Historical mass balance of cadmium decontamination trends in a major European continent-ocean transition system: Case study of the Gironde Estuary
Despite the effective remediation efforts following the end of the metallurgic activity thirty years ago upstream the Lot River watershed, the levels of cadmium (Cd) accumulated in wild oysters from the downstream Gironde Estuary still exceed nowadays the admissible human consumption limit (5 mg/kg, d.w.). The main goal of this work is to quantify the role of sediments as long-term intra-estuarine sources or sinks of Cd and the transport of this contaminant towards the estuary mouth taking as case study the example of the highly turbid Gironde Estuary. The original estimation for the annual net fluxes of the suspended particulate matter (FnetSPMyear) and particulate Cd (FnetCdpyear) presented in this work between 1990 and 2020 indicates that 80% of the Cd discharged into the ocean is in dissolved form (Cdd). The values of FnetCdpyear vary proportionally to those of FnetSPMyear and ranged between 0.1 and 1.4 t/y, with a ten-year average decreasing from 0.8 to 0.6 t/y for the past 30 years. The differences between ten-year total (Cdp + Cdd) gross and net fluxes show that Cd has effectively been stored in estuarine sediments. This Cd storage was of about 43, 22 and 13 t for the 1990s, 2000s and 2010s, respectively. However, during years of low gross fluxes, estuarine sediments act as additional, secondary sources of bio-available/dissolved Cd into the water column, potentially relating to the continued observations of high Cd concentrations in wild oysters at the estuary mouth. In addition to the natural solubility of Cdp along the salinity and turbidity gradients of the estuary, natural and anthropogenic remobilization of bottom sediment particles further contribute to its mobilization from the particle phase, along with other numerous inorganic/organic pollutants. The mass balances presented in this work could support a new sediment management policy potentially more beneficial to the estuarine ecosystem.
(Marine Environmental Research. vol. 176, n° 0141-1136, 01/04/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Asian-Australian monsoon evolution over the last millennium linked to ENSO in composite stalagmite δ18O records
The Asian-Australian monsoon (AAM) system distinctly influences global climate. However, the linkage between ENSO (El Niño–Southern Oscillation) and AAM is still poorly understood over the last millennium. Here, we combined stalagmite δ18O (δ18Os) records with exceptionally high-resolution and high-precision chronologies to demonstrate a tight remote coupling between AAM and tropical ocean hydrology on the multi-year, decadal, and centennial timescales. Our results reveal that (1) There is a significant negative correlation between the multi-year weighted average precipitation δ18O (δ18Oaw) from the AAM and Southern Oscillation Index (SOI), providing a modern analogous coupling for linking stalagmite δ18O (δ18Os) and ENSO over the past 100 years. (2) Over the last millennium, the integrated δ18Os record exhibit positive excursions during the Little Ice Age (LIA), marked by a tendency for more El Niño-like state conditions in the tropical Pacific, which is consistent in SST-gradient ENSO reconstruction but different to precipitation reconstruction. (3) Wavelet and power spectrum analysis for the integrated δ18Os record in the AAM region show that there is a significant multi-year periodicity (2.2, 2.8, 3.5, 4.6 yr), conceding with the ENSO cycle (2–7 yr), whereas, some multi-decadal and centennial cycles (10.1, 17, 28.6, 52.7, 143 yr) are significant too. We provide evidence from instrumental and paleocliamte datasets (GNIP and NOAA) and propose a possible “circulation effect” mechanism responsible for variations of δ18Os in the East Asian Monsoon (EAM) and Australian Monsoon (AM) region over the last millennium.
(Quaternary Science Reviews. vol. 281, n° 0277-3791, 01/04/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Pesticide toxicity towards microalgae increases with environmental mixture complexity
Effect-directed analysis (EDA) aims at identifying the compound(s) responsible for toxicity in a complex environmental sample where several dozens of contaminants can be present. In this study, we used an environmental mixture extracted from the Polar Organic Chemical Integrative Sampler (POCIS) previously immersed downstream a landfill (River Ponteils, South West France), to perform an EDA approach using a microalgal bioassay based on the photosynthetic capacities of diatom (Nitzschia palea) cultures. Adverse effects on photosynthetic capacities were recorded when algae were exposed to the entire POCIS extract (> 85% inhibition at the highest concentration tested). This result was coherent with the detection of diuron and isoproturon, which were the 2 most concentrated herbicides in the extract. However, the EDA process did not allow pointing out the specific compound(s) responsible for the observed toxicity but rather suggested that multiple compounds were involved in the overall toxicity and caused mixture effects.
(Environmental Science and Pollution Research. vol. 29, n° 0944-1344, pp. 29368-29381, 01/04/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE
ESCROpath , a Bayesian mixing model to quantify diets and trophic flows in aquatic food webs
Food-web modelling is a key tool to provide a global and comprehensive knowledge on community structure, biodiversity and ecosystem processes and functioning. In particular, it allows computing integrative and holistic indices describing food web characteristics, topology and functioning. However, one of the main sources of uncertainty in most food-web models is the estimation of diet matrices. In the present work, we propose an innovative approach that combines (a) a Bayesian mixing model using both isotopes and contaminants as chemical tracers with (b) classical mass-balance equations. This dual approach allows the simultaneous estimation of diet composition, isotopic enrichment, contaminant biomagnification, and contaminants and biomass flows in the whole food web. This original model named ESCROpath also provides food-web indices derived from ecological network analysis (ENA). As a case study, the approach was implemented in the Gironde estuarine food web (SW France) for which isotopes, contaminants and trophic data exist. Two sets of priors were constructed accounting for more or less uncertainty in trophic parameter estimates. Outputs were compared with previous published Ecopath results. A constrained calibration led to very similar outputs as Ecopath (which shows that the method is able to find the initial set of parameters if it is forced to do so), whereas a free calibration led to slight differences in trophic parameters and ENA indice estimations (which shows that the Ecopath solution was not fully optimal). Quite different diet matrices and estimations of flows distribution within the food web can thus be obtained. ESCROpath is an original flexible food-web modelling tool that, for the first time, makes it possible to go from a model mainly built on an ‘estimate’ of the parameters based on expert knowledge (which constitutes the main criticism formulated against Ecopath) to a statistical Bayesian framework for the estimation of the trophic parameters. It thus provides a very integrated framework for food-web modelling by estimating simultaneously trophic parameters, diet compositions and trophic enrichment/magnification factors. By doing this, it notably provides reliable and robust uncertainty estimations for output parameters.
(Methods in Ecology and Evolution. vol. 13, n° 2041-210X, pp. 894-907, 01/04/2022)
UR EABX, INRAE, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], IRSTEA, DECOD, IFREMER, INRAE, Institut Agro, Institut Agro, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Bioaccumulation of Per and Polyfluoroalkyl Substances in Antarctic Breeding South Polar Skuas (Catharacta maccormicki) and Their Prey
Per and polyfluoroalkyl substances (PFASs) are found in Antarctic wildlife, with high levels in the avian top predator south polar skua ( Catharacta maccormicki ). As increasing PFAS concentrations were found in the south polar skua during the breeding season in Antarctica, we hypothesised that available prey during the breeding period contributes significantly to the PFAS contamination in skuas. To test this, we compared PFAS in south polar skuas and their main prey from two breeding sites on opposite sides of the Antarctic continent: Antarctic petrel ( Thalassoica antarctica ) stomach content, eggs, chicks, and adults from Svarthamaren in Dronning Maud Land and Adélie penguin chicks ( Pygoscelis adeliae ) from Dumont d’Urville in Adélie Land. Of the 22 PFAS analysed, seven were present in the majority of samples, except petrel stomach content [only perfluoroundecanoate (PFUnA) present] and Adélie penguins (only four compounds present), with increasing concentrations from the prey to the skuas. The biomagnification factors (BMFs) were higher at Dumont d’Urville than Svarthamaren. When adjusted to reflect one trophic level difference, the BMFs at Svarthamaren remained the same, whereas the ones at Dumont d’Urville doubled. At both the colonies, the skua PFAS pattern was dominated by perfluorooctanesulfonic acid (PFOS), followed by PFUnA, but differed with the presence of branched PFOS and perfluorotetradecanoate (PFTeA) and lack of perfluorononanoate (PFNA) and perfluorodecanoate (PFDA) at Dumont d’Urville. At Svarthamaren, the pattern in the prey was comparable to the skuas, but with a higher relative contribution of PFTeA in prey. At Dumont d’Urville, the pattern in the prey differed from the skuas, with the domination of PFUnA and the general lack of PFOS in prey. Even though the PFAS levels are low in Antarctic year-round resident prey, the three lines of evidence (pattern, BMF difference, and BMF adjusted to one trophic level) suggest that the Antarctic petrel are the significant source of PFAS in the Svarthamaren skuas, whereas the skuas in Dumont d’Urville have other important sources to PFAS than Adélie penguin, either in the continent or external on the inter-breeding foraging grounds far from Antarctica.
(Frontiers in Marine Science. vol. 9, n° 2296-7745, 31/03/2022)
UiO, NILU, CEBC, ULR, CNRS, INRAE, LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IUF, M.E.N.E.S.R., NMBU
Les nutriments dans les écosystèmes côtiers : évolution à long terme, forçages du changement global et conséquence sur la biomasse et la diversité du phytoplancton
Du fait de leur position à l’interface entre les écosystèmes continentaux, les écosystèmes océaniques et l’atmosphère, les écosystèmes côtiers sont soumis à de nombreuses pressions et sont particulièrement sensibles aux perturbations. En effet, ils sont un lieu important pour de nombreux processus biogéochimiques et comptent parmi les zones les plus productives de la planète. Ainsi, étudier l’évolution des écosystèmes côtiers au travers des prismes des concentrations en nutriments et de la structure des communautés phytoplanctoniques devient intéressant et indispensable afin de comprendre l’impact du changement global sur ces écosystèmes. Les pressions qu’ils subissent sont en grande partie d’origine naturelle, mais, au cours du dernier siècle, ces dernières ont été modifiées en nombre, en intensité et en magnitude par les activités de l’homme. En effet, les pratiques agricoles et industrielles ont engendré une augmentation des apports nutritifs dans les écosystèmes côtiers. L’augmentation de la température, couplée aux perturbations des régimes des vents et des précipitations, a entrainé des modifications des échanges entre les écosystèmes côtiers et les compartiments voisins (continent, océan, sédiment, atmosphère). Afin de déterminer l’influence du changement global sur les écosystèmes côtiers, cette thèse se base sur des services d’observation français (SOMLIT, REPHY), au travers de 29 stations réparties dans 11 écosystèmes sur les 3 façades maritimes françaises. Des données d’apports continentaux et de la variation climatique locale et régionale ont été couplées aux mesures in-situ et considérées comme données forçantes. Les relations entre les forçages environnementaux et les écosystèmes côtiers ont été étudiées au travers d’un panel d’analyses statistiques univariées et multivariées.Il en ressort que les écosystèmes côtiers français présentent une grande diversité de caractéristiques (statut trophique, habitat, climat, apports continentaux…) et que cette diversité permet de différencier spatialement les écosystèmes. Cependant, leurs évolutions temporelles, étudiées au travers de 3 prismes (concentrations en nutriments, structures taxonomique et fonctionnelle des communautés phytoplanctoniques), ont permis de grouper certains écosystèmes entre eux, en fonction de leurs caractéristiques, selon l’approche considérée. Certains écosystèmes se sont démarqués en montrant des évolutions opposées au schéma général détecté (e.g. vers une diminution des concentrations en nutriments).Cela met en lumière le caractère dynamique et la complexité des écosystèmes côtiers, bien que les écosystèmes côtiers français soient situés dans une zone géographique limitée.
