Insights into tropical cloud chemistry at Reunion Island (Indian Ocean): results from the BIO-MAÏDO campaign

Abstract. We present here the results obtained during an intensive field campaign conducted in the framework of the French “BIO-MAÏDO” (Bio-physico-chemistry of tropical clouds at Maïdo (Réunion Island): processes and impacts on secondary organic aerosols’ formation) project. This study integrates an exhaustive chemical and microphysical characterization of cloud water obtained in March–April 2019 at Reunion Island (Indian Ocean). Fourteen cloud samples have been collected along the slope of this mountainous island. A comprehensive chemical characterization of these samples is performed, including inorganic ions, metals, oxidants, and organic matter (organic acids, sugars, amino acids, carbonyls, and low-soluble volatile organic compounds (VOCs)). Cloud water presents high molecular complexity with elevated water-soluble organic matter content partly modulated by microphysical cloud properties. As expected, our findings show the presence of compounds of marine origin in cloud water samples (e.g., chloride, sodium) demonstrating ocean–cloud exchanges. However, the non-sea salt fraction of sulphate varies between 38 and 91 %, indicating the presence of other sources. Also, the presence of amino acids and for the first time in cloud waters of sugars, clearly indicates that biological activities contribute to the cloud water chemical composition. A significant variability between events is observed in the dissolved organic content (25.5 ± 18.4 mgC L−1), with levels reaching up to 62 mgC L−1. This variability was not similar for all the measured compounds, suggesting the presence of dissimilar emission sources or production mechanisms. For that, a statistical analysis is performed based on back-trajectory calculations using the CAT (Computing Atmospheric Trajectory Tool) model associated with land cover registry. These investigations reveal that air mass origins and microphysical variables do not fully explain the variability observed in cloud chemical composition, highlighting the complexity of emission sources, multiphasic transfer, and chemical processing in clouds. Additionally, several VOCs (oxygenated and low-soluble VOCs) were analysed in both gas and aqueous phases. Significant levels of biogenic low-soluble VOCs were detected in the aqueous phase, indicating the cloud-terrestrial vegetation exchange. Cloud scavenging of VOCs is assessed and compared to Henry’s law equilibrium to evaluate potential super or sub saturation conditions. The evaluation reveals the supersaturation of low-soluble VOCs from both natural and anthropogenic sources. Our results depict even higher supersaturation of terpenoids, suggesting their importance in the aqueous phase chemistry in highly impacted tropical areas.

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Insights into tropical cloud chemistry in Réunion (Indian Ocean): results from the BIO-MAÏDO campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-22-505-2022 ◽

2022 ◽

Vol 22 (1) ◽

pp. 505-533

Author(s):

Pamela A. Dominutti ◽

Pascal Renard ◽

Mickaël Vaïtilingom ◽

Angelica Bianco ◽

Jean-Luc Baray ◽

...

Keyword(s):

Amino Acids ◽

Organic Matter ◽

Chemical Composition ◽

Aqueous Phase ◽

Cloud Water ◽

Sea Salt ◽

Emission Sources ◽

Air Mass ◽

Low Solubility

Abstract. We present here the results obtained during an intensive field campaign conducted in the framework of the French “BIO-MAÏDO” (Bio-physico-chemistry of tropical clouds at Maïdo (Réunion Island): processes and impacts on secondary organic aerosols' formation) project. This study integrates an exhaustive chemical and microphysical characterization of cloud water obtained in March–April 2019 in Réunion (Indian Ocean). Fourteen cloud samples have been collected along the slope of this mountainous island. Comprehensive chemical characterization of these samples is performed, including inorganic ions, metals, oxidants, and organic matter (organic acids, sugars, amino acids, carbonyls, and low-solubility volatile organic compounds, VOCs). Cloud water presents high molecular complexity with elevated water-soluble organic matter content partly modulated by microphysical cloud properties. As expected, our findings show the presence of compounds of marine origin in cloud water samples (e.g. chloride, sodium) demonstrating ocean–cloud exchanges. Indeed, Na+ and Cl− dominate the inorganic composition contributing to 30 % and 27 %, respectively, to the average total ion content. The strong correlations between these species (r2 = 0.87, p value: < 0.0001) suggest similar air mass origins. However, the average molar Cl-/Na+ ratio (0.85) is lower than the sea-salt one, reflecting a chloride depletion possibly associated with strong acids such as HNO3 and H2SO4. Additionally, the non-sea-salt fraction of sulfate varies between 38 % and 91 %, indicating the presence of other sources. Also, the presence of amino acids and for the first time in cloud waters of sugars clearly indicates that biological activities contribute to the cloud water chemical composition. A significant variability between events is observed in the dissolved organic content (25.5 ± 18.4 mg C L−1), with levels reaching up to 62 mg C L−1. This variability was not similar for all the measured compounds, suggesting the presence of dissimilar emission sources or production mechanisms. For that, a statistical analysis is performed based on back-trajectory calculations using the CAT (Computing Atmospheric Trajectory Tool) model associated with the land cover registry. These investigations reveal that air mass origins and microphysical variables do not fully explain the variability observed in cloud chemical composition, highlighting the complexity of emission sources, multiphasic transfer, and chemical processing in clouds. Even though a minor contribution of VOCs (oxygenated and low-solubility VOCs) to the total dissolved organic carbon (DOC) (0.62 % and 0.06 %, respectively) has been observed, significant levels of biogenic VOC (20 to 180 nmol L−1) were detected in the aqueous phase, indicating the cloud-terrestrial vegetation exchange. Cloud scavenging of VOCs is assessed by measurements obtained in both the gas and aqueous phases and deduced experimental gas-/aqueous-phase partitioning was compared with Henry's law equilibrium to evaluate potential supersaturation or unsaturation conditions. The evaluation reveals the supersaturation of low-solubility VOCs from both natural and anthropogenic sources. Our results depict even higher supersaturation of terpenoids, evidencing a deviation from thermodynamically expected partitioning in the aqueous-phase chemistry in this highly impacted tropical area.

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Isolation and Characterization of 15 Polymorphic Microsatellite Loci for the Barau's Petrel (Pterodroma baraui), an Endangered Endemic of Réunion Island (Indian Ocean)

Waterbirds ◽

10.1675/063.039.0411 ◽

2016 ◽

Vol 39 (4) ◽

pp. 413-416 ◽

Cited By ~ 1

Author(s):

Daniel K. Danckwerts ◽

Samantha Corré ◽

Patrick Pinet ◽

Matthieu Le Corre ◽

Laurence Humeau

Keyword(s):

Indian Ocean ◽

Microsatellite Loci ◽

Reunion Island ◽

Isolation And Characterization ◽

Réunion Island ◽

Polymorphic Microsatellite

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Investigation of a leptospirosis outbreak in triathlon participants, Réunion Island, 2013

Epidemiology and Infection ◽

10.1017/s0950268815001740 ◽

2015 ◽

Vol 144 (3) ◽

pp. 661-669 ◽

Cited By ~ 12

Author(s):

F. PAGÈS ◽

S. LARRIEU ◽

J. SIMOES ◽

P. LENABAT ◽

B. KURTKOWIAK ◽

...

Keyword(s):

Indian Ocean ◽

Attack Rate ◽

Reunion Island ◽

Epidemiological Investigation ◽

Infection Rates ◽

Serological Tests ◽

Partial Sequencing ◽

16S Gene ◽

Réunion Island

SUMMARYWe report herein the investigation of a leptospirosis outbreak occurring in triathlon competitors on Réunion Island, Indian Ocean. All participants were contacted by phone or email and answered a questionnaire. Detection and molecular characterization of pathogenicLeptospirawas conducted in inpatients and in rodents trapped at the vicinity of the event. Of the 160 athletes competing, 101 (63·1%) agreed to participate in the study. Leptospirosis was biologically confirmed for 9/10 suspected cases either by real-time PCR or serological tests (MAT or ELISA). The total attack rate, children's attack rate, swimmers’ attack rate, and the attack rate in adult swimmers were respectively estimated at 8·1% [95% confidence interval (CI) 4·3–14·7], 0%, 12·7% (95% CI 6·8–22·4) and 23·1% (95% CI 12·6–33·8). Leptospirosis cases reported significantly more wounds [risk ratio (RR) 4·5, 95% CI 1·6–13], wore complete neoprene suits less often (RR 4·3, 95% CI 1·3–14·5) and were most frequently unlicensed (RR 6·6, 95% CI 2·9–14·8). The epidemiological investigation supported that some measures such as the use of neoprene suits proved efficient in protecting swimmers against infection. PCR detection in rats revealed highLeptospirainfection rates. Partial sequencing of the 16S gene and serology on both human and animal samples strongly suggests that rats were the main contaminators and were likely at the origin of the infection in humans.

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Hypotrachyna altorumsp. nov., a New Lichen from the Cloud Forests of Réunion Island, Indian Ocean

Cryptogamie Mycologie ◽

10.7872/crym.v33.iss2.2012.203 ◽

2012 ◽

Vol 33 (2) ◽

pp. 203-212 ◽

Cited By ~ 3

Author(s):

Didier Masson

Keyword(s):

Indian Ocean ◽

Reunion Island ◽

Cloud Forests ◽

Réunion Island

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Evaluation of WRF-DART (ARW v3.9.1.1 and DART Manhattan release) multiphase cloud water path assimilation for short-term solar irradiance forecasting in a tropical environment

Geoscientific Model Development ◽

10.5194/gmd-12-3939-2019 ◽

2019 ◽

Vol 12 (9) ◽

pp. 3939-3954

Author(s):

Frederik Kurzrock ◽

Hannah Nguyen ◽

Jerome Sauer ◽

Fabrice Chane Ming ◽

Sylvain Cros ◽

...

Keyword(s):

Data Assimilation ◽

Weather Prediction ◽

Cloud Water ◽

Specific Humidity ◽

Reunion Island ◽

Short Term ◽

Water Path ◽

Réunion Island ◽

Cloud Water Path ◽

The Impact

Abstract. Numerical weather prediction models tend to underestimate cloud presence and therefore often overestimate global horizontal irradiance (GHI). The assimilation of cloud water path (CWP) retrievals from geostationary satellites using an ensemble Kalman filter (EnKF) led to improved short-term GHI forecasts of the Weather Research and Forecasting (WRF) model in midlatitudes in case studies. An evaluation of the method under tropical conditions and a quantification of this improvement for study periods of more than a few days are still missing. This paper focuses on the assimilation of CWP retrievals in three phases (ice, supercooled, and liquid) in a 6-hourly cycling procedure and on the impact of this method on short-term forecasts of GHI for Réunion Island, a tropical island in the southwest Indian Ocean. The multilayer gridded cloud properties of NASA Langley's Satellite ClOud and Radiation Property retrieval System (SatCORPS) are assimilated using the EnKF of the Data Assimilation Research Testbed (DART) Manhattan release (revision 12002) and the advanced research WRF (ARW) v3.9.1.1. The ability of the method to improve cloud analyses and GHI forecasts is demonstrated, and a comparison using independent radiosoundings shows a reduction of specific humidity bias in the WRF analyses, especially in the low and middle troposphere. Ground-based GHI observations at 12 sites on Réunion Island are used to quantify the impact of CWP DA. Over a total of 44 d during austral summertime, when averaged over all sites, CWP data assimilation has a positive impact on GHI forecasts for all lead times between 5 and 14 h. Root mean square error and mean absolute error are reduced by 4 % and 3 %, respectively.

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Bat coronavirus phylogeography in the Western Indian Ocean

10.1101/742866 ◽

2019 ◽

Cited By ~ 1

Author(s):

Léa Joffrin ◽

Steven M. Goodman ◽

David A. Wilkinson ◽

Beza Ramasindrazana ◽

Erwan Lagadec ◽

...

Keyword(s):

Indian Ocean ◽

Phylogenetic Analyses ◽

Strong Association ◽

Western Indian Ocean ◽

Reunion Island ◽

High Genetic Diversity ◽

Soil Fertilization ◽

Réunion Island ◽

History Of ◽

Bat Coronavirus

AbstractBats provide key ecosystem services such as crop pest regulation, pollination, seed dispersal, and soil fertilization. Bats are also major hosts for biological agents responsible for zoonoses, such as coronaviruses (CoVs). The islands of the Western Indian Ocean are identified as a major biodiversity hotspot, with more than 50 bat species. In this study, we tested 1,013 bats belonging to 36 species from Mozambique, Madagascar, Mauritius, Mayotte, Reunion Island and Seychelles, based on molecular screening and partial sequencing of the RNA-dependent RNA polymerase gene. In total, 88 bats (8.7%) tested positive for coronaviruses, with higher prevalence in Mozambican bats (20.5% ± 4.9%) as compared to those sampled on islands (4.5% ± 1.5%). Phylogenetic analyses revealed a large diversity of α- and β-CoVs and a strong signal of co-evolution between CoVs and their bat host species, with limited evidence for host-switching, except for bat species sharing day roost sites.ImportanceThis is the first study to report the presence of coronaviruses (CoVs) in bats in Mayotte, Mozambique and Reunion Island, and in insectivorous bats in Madagascar. Eight percent of the tested bats were positive for CoVs, with higher prevalence in continental Africa than on islands. A high genetic diversity of α- and β-CoVs was found, with strong association between bat host and virus phylogenies, supporting a long history of co-evolution between bats and their associated CoVs in the Western Indian Ocean. These results highlight that strong variation between islands does exist and is associated with the composition of the bat species community on each island. Future studies should investigate whether CoVs detected in these bats have a potential for spillover in other hosts.

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