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IntroductionWhile crucial to ensuring the production of accurate and high-quality data—and to avoid erroneous conclusions—data quality control (QC) in environmental monitoring datasets is still poorly documented. MethodsWith a focus on annual inter-laboratory comparison (ILC) exercises performed in the context of the French coastal monitoring SOMLIT network, we share here a pragmatic approach to QC, which allows the calculation of systematic and random errors, measurement uncertainty, and individual performance. After an overview of the different QC actions applied to fulfill requirements for quality and competence, we report equipment, accommodation, design of the ILC exercises, and statistical methodology specially adapted to small environmental networks (<20 laboratories) and multivariate datasets. Finally, the expanded uncertainty of measurement for 20 environmental variables routinely measured by SOMLIT from discrete sampling—including Essential Ocean Variables—is provided. Results, Discussion, ConclusionThe examination of the temporal variations (2001–2021) in the repeatability, reproducibility, and trueness of the SOMLIT network over time confirms the essential role of ILC exercises as a tool for the continuous improvement of data quality in environmental monitoring datasets.

Les données issues des comptages de zooplancton gélatineux effectués lors des campagnes halieutiques sont des données quantitatives mais non standardisées (i.e. non comparables d’une campagne à l’autre, ou d’un trait à l’autre). Cette note technique explore les questionnements méthodologiques permettant la standardisation et la comparaison de ces données et présente une proposition de méthode d’estimation de l’abondance du zooplancton gélatineux à partir de captures par chalutage. Ce travail fait suite aux réflexions antérieures menées dans le cadre de la DCSMM par Sandrine Vaz, Fabien Morandeau, Fabien Lombard et Jacques Sacchi concernant l’exploitation des données de zooplancton gélatineux acquises par chalutage (Aubert et al. 2018 ; Lheureux et al. 2022). Ces travaux ont été poursuivis dans le cadre du projet R&D GELATINE et les principales propositions et résultats sont discutés ici au regard des données existantes (types de chaluts, distance de chalutage et référentiel utilisé, zone filtrante du chalut).

Aim The criteria used to define the International Union for Conservation of Nature (IUCN) Red List categories are essentially based on demographic parameters at the species level, but they do not integrate species' traits or their roles in ecosystems. Consequently, current IUCN-based protection measures may not be sufficient to conserve ecosystem functioning and services. Some species may have a singular combination of traits associated with unique functions. Such functionally distinct species are increasingly recognized as a key facet of biodiversity since they are, by definition, functionally irreplaceable. The aim of this study is to investigate whether threatened species are also functionally rare and to identify which traits determine extinction risk. Location European continental shelf seas. Time period 1984–2020. Major taxa studied Marine fish. Methods Using newly compiled trait information of 425 marine fish species in European waters, and more than 30 years of scientific bottom trawl surveys, we estimated the functional distinctiveness, restrictedness and scarcity of each species and cross-referenced it with their IUCN conservation status. Results In European continental shelf seas, 38% of the species threatened with extinction (9 out of 24 species) were identified as the most functionally distinct. By mapping extinction risk in the multidimensional species trait space, we showed that species with the greatest risk of extinction are long-lived and of high trophic level. We also identified that the most functionally distinct species are sparsely distributed (4% of the total area on average) and have scarce abundances (<1% of the relative mean abundance of common species). Main Conclusions Because a substantial proportion of threatened species are functionally distinct and thus may play unique roles in ecosystem functioning, we stress that species traits—especially functional rarity—should become an indispensable step in the development of conservation manage

The effect of environmental change in structuring the phytoplankton communities of the coastal waters of the Eastern English Channel was investigated by applying a trait-based approach on two decades (1996-2019) of monitoring on diatoms and Phaeocystis. We show that phytoplankton species richness in an unbalanced nutrient supply context was influenced by wind-driven processes, ecological specialization for dissolved inorganic phosphorous, temporal niche differentiation, and a competition-defense and/or a growth-defense trade-off, a coexistence mechanism where weak competitors (i.e., slower growing) are better protected against predation. Under the influence of both environmental perturbations (e.g., wind-driven processes, freshwater influence, unbalanced nutrient levels) and biotic interactions (e.g., competition, predation, facilitation), phytoplankton species exhibited specific survival strategies such as investment on growth, adaptation and tolerance of species to environmental stresses, silicification and resource specialization. These strategies have led to more speciose communities, higher productivity, functional redundancy and stability in the last decade. Our results revealed that the unbalanced nutrient reduction facilitated Phaeocystis blooms and that anthropogenic climate warming and nitrate reduction may threaten the diatom communities of the eastern English Channel in a near future. Our results provide strong support for biogeographical historical and niche-based processes in structuring the phytoplankton community in this temperate region. The variety of species responses that we characterized in this region may help to better understand future changes in pelagic ecosystems, and can serve as a basis to consider functional approaches for future ecosystem management.

Decadal time series of chlorophyll-a concentrations sampled at high and low frequencies are explored to study climate-induced changes on the processes inducing interannual variations in the Initiation of the Phytoplankton Growing Period (IPGP) in early spring. In this study, we specifically detail the IPGP in two contrasting French coastal ecosystems: the Bay of Brest and the Bay of Vilaine. A large interannual variability in the IPGP is observed in both ecosystems in connection with variations of environmental drivers (solar radiation, sea temperature, wind direction and intensity, precipitation, river flow, sea level, currents and turbidity). We show that the IPGP is delayed by around 30 days in 2019 in comparison with 2010. The use of a one-dimensional vertical model coupling hydrodynamics, biogeochemistry and sediment dynamics shows that the IPGP is generally dependent on the interaction between several drivers. Interannual changes are therefore not associated with a unique driver (such as increasing sea surface temperature). Extreme events also impact the IPGP. In both bays, IPGP is sensitive to cold spells and flood events. The interannual variability of the IPGP is significant and strongly conditioned, at the local scale, by a combination of several environmental parameters, with a larger sensitivity to sea temperature and light conditions, linked to the turbidity of the system. While both bays are hydrodynamically contrasted, the processes that modulate IPGP are similar. Keywords Phytoplankton biomass, Long-term in situ observations, Coastal ecosystems, Extreme events, Climate change.