Demographic consequences of heavy metals and persistent organic pollutants in a vulnerable long-lived bird, the wandering albatross

International audienceSeabirds are top predators of the marine environment that accumulate contaminants over a long life-span. Chronic exposure to pollutants is thought to compromise survival rate and long-term reproductive outputs in these long-lived organisms, thus inducing population decline. However, the demographic consequences of contaminant exposure are largely theoretical because of the dearth of long-term datasets. This study aims to test whether adult survival rate, return to the colony and long-term breeding performance were related to blood mercury (Hg), cadmium (Cd) and persistent organic pollutants (POPs), by using a capture–mark–recapture dataset on the vulnerable wandering albatross Diomedea exulans. We did not find evidence for any effect of contaminants on adult survival probability. However, blood Hg and POPs negatively impacted long-term breeding probability, hatching and fledging probabilities. The proximate mechanisms underlying these deleterious effects are likely multifaceted, through physiological perturbations and interactions with reproductive costs. Using matrix population models, we projected a demographic decline in response to an increase in Hg or POPs concentrations. This decline in population growth rate could be exacerbated by other anthropogenic perturbations, such as climate change, disease and fishery bycatch. This study gives a new dimension to the overall picture of environmental threats to wildlife populations

To breed or not to breed: Endocrine response to mercury contamination by an Arctic seabird

Mercury, a ubiquitous toxic element, is known to alter expression of sex steroids and to impair reproduction across vertebrates but the mechanisms underlying these effects are not clearly identified. We examined whether contamination by mercury predicts the probability to skip reproduction in black-legged kittiwakes (Rissa tridactyla) from Svalbard. We also manipulated the endocrine system to investigate the mechanism underlying this relationship. During the pre-laying period, we injected exogenous GnRH (gonadotropin-releasing hormone) to test the ability of the pituitary to release luteinizing hormone (LH, a key hormone for the release of sex steroids and hence breeding) in relation to mercury burden. Birds that skipped reproduction had significantly higher mercury concentration in blood than breeders. Endocrine profiles of these birds also varied based on breeding status (breeders versus non-breeders), mercury contamination and sex. Specifically, in skippers (birds that did not breed), baseline LH decreased with increasing mercury concentration in males, whereas it increased in females. GnRH-induced LH levels increased with increasing mercury concentration in both sexes. These results suggest that mercury contamination may disrupt GnRH input to the pituitary. Thus, high mercury concentration could affect the ability of long-lived birds to modulate their reproductive effort (skipping or breeding) according to ongoing environmental changes in the Arctic, thereby impacting population dynamics

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Mécanismes hormonaux impliqués dans la phénologie de la reproduction chez les oiseaux marins polaires

Breeding at the right time is a key-component of fitness, and requires flexible responses to environmental conditions and physiological state. However, the proximate mechanisms underlying this pattern remain poorly understood. This doctoral research aims to explore the hormonal mechanisms that mediate the onset of egg-laying in two polar seabirds, the blacklegged kittiwake and the snow petrel. First of all, a food-related stress during the pre-laying period allowed us to associate a late-breeding year with high levels of corticosterone (stress hormone) and with low levels of LH (luteinizing hormone that triggers reproduction). Moreover, an experimentally delayed breeding promoted an accentuated stress response, a decline of parental effort, and a high reproductive failure. Descriptive and experimental approaches supported the role of corticosterone in the individual adjustment of egg-laying dates and in the non-breeding decision, through the inhibition of LH release. However, this functional action of corticosterone differed between sex and between species. At last, we investigated the effects of age (7-45 years old) and senescence on the dynamics of corticosterone and LH, since very young and very old birds did not breed or bred late in the season. We discussed the possible hormonal orchestration of reproductive phenology, as an interaction between environmental stress and individual state, in the theoretical framework of evolutionary strategies.La phénologie de la reproduction a des conséquences majeures sur la valeur sélective, et témoigne de la flexibilité des individus à répondre aux conditions environnementales, en fonction de leur état physiologique. Les mécanismes proximaux sous-jacents restent cependant très peu connus. Ce doctorat vise à explorer les processus hormonaux impliqués dans l'ajustement de la date de ponte chez deux oiseaux marins polaires, la mouette tridactyle et le pétrel des neiges. Dans un premier temps, une contrainte nutritionnelle en période prénuptiale nous a permis d'associer une année tardive à une élévation des taux de corticostérone (hormone de stress) et à une diminution des taux de LH (hormone lutéinisante, déclencheur principal de la reproduction). Par ailleurs, un retard expérimental de la reproduction provoque une sensibilité accrue au stress, un déclin de la motivation parentale et un échec reproducteur. Grâce à des approches descriptives et expérimentales, nous avons ensuite pu identifier le rôle de la corticostérone sur l'ajustement individuel des dates de ponte et sur l'abstention de la reproduction, via l'inhibition de la sécrétion de LH. Ce mode d'action fonctionnelle est toutefois à nuancer entre mâles et femelles et entre espèces étudiées. Enfin, sachant que les très jeunes et les très vieux oiseaux pondent tard dans la saison, voire s'abstiennent de se reproduire, nous avons décrit les effets de l'âge (7-45 ans) et de la sénescence sur la dynamique de la corticostérone et de la LH. À la lumière de ces résultats, nous discutons de la possible orchestration hormonale de la phénologie, au carrefour entre le stress environnemental et l'état individuel, dans le cadre théorique des stratégies évolutives

Imprégnation de la faune sauvage par les micropolluants :Causes et conséquences sur les individus et les populations

L’exposition à de multiples polluants constitue l’une des pressions anthropiques qui menacent la biodiversité. Appréhender l’imprégnation de la faune sauvage et les dommages potentiels est un défi majeur en éotoxicologie, en raison de la complexité des processus qui gouvernent le devenir et les effets des polluants dans les organismes. Mes travaux de recherche visent, d’une part, à mieux caractériser les transferts de micropolluants (mercure, Polychlorobiphényles (PCBs), pesticides organochlorés, Hydrocarbures Aromatiques Polycycliques (HAPs), phtalates, insecticides pyréthrinoïdes), ainsi que leurs métabolites dans les réseaux trophiques marins polaires et dulçaquicoles tempérés, des proies aux prédateurs, mais aussi des hôtes aux parasites. Les voies d’exposition environnementale et les processus de métabolisation ont été explorés, ainsi que les effets de l’âge, de l’habitat, de l’écologie trophique et du parasitisme sur les niveaux de contamination des poissons. D’autre part, les effets des micropolluants et de leurs métabolites ont été évalués à différentes échelles biologiques. Au niveau physiologique, seuls quelques composés, malgré leurs niveaux relativement faibles, accélèrent le vieillissement des individus et perturbent la sécrétion d’hormones et l’expression de comportement reproducteur. En ce qui concerne les traits d’histoire de vie, l’utilisation de jeux de données à long-terme et de modèles de capture-marquage-recapture ont permis de montrer que les taux élevés de mercure, PCBs et pesticides organochlorés, en particulier l’oxychlordane et le mirex, peuvent compromettre les performances de reproduction à long terme des oiseaux marins en Arctique et en Antarctique, voire même diminuer les taux de survie des adultes. Ces résultats illustrent notamment de fortes disparités entre espèces phylogénétiquement proches et entre mâles et femelles. A l’échelle des populations, il a été possible de projeter des déclins démographiques avec une exposition croissante aux micropolluants. Dans un contexte de stress multiples, ces travaux soulignent que certaines perturbations environnementales amplifient ou au contraire, atténuent les effets des polluants, réitérant l’importance de conduire des études écotoxicologiques en milieux naturels

Narrower isotopic niche size in fish infected by the intestinal parasite <i>Pomphorhynchus</i> sp. compared to uninfected ones

International audienceExamples of parasite-related effects on intermediate crustacean hosts are numerous but their ecological consequences on their vertebrate hosts are scarce. Here, we address the role of macroparasite infections on the trophic niche structure of definitive hosts and its potential physiological consequences using wild fish populations infected with an acantochephalan parasite Pomphorhynchus sp., a trophically transmitted intestinal worm. Infected and uninfected fish were sampled from six populations on the Marne River, France and the prevalence of intestinal parasites in the host populations ranged from 50% to 90%. Although the isotopic ratios (δ 13 C and δ 15 N) did not differ between infected and uninfected fish, we found a consistent pattern of isotopic niche size being considerably smaller in infected hosts when compared with noninfected ones. This was not explained by interindividual differences in intrinsic factors such as length/age or body condition between infected and uninfected fish. These results suggest a potential niche specialization of infected fish, which did not impair their energetic status

