Distribution of modern dinocysts and pollen in the western Mediterranean Sea (Algerian margin and Gulf of Lion)
The Mediterranean Sea is generally described as an oligotrophic area where primary productivity is limited to a few coastal environments with nutrient-enriched fluvial input. However, several studies have revealed that the hydrology of the western Mediterranean has major seasonal productive patterns linked either to significant riverine input or to seasonal upwelling cells. This study aims to: i) discuss organic microfossils (i.e. pollen and dinoflagellate cyst assemblages, as well as other non-pollen palynomorphs) from two different productive areas of the western Mediterranean Sea, and ii) examine the importance of the interconnections between marine and continental influences responsible for modern palynomorph distributions. Based on 25 samples from the Gulf of Lion (GoL) and Algerian Margin, this study key findings are: i) that GoL marine productivity is driven by the combination of discharge from the Rhône River and seasonal upwelling mechanisms, ii) that the strong productive pattern of the northern African coast is driven by water density front mixings and related upwelling. These two patterns are discussed in the light of major links that provide a better understanding of the signatures of marine and continental bio-indicators. Typical differences in vegetation across the north-south climate gradient in the western Mediterranean Basin are highlighted by the larger ratio of Euro-Siberian to Mediterranean pollen taxa in the northern sector. Synoptic maps also illustrate the complex interactions of environmental drivers determining the distributions of continental and marine palynomorphs in the western Mediterranean Sea.
(Marine Micropaleontology. vol. 175, n° 0377-8398, 01/08/2022)
LGO, UBS, IFREMER, UBO EPE, CNRS, HNHP, MNHN, UPVD, CNRS, UMR ISEM, Cirad, EPHE, PSL, CNRS, UM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, [Total Energies. Anciennement : Total, TotalFina, TotalFinaElf]
Effect and response traits in severe environments in the context of positive plant–plant interactions. A commentary on: ‘Interspecific interactions alter plant functional strategies in a revegetated shrub-dominated community in the Mu Us Desert’
Studies of plant functional traits have considerably increased our understanding of the mechanisms driving plant–plant interactions and community assembly. In benign environments with dominant negative interactions, competitive outcomes are driven mainly by the advantage associated with particular trait values, and trait dissimilarity between interacting species appears necessary for stabilizing niche differences and species coexistence (Kraft et al., 2015). In severe environments, with positive plant–plant interactions (i.e. facilitation) being the main force driving species coexistence, species are more prone to benefit from facilitation by nurse plants when they are functionally dissimilar from their nurses (Navarro-Cano et al., 2019). In the most severe environments, with intense abiotic filters, only highly stress-tolerant species with strong functional similarity remain in the communities, which often leads to a collapse of positive interactions (Liancourt et al., 2017). Thus, the degree of functional similarity is a critical driver of plant–plant interactions in severe environments.
(Annals of Botany. vol. 130, n° 0305-7364, pp. 149–159, 01/08/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Marine trematode parasites as indicators of environmental changes
Coastal ecosystems are threatened by growing pressures related to global change. The evaluation of an ecosystem’s biodiversity and status is by consequence of increasing importance to assess potentially undergone changes and predict their future trajectory for management and conservancy purposes. Biotic indicators sensitive to ecosystem changes are thus continuously sought for. Trematode parasite communities were examined as potential indicators of environmental changes, considering that the achievement of their complex life cycle is modulated by several factors. Indeed, the rule for trematode is that each species complete their cycle by a succession of three different host species and two free-living stages, thus depending on several biotic and abiotic factors. To this end, we examined the trematode community infecting the common cockle in Banc d’Arguin, Arcachon Bay, France. Monthly data extending over 16 years and sampled at a single station were compared to field book notes describing the changes of the closely surrounding landscape. In 2021, we also sampled cockles at 15 stations presenting different substrate features along the bank. Over time, seven out of nine changes of the trematode community structure presented concordances with changes in landscape. We hypothesize this was related to the environment heterogeneous substrate (i.e., temporal succession of oyster parks, bare sands and seagrass) with cascading effects on host populations. However, some changes could not solely be explained by changes in landscape. Our spatial study showed that the trematode communities exhibited intricate infection patterns with a complex interaction between substrate heterogeneity and larval dispersal ability of parasites. Thus, trematode communities might be potential indicators of subtle changes in the environment. However, it remains unclear which scale of environmental changes trematodes are actually sensitive to.