(31/03/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Himasthla spp. (Trematoda) in the edible cockle Cerastoderma edule: review, long-term monitoring and new molecular insights
Trematodes are the main macroparasites in coastal waters. The most abundant and widespread form of these parasites is metacercaria. Their impact on their host fitness is considered relatively low but metacercarial larvae of some species can have deleterious effects on individuals and/or populations. This review focused on the cockle Cerastoderma edule and four species of the genus Himasthla; a common host–parasite system in marine coastal environments. Our aims were (1) to review literature concerning Himasthla continua, Himasthla elongata, Himasthla interrupta and Himasthla quissetensis in cockles; (2) to provide molecular signatures of these parasites and (3) to analyse infection patterns using a 20-year monthly database of cockle monitoring from Banc d'Arguin (France). Due to identification uncertainties, the analysis of the database was restricted to H. interrupta and H. quissetensis, and it was revealed that these parasites infect cockles of the same size range. The intensity of parasites increased with cockle size/age. During the colder months, the mean parasite intensity of a cockle cohort decreased, while infection occurred in the warmest season. No inter-specific competition between trematode parasites was detected. Furthermore, even if the intensity of H. interrupta or H. quissetensis infection fluctuated in different years, this did not modify the trematode community structure in the cockles. The intensity of infection of both species was also positively correlated with trematode species richness and metacercarial abundance. This study highlighted the possible detrimental role of Himasthla spp. in cockle population dynamics. It also revealed the risks of misidentification, which should be resolved by further molecular approaches.
(Parasitology. vol. 149, n° 0031-1820, pp. 878-892, 30/03/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Toward the Sustainable Use of Groundwater Springs: A Case Study from Namibia
The water supply in drylands mainly relies on groundwater, making it a crucial resource. Springs in southern Africa are often underutilized, and are neither protected nor monitored. Thus, the aim of this study was to evaluate their quality in a sample area in northwestern Namibia and to propose solutions for the sustainable use of springs. In total, 35 springs and hot springs were evaluated in the study area located in the drier part of Namibia (Pmean = 150–400 mm/year), an area highly impacted by ongoing climate change with longer and more frequent drought seasons. The springs there are mostly uncaptured and the discharge is in the form of surface runoff, which is mainly lost to the atmosphere by evaporation. Most of the studied springs were perennial, despite a severe drought period. Local communities rely on the springs mainly for livestock and human consumption, as well as for irrigation. However, 71% of the springs do not have any protective measures. The temperature, pH, conductivity and alkalinity were tested in situ. In total, 20 samples were collected and analyzed for major ions (boron, fluoride, silica and strontium) and total dissolved solids (TDS). The physical and inorganic results mostly indicated good and excellent quality water for human consumption, while the hot springs tended to have poor water quality in terms of Namibian standards, indicating that the water was not fit for human consumption.
(Sustainability. vol. 14, n° 2071-1050, 28/03/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Influence of the bioturbating macrofauna on sediment biogeochemical dynamics and microphytobenthic activity in coastal ecosystems.