Determination of glyphosate and AMPA in fish bile from the Marne River, France

International audienceGlyphosate is a widely used herbicide. In France, it is used during intercultural operations and to control weeds in non-agricultural areas. Glyphosate and AMPA (its main degradation product) can reach high concentrations in rivers, especially in the Seine basin including the Paris suburb (France). Although it is not bioaccumulative, the associated use of surfactants in pesticide formulations allows better assimilation in biological tissues. The aim of our study was first to develop a method to assess glyphosate and AMPA levels in biological tissues and then to determine the contamination of an freshwater fish, the European chub (Squalius cephalus) by glyphosate and AMPA. Fish were fished in the Marne River (a tributary of the Seine River situated in the East part of Paris) at 4 sites characteristic of agricultural and urban areas. Water was also sampled for analysis to compare sites contamination. Bile is an ideal material to identify metabolites of pollutants. This biological fluid was taken directly from the gallbladder with a syringe on freshly euthanized chub and frozen for further analysis. Then, 100μL of bile was taken and 500μL of internal standard (13C-Glyphosate and 13C-AMPA) were added before extraction with milliQ water (5mL) and ultrasonic method for 30 minutes. The extract was then derivatizated (FMOC-Cl) and concentrated on SPE OASIS HLB cartridge (60cc) before LC MS MS analysis. Preliminary tests were performed to establish and validate the protocol and to find the lowest limit of quantification and the best reproducibility. Results showed that glyphosate is detected in a fish sample coming from the most contaminated site by AMPA. This suggests that glyphosate is assimilated in fish and is still detectable after glyphosate has been degraded to AMPA in the water river. Glyphosate content in fish could be an indicator of environmental contamination. Further developments are needed to validate the protocol and complete the study with other organs than bile

Fish from urban rivers and with high pollutant levels have shorter telomeres

International audienceEnvironmental pressures, such as urbanization and exposure to pollutants may jeopardize survival of free-living animals. Yet, much remains to be known about physiological and ecological responses to currently-released pollutants, especially in wild vertebrate ectotherms. We tested the effect of urbanization and pollution (phthalates, organochlorine and pyrethroid pesticides, polychlorobiphenyls, polybromodiphenylethers, polycyclic aromatic hydrocarbons, and some of their metabolites) on telomere length, a suggested biomarker of life expectancy, in the European chub, Squalius cephalus, from urban and agricultural rivers of the Marne hydrographic network, France. We showed that telomere length was reduced in chub from urban rivers. Moreover, among the wide range of anthropogenic contaminants investigated, high levels of phthalate metabolites in liver were associated with shorter telomeres. This study suggests that urbanization and chemical pollution may compromise survival of wild fish, by accelerating telomere attrition

Monitoring freshwater fish communities in large rivers using environmental DNA (eDNA) metabarcoding and a long‐term electrofishing survey (1990-2018)

International audienceMonitoring freshwater fish communities in a large human-impacted river is a challenging task. The structure of fish assemblages has been monitored yearly in the Marne and the Seine Rivers, across the Paris conurbation, France, using traditional electrofishing (EF) surveys since 1990, in accordance with the European Water Framework Directive. in addition, metabarcoding of DNA extracted from environmental samples (eDNA) was concomitantly conducted in nine sampling sites in 2017 and in 2018 to compare the estimates of species richness and relative abundance among three methods: annual, long-term EF monitoring and eDNA. The present study confirms better detection of fish species using eDNA compared to annual EF. eDNA metabarcoding was also more efficient for species detection than a 3–6-year EF survey but was similar or less efficient than a long-term EF survey of 14 years of monitoring. In addition, the numbers of reads per species relative to the total number of reads significantly increased with (a) increasing relative abundance (relative percentage of individuals caught per species) and (b) increasing number of years that a fish species was detected during the 2000–2018 period. These results suggest that eDNA could reflect local population persistence