(Ecological Indicators. vol. 141, n° 1470-160X, pp. 109089, 01/08/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMS, UB, CNRS
Shoreline contour, water level elevation and volumetric dataset (1984-2020) for the Gallocanta Lake (NE Spain)
Gallocanta is the largest well-preserved saline lake in Western Europe, included in the Ramsar List. Associated with its shallow morphology, the lake undergoes strong variations in its water surface extent along time that condition the habitat distribution and the ecological functions. Data on the morphology of the lake and its hydrological variations along time may be of paramount ecological importance for the managers of this natural space. Even though its interest for research and management purposes, no accurate and robust dataset of this nature covering large periods of time is available. This dataset presents a multi-decadal mapping with a sub-weekly frequency (2-5 days) of the contour of the Gallocanta Lake (NE Iberian Peninsula) along the period 1984-2020 (1043 dates with information). The shoreline position appears continuously defined with subpixel accuracy from the freely-available images acquired by the satellites Sentinel-2 (sensor MSI) and Landsat 5 (TM), 7 (EMT+), and 8 (OLI) by applying the extraction system SHOREX. The satellite-derived shorelines allow the definition of the surface of the lake and are combined with a digital elevation model to assign elevation values to the points defining each shoreline. This allows deducing the mean elevation of the water level and the volumetric changes for those same dates. This data package constitutes a valuable source of information for carrying out robust analyses of the trends of the lake along decades, as well as its response to individual rainfall events.
(Data in Brief. vol. 43, n° 2352-3409, 01/08/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Geomorphological control of sandy beaches by a mixed-energy tidal inlet
Coastal areas adjacent to tidal inlets are highly valuable areas for marine ecosystems where a wide range of social and economic activities can be found. These areas can be differentiated from open coast due to their specific morphological behaviour caused by a complex nearshore bathymetry and interactions between wave and tidal forcing. The understanding of these interactions is usually limited by the lack of a systemic approach and the scarce availability of comprehensive datasets covering subtidal, intertidal and supratidal areas at large spatial and temporal scales. Here, the complementary use of different bathymetric and topographic datasets and the development of innovative methods using satellite imagery, offers the opportunity to develop a comprehensive understanding of the timescales and the key processes involved in the dynamics of tidal inlets and its control on the downdrift coast. The use of satellite-derived bathymetric maps, computed over the last two decades, showed two sequences of 8 and 9 years where large sandy shoals migrated along the tidal inlet and welded onto the downdrift coast. Although the study period covers one of the most energetic winter over the last decades, the most significant sediment volume changes (±300 m3/m) observed along the three kilometres of beach located south to the inlet were mostly attributed to the migration and welding of these sandy shoals, whereas the offshore wave forcing was of secondary importance. It was also demonstrated that these migrating and welding events had an impact on the pattern of the nearshore bathymetry and sandbars down to 10 km south to the inlet. Primary welding events near to the inlet are associated to the formation of kilometre-long and alongshore uniform nearshore sandbars that subsequently migrate further down the coast causing secondary welding events. The ability to understand and define the spatial and temporal boundaries at which beach behaviour is controlled by a local tidal inlet gives the opportunity to develop sediment compartment approach in order to make accurate predictions of future beach behaviour.
(Marine Geology. vol. 450, n° 0025-3227, 01/08/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Effects of Stochastic Wave Forcing on Equilibrium Shoreline Modelling Across the 21 st Century Including Sea-Level Rise
Coastal communities are currently facing the challenge of climate change and coastal retreat. While scientists are moving towards ensemble-modelling approaches to address uncertainties on shoreline evolution predictions, they rarely account for the stochastic nature of wave conditions across a variety of temporal scales (e.g., daily, weekly, seasonal, and interannual). In this contribution, we investigate the effects of the inherent variability of wave conditions on past and future multi-decadal shoreline evolution at the, cross-shore transport dominated, beach of Truc Vert (France). Using a climate-based wave emulator and variance decomposition method, we address the relative impacts of uncertain wave chronology, sea-level rise and model free parameters on modelled shoreline change, while accounting for possible correlations and interactions among the input variables. This work is done for two different wave-driven equilibrium models. The results show that the equilibrium shoreline models respond differently to the ensemble wave forcing, with strong implications on the long-term variability of modelled shoreline. We find that the modelled shoreline variance is primarily driven by the uncertain wave chronology until mid-21 st century, while the uncertainties on future sea-level rise become dominant after 2060 in all the simulated scenarios. We also found that interactions and correlations among the uncertain variables can affect the estimation of shoreline predictions uncertainties. Finally, we provide a perspective on the application of non-stationary wave-related model parameters as future research avenue for understanding uncertainties in modelled shoreline.
(Coastal Engineering. vol. 175, n° 0378-3839, pp. 104149, 01/08/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, UC / UniCan
Crossing the Boundaries: How Key Advancements in Understanding of Headland Sediment Bypassing Improves Definition of Littoral Cells
Headland sediment bypassing connects short-term physical forcing and long-term morphological response. The contributions from King et al., 2021 are a substantial step in understanding the complexities by combining field observations, process-based numerical modeling, and empirical generalization with the development of an improved parametrization of headland sediment bypassing. This study adds to the growing body of knowledge about littoral cell boundaries, or as proposed in this commentary, littoral cells that respond to varying wave energy and water levels that may influence the results from shoreline position models. Evolution of the shoreline in the context of climate change can be better understood by considering variability in littoral cell boundaries.