In coastal intertidal ecosystems, microphytobenthos (MPB) is one of the major primary producers, constituting an important source of carbon for benthic fauna. Environmental factors such as light, temperature, nutrient concentration in sediments, and grazing by benthic fauna are known to control MPB dynamics. In contrast, the influence of macrofaunal bioturbation, including sediment reworking (i.e., transport of sediment particles) and bioirrigation (i.e., transport of pore water and dissolved compounds), on MPB activity has been poorly studied. Thus, the aim of this study was to perform laboratory experiments to simultaneously quantify (1) the bioturbation activity of three dominant benthic intertidal macrofauna species (Hediste diversicolor, Scrobicularia plana and Cerastoderma edule), (2) oxygen and nutrients fluxes (ammonium, nitrate, nitrite, phosphate et silicate) at the water-sediment interface, and (3) biomass and photosynthetic activity of the MPB. Possible modulation of interactions by functional traits of bioturbators, sediment types, parasite infection, and density of organisms was also considered.Our results showed that the influence of macrofauna on MPB biomass and photosynthetic parameters mainly depends on the mode and intensity of bioturbation. Thus, the surface biodiffusor S. plana generates high sediment reworking due to an intense siphonal activity during feeding periods. Consequently, MPB biomass was reduced, despite a slight stimulation of nutrient fluxes. In contrast, the gallery biodiffusor H. diversicolor strongly increases nutrient availability through its intense bioirrigation activity, which would offset the negative effect of grazing pressure and surface sediment disturbance. Indeed, no net global significant effect on MPB dynamics was detected. The impact of the surface bioidiffusor C. edule on MPB biomass depends on its sediment environment. The sediment reworking generated by cockle, mainly related to its foraging and locomotion activities, is higher in cohesive than in non-cohesive sediments. Therefore, the impact on MPB biomass is negative in cohesive sediments, despite slight stimulation of nutrient fluxes. In contrast, no effect was detected in non-cohesive environments. Regarding other environmental factors, the macroparasite Himasthla elongata, infecting cockle at the metacercarial stage, does not alter the bioturbation activity and its impact on sediment biogeochemical dynamics, at least in young hosts. Furthermore, the relationship between MPB biomass and organism density is not always linear. Intraspecific competition can modify the feeding and bioturbation activities of individuals, with contrasting effects on MPB. Finally, this thesis highlights that the impacts of macrofaunal activity on MPB dynamics result from a tradeoff between stimulating and inhibiting factors, modulated by biotic and abiotic factors. These experiments show the importance of benthic macrofaunal bioturbation in the functioning of coastal and estuarine intertidal ecosystems.
(25/03/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Dynamique de la Mediterranean Outflow Water dans le Golfe de Cadix depuis le Pléistocène.
La sédimentation de la pente moyenne du Golfe de Cadix est fortement influencée par l’écoulement d’un courant de fond d’origine méditerranéenne : la Mediterranean Outflow Water (MOW). La compréhension de la relation entre l’écoulement de la MOW, l’Atlantic Meridional Overturning Circulation (AMOC) et les variations climatiques en Atlantique Nord représente un enjeu majeur et complexe. Ces travaux de thèse, en étudiant les caractéristiques sédimentaires des sédiments des drifts contouritiques du Golfe de Cadix, corps sédimentaires propices à l’étude de la variabilité des courants de fond, visent à comprendre la dynamique de la MOW depuis le Pléistocène inférieur. Cette étude s’appuie essentiellement sur des archives sédimentaires prélevées lors de l’Expédition Integrated Ocean Drilling Program 339 « Mediterranean Outflow » (2011-2012) et valorise également des carottes sédimentaires collectées durant la mission océanographique CADISAR (2001). Ce travail a permis d’identifier les sources des minéraux argileux composant les dépôts du système contouritique de Cadix (apports fluviatiles du Guadalquivir et poussières éoliennes nord-africaines) et mis en évidence les rôles de la circulation océanique de surface et l’écoulement de la MOW, dans la distribution des minéraux argileux dans le Golfe de Cadix. Les assemblages ostracodiques, la minéralogie des argiles ainsi que les mesures granulométriques, effectués à haute résolution sur des archives sédimentaires prélevées à différentes bathymétries, ont permis d’affiner le schéma de circulation de la MOW dans le système contouritique de Cadix pour le dernier cycle climatique. Des séries sédimentaires plus anciennes couvrant l’intervalle des Stades Isotopiques Marins (MIS) 12-11 ont montré que le modèle de fonctionnement général établi demeurait valable mais d’intensité moindre, pour l’analogue climatique le plus récent. Enfin les mesures granulométriques et des cortèges argileux réalisées à haute résolution sur une longue série sédimentaire du drift de Faro, mises en âges par une stratigraphie isotopique inédite, ont permis de déterminer trois phases de construction du drift de Faro ainsi que de reconstruire la dynamique de la MOW depuis le Pléistocène inférieur (1,2 Ma).
(18/03/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS