheric conditions and their influence on particle chemistry during winter and summer seasons. Marked differences were observed in terms of sources and chemical compositions of bulk aerosols. The delta N-15(TN) values of winter aerosols (10.8 +/- 2.2 parts per thousand, n = 10) indicate biomass burning contributions in the carbonaceous fraction, while significantly depleted delta N-15(TN) values of summer aerosols (6.2 +/- 2.3 parts per thousand, n = 12) hints incorporation of marine N species. The delta S-34(TS) showed depleted values during winter (5.0 +/- 1.0 parts per thousand, n = 10), which closely matched with those of typical urban polluted environments, while summer aerosols showed a systematic enrichment of delta S-34(TS) (up to similar to 14 parts per thousand with average value 9.0 +/- 2.8 parts per thousand, n = 13); possibly due to incorporation of volatile dimethyl sulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) emitted from the adjacent Arabian Sea. Likewise, delta C-13(TOC) values showed similar to 2 parts per thousand enrichment in winter aerosols (-24.8 +/- 0.4 parts per thousand, n = 10) with respect to those of summer values, indicating presence of bio-fuel and coal burning contributions in carbonaceous fraction of winter aerosols. We also measured major ions (Na+, K+, Mg++, Ca++, NH4 (+), Cl-, Br-, NO3-, SO4-2) in water soluble fraction of aerosols to understand winter/summer changes in the atmospheric chemistry over this coastal area. This is the first ever dataset on triple isotopic characteristics of bulk aerosols at a coastal location of India showing signatures of continental bio-mass/biofuel burning influences during winter, whereas marine inventories (e.g., sea salt, DMS and mineral dust) appear to dominate chemical composition of summer aerosols

Global coastal groundwater and subterranean estuary nutrients

These data were compiled from original and published datasets of coastal groundwater / subterranean estuary research efforts along global coastline (sites within 1km of shoreline). The dataset includes sampling site names, locations, original sample information, sample depth, temperature, salinity, dissolved nitrogen concentrations, and dissolved phosphorus concentrations. The data source or curator is also included in the dataset

Surface Ocean CO2 Atlas (SOCAT) V2

The Surface Ocean CO2 Atlas (SOCAT), an activity of the international marine carbon research community, provides access to synthesis and gridded fCO2 (fugacity of carbon dioxide) products for the surface oceans. Version 2 of SOCAT is an update of the previous release (version 1) with more data (increased from 6.3 million to 10.1 million surface water fCO2 values) and extended data coverage (from 1968-2007 to 1968-2011). The quality control criteria, while identical in both versions, have been applied more strictly in version 2 than in version 1. The SOCAT website (http://www.socat.info/) has links to quality control comments, metadata, individual data set files, and synthesis and gridded data products. Interactive online tools allow visitors to explore the richness of the data. Applications of SOCAT include process studies, quantification of the ocean carbon sink and its spatial, seasonal, year-to-year and longerterm variation, as well as initialisation or validation of ocean carbon models and coupled climate-carbon models

Base de données mondiale des diazotrophes océaniques version 2 et estimation élevée de la fixation de N 2 dans l'océan mondial

International audienceAbstract. Marine diazotrophs convert dinitrogen (N2) gas into bioavailable nitrogen (N), supporting life in the global ocean. In 2012, the first version of the global oceanic diazotroph database (version 1) was published. Here, we present an updated version of the database (version 2), significantly increasing the number of in situ diazotrophic measurements from 13 565 to 55 286. Data points for N2 fixation rates, diazotrophic cell abundance, and nifH gene copy abundance have increased by 184 %, 86 %, and 809 %, respectively. Version 2 includes two new data sheets for the nifH gene copy abundance of non-cyanobacterial diazotrophs and cell-specific N2 fixation rates. The measurements of N2 fixation rates approximately follow a log-normal distribution in both version 1 and version 2. However, version 2 considerably extends both the left and right tails of the distribution. Consequently, when estimating global oceanic N2 fixation rates using the geometric means of different ocean basins, version 1 and version 2 yield similar rates (43–57 versus 45–63 Tg N yr−1; ranges based on one geometric standard error). In contrast, when using arithmetic means, version 2 suggests a significantly higher rate of 223±30 Tg N yr−1 (mean ± standard error; same hereafter) compared to version 1 (74±7 Tg N yr−1). Specifically, substantial rate increases are estimated for the South Pacific Ocean (88±23 versus 20±2 Tg N yr−1), primarily driven by measurements in the southwestern subtropics, and for the North Atlantic Ocean (40±9 versus 10±2 Tg N yr−1). Moreover, version 2 estimates the N2 fixation rate in the Indian Ocean to be 35±14 Tg N yr−1, which could not be estimated using version 1 due to limited data availability. Furthermore, a comparison of N2 fixation rates obtained through different measurement methods at the same months, locations, and depths reveals that the conventional 15N2 bubble method yields lower rates in 69 % cases compared to the new 15N2 dissolution method. This updated version of the database can facilitate future studies in marine ecology and biogeochemistry. The database is stored at the Figshare repository (https://doi.org/10.6084/m9.figshare.21677687; Shao et al., 2022).Résumé. Les diazotrophes marins convertissent le diazote (N2) gazeux en azote (N) biodisponible, ce qui favorise la vie dans l'océan mondial. En 2012, la première version de la base de données mondiale des diazotrophes océaniques (version 1) a été publiée. Nous présentons ici une version actualisée de la base de données (version 2), augmentant de manière significative le nombre de mesures diazotrophiques in situ de 13 565 à 55 286. Les points de données pour les taux de fixation de N2, l'abondance des cellules diazotrophes et l'abondance des copies du gène nifH ont augmenté de 184 %, 86 % et 809 %, respectivement. La version 2 comprend deux nouvelles fiches de données pour l'abondance des copies du gène nifH des diazotrophes non cyanobactériens et les taux de fixation de N2 spécifiques aux cellules. Les mesures des taux de fixation N2 suivent approximativement une distribution log-normale dans les versions 1 et 2. Cependant, la version 2 étend considérablement les queues gauche et droite de la distribution. Par conséquent, lorsque l'on estime les taux de fixation de N2 dans l'océan mondial en utilisant les moyennes géométriques des différents bassins océaniques, la version 1 et la version 2 donnent des taux similaires (43-57 contre 45-63 Tg N an-1 ; fourchettes basées sur une erreur géométrique type). En revanche, lorsque l'on utilise les moyennes arithmétiques, la version 2 suggère un taux significativement plus élevé de 223±30 Tg N an-1 (moyenne ± erreur standard ; idem ci-après) par rapport à la version 1 (74±7 Tg N an-1). Plus précisément, des augmentations substantielles du taux sont estimées pour l'océan Pacifique Sud (88±23 contre 20±2 Tg N an-1), principalement grâce aux mesures effectuées dans les régions subtropicales du sud-ouest, et pour l'océan Atlantique Nord (40±9 contre 10±2 Tg N an-1). En outre, la version 2 estime le taux de fixation de N2 dans l'océan Indien à 35±14 Tg N an-1, ce qui n'a pas pu être estimé avec la version 1 en raison de la disponibilité limitée des données. En outre, une comparaison des taux de fixation de N2 obtenus par différentes méthodes de mesure aux mêmes mois, lieux et profondeurs révèle que la méthode conventionnelle des bulles de 15N2 donne des taux inférieurs dans 69 % des cas par rapport à la nouvelle méthode de dissolution de 15N2. Cette version actualisée de la base de données peut faciliter les études futures en écologie marine et en biogéochimie. La base de données est stockée dans le dépôt Figshare (https://doi.org/10.6084/m9.figshare.21677687 ; Shao et al., 2022)

Global oceanic diazotroph database version 2 and elevated estimate of global oceanic N2 fixation

Marine diazotrophs convert dinitrogen (N2) gas into bioavailable nitrogen (N), supporting life in the global ocean. In 2012, the first version of the global oceanic diazotroph database (version 1) was published. Here, we present an updated version of the database (version 2), significantly increasing the number of in situ diazotrophic measurements from 13 565 to 55 286. Data points for N2 fixation rates, diazotrophic cell abundance, and nifH gene copy abundance have increased by 184 %, 86 %, and 809 %, respectively. Version 2 includes two new data sheets for the nifH gene copy abundance of non-cyanobacterial diazotrophs and cell-specific N2 fixation rates. The measurements of N2 fixation rates approximately follow a log-normal distribution in both version 1 and version 2. However, version 2 considerably extends both the left and right tails of the distribution. Consequently, when estimating global oceanic N2 fixation rates using the geometric means of different ocean basins, version 1 and version 2 yield similar rates (43–57 versus 45–63 Tg N yr−1; ranges based on one geometric standard error). In contrast, when using arithmetic means, version 2 suggests a significantly higher rate of 223±30 Tg N yr−1 (mean ± standard error; same hereafter) compared to version 1 (74±7 Tg N yr−1). Specifically, substantial rate increases are estimated for the South Pacific Ocean (88±23 versus 20±2 Tg N yr−1), primarily driven by measurements in the southwestern subtropics, and for the North Atlantic Ocean (40±9 versus 10±2 Tg N yr−1). Moreover, version 2 estimates the N2 fixation rate in the Indian Ocean to be 35±14 Tg N yr−1, which could not be estimated using version 1 due to limited data availability. Furthermore, a comparison of N2 fixation rates obtained through different measurement methods at the same months, locations, and depths reveals that the conventional 15N2 bubble method yields lower rates in 69 % cases compared to the new 15N2 dissolution method. This updated version of the database can facilitate future studies in marine ecology and biogeochemistry. The database is stored at the Figshare repository (https://doi.org/10.6084/m9.figshare.21677687; Shao et al., 2022)