(Journal of Geophysical Research. Oceans. vol. 127, n° 2169-9275, 01/08/2022)
NOAA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impacts of chemical stress, season, and climate change on the flounder population of the highly anthropised Seine estuary (France)
The main objective of this study was to improve our knowledge on the responses of fish populations to multistress (diffuse pollution and warming waters) in estuaries. Adult flounders were caught in two estuaries in the Eastern English Channel: the heavily polluted Seine estuary vs the moderately contaminated Canche estuary. Fish samplings were conducted in January just before the reproduction period, and in July when gonads were at rest. The overall rise in coastal winter water temperatures detected over the Channel impairs the flounder's phenology of reproduction in the two estuaries, inducing a delay of maturation process and probably also spawning. The higher liver histopathology index in Seine vs Canche could be the consequence of the fish exposition to a complex cocktail of contaminants in a strongly industrialized estuary. Higher levels of neurotoxicity, gill lipid peroxidation, and liver EROD activity were observed in Seine vs Canche. Furthermore, a possible impairment in mitochondrial metabolism was suggested in the Seine flounder population. We confirmed in this study the potential role of two membrane lipids (sphingomyelin and phosphatidylserine) in the resistance towards oxidative stress in Seine and Canche. Finally, we suggest that the Seine flounder population (and possibly the connected Eastern English Channel flounder populations over the French Coast) could be seriously impacted in the future by multistress: higher winter temperatures and chemical contamination.
(Environmental Science and Pollution Research. vol. 29, n° 0944-1344, pp. 59751-59769, 01/08/2022)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, Cedre, LASIRE, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIEC, INSU - CNRS, UL, CNRS, GIP-Seine-Aval, LEHNA IAPHY, LEHNA, UCBL, ENTPE, CNRS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO
Early molecular responses of mangrove oysters to nanoplastics using a microfluidic device to mimic environmental exposure
This study assessed the effects of nanoplastics (NPs) using for the very first time microfluidic devices (chip) mimicking transition waters. Three kinds of NPs were tested: crushed NPs from polystyrene pellets (NP-PS), or from Guadeloupe beaches (NP-G); and latex PS (PSL-COOH). The eluted fractions from the microfluidic device showed a low aggregation of NPs. They remained stable over time in the exposure media, with a stabilization of NPs of small sizes (< 500 nm). These chips were thus used for the toxicological assessment of NPs on swamp oysters, Isognomon alatus. Oysters were exposed for 7 days to the chip elution fraction of either NP-G, NP-PS or PSL-COOH (0.34 to 333 µg.L-1). Gene transcription analyses showed that the tested NPs triggered responses on genes involved in endocytosis, mitochondrial metabolism disruption, oxidative stress, DNA repair, and detoxification. Highest responses were observed after NP-G exposure at low concentrations (1 µg.L-1), as they are originated from the natural environment and accumulated contaminants, enhancing toxicological effects. As salinity influences aggregation and then the bioavailability of NPs, our results demonstrated the importance of using microfluidic devices for ecotoxicological studies on swamp or estuarine species.
(Journal of Hazardous Materials. vol. 436, n° 0304-3894, pp. 129283, 01/08/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GR, UR, INSU - CNRS, CNRS, IPR, UR, CNRS, ULaval
The Impacts of Precipitation on Fluorescent Dissolved Organic Matter (FDOM) in an Urban River System
Precipitation is considered a key factor influencing the fluorescent dissolved organic matter (FDOM) of urban rivers. However, the multiple effects of precipitation on FDOM in urban rivers and the long-term impacts of precipitation on the spatial patterns of FDOM are seldom known. Spatiotemporal variations of FDOM at 36 sites from the urban rivers of Jinan City during dry and wet seasons were investigated in this study. Four components were identified using an excitation–emission matrix and parallel factor analysis. Overall, the total fluorescence intensities in dry and wet seasons ranged from 6.59 to 35.7 quinine sulfate units (QSU) and 3.42 to 69.3 QSU, respectively. Significant variations were found for different components that C2 and C3 declined but C4 increased in the wet season (p < 0.05). The temporal variations for different components could be explained by the different combined effects of precipitation dilution and flushing. Three different reference FDOM sources, including background water, spring water, and wastewater treatment plant (WWTP) outlets, were illustrated using principal coordinate analysis (PCoA). The places of FDOM in most sites were more closed to the PCoA location of WWTP outlets in the dry season while central shifted in the wet season. The changes of FDOM sources in the wet season could be explained by the mixed effect of precipitation. In conclusion, this study provided new insights into the multiple impacts of precipitation on FDOM in urban river systems, and also data support for precise pollution discharge and water resource management.
(Water. vol. 14, n° 2073-4441, pp. 2323, 27/07/2022)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS