Aquatic ecologists face challenges in identifying the general rules of the functioning of ecosystems. A common framework, including freshwater, marine, benthic, and pelagic ecologists, is needed to bridge communication gaps and foster knowledge sharing. This framework should transcend local specificities and taxonomy in order to provide a common ground and shareable tools to address common scientific challenges. Here, we advocate the use of functional trait‐based approaches (FTBAs) for aquatic ecologists and propose concrete paths to go forward. Firstly, we propose to unify existing definitions in FTBAs to adopt a common language. Secondly, we list the numerous databases referencing functional traits for aquatic organisms. Thirdly, we present a synthesis on traditional as well as recent promising methods for the study of aquatic functional traits, including imaging and genomics. Finally, we conclude with a highlight on scientific challenges and promising venues for which FTBAs should foster opportunities for future research. By offering practical tools, our framework provides a clear path forward to the adoption of trait‐based approaches in aquatic ecology.

Dormancy (diapause) is a key life-history strategy of pelagic copepods that allows them to thrive in highly seasonal environments. Successful dormancy of copepodid stages requires the ability to store energy efficiently (for example as lipids) and to slow down the rate of mobilization of this capital during the dormant period. The physiology of lipids in copepods has been extensively reviewed; however, data about the energetics of dormancy are currently scattered throughout the literature. Thus, we conducted a meta-analysis comparing the metabolism of active and dormant copepods in 15 species that undergo dormancy as copepodids. Linear mixed-effects models showed that the metabolic rate of dormant copepods is about one-fourth of the values for actively growing copepods, a level that remains consistent across a large range of body size or environmental conditions. Based on these metabolic rates, we used a numerical modelling approach to predict dormancy duration as a function of body mass and ambient temperature, and to explain the observed range of body masses at the initiation of dormancy. Our numerical approach also provides explanations for inter-and intra-specific variability in life-history strategies, such as

Imaging techniques are increasingly used in ecology studies, producing vast quantities of data. Inferring functional traits from individual images can provide original insights on ecosystem processes. Morphological traits are, as other functional traits, individual characteristics influencing an organism's fitness. We measured them from in situ image data to study an Arctic zooplankton community during sea ice break-up. Morphological descriptors (e.g., area, lightness, complexity) were automatically measured on 28,000 individual copepod images from a high-resolution underwater camera deployed at more than 150 sampling sites across the ice-edge. A statisticallydefined morphological space allowed synthesizing morphological information into interpretable and continuous traits (size, opacity, and appendages visibility). This novel approach provides theoretical and methodological advantages because it gives access to both inter-and intra-specific variability by automatically analyzing a large dataset of individual images. The spatial distribution of morphological traits revealed that large copepods are associated with ice-covered waters, while open waters host smaller individuals. In those ice-free waters, copepods also seem to feed more actively, as suggested by the increased visibility of their appendages. These traits distributions are likely explained by bottom-up control: high phytoplankton concentrations in the well-lit open waters encourages individuals to actively feed and stimulates the development of small copepod stages. Furthermore, copepods located at the ice edge were opaquer, presumably because of full guts or an increase in red pigmentation. Our morphological trait-based approach revealed ecological patterns that would have been inaccessible otherwise, including color and posture variations of copepods associated with ice-edge environments in Arctic ecosystems. Functional traits are any features-morphological, physiological, etc-measurable at the individual-level and affecting the fitness of the organism (Violle et al. 2007). They can be classified according to the ecological function that they influence, such as feeding, growth, reproduction, and survival (Litchman et al. 2013). Trait-based approaches appeared in plant ecology in the 70s (Grime 1974) and stated being used by aquatic ecologists in the early 2000s (Willby et al. 2000; Usseglio-Polatera et al. 2000; Benedetti et al. 2016; Martini et al. (in press)). Trait-based analyses are relevant in community ecology because an individual's set of traits given environment determines its success (Violle et al. 2007). Ecological interactions (predation, mutualism, etc.) happen between individuals, not between taxonomic groups. Therefore, using trait composition can simplify the analysis of ecosystem complexity by focusing on a few characteristics transcending taxonomic distinctions and impacting ecological strategies (Litchman et al. 2013). By studying the composition and distribution of individual traits in an ecosystem, its structure and dominant proc...

No abstract

No abstract

No abstract

Aim One of the primary characteristics that determines the structure and function of marine food webs is the utilization and prominence of energy‐rich lipids. The biogeographical pattern of lipids throughout the ocean delineates the marine “lipidscape,” which supports lipid‐rich fish, mammal, and seabird communities. While the importance of lipids is well appreciated, there are no synoptic measurements or biogeographical estimates of the marine lipidscape. Productive lipid‐rich food webs in the pelagic ocean depend on the critical diapause stage of large pelagic copepods, which integrate lipid production from phytoplankton, concentrating it in space and time, and making it available to upper trophic levels as particularly energy‐rich wax esters. As an important first step towards mapping the marine lipidscape, we compared four different modelling approaches of copepodid diapause, each representing different underlying hypotheses, and evaluated them against global datasets. Location Global Ocean. Taxon Copepoda. Methods Through a series of global model runs and data comparisons, we demonstrated the potential for regional studies to be extended to estimate global biogeographical patterns of diapause. We compared four modelling approaches each designed from a different perspective: life history, physiology, trait‐based community ecology, and empirical relationships. We compared the resulting biogeographical patterns and evaluated the model results against global measurements of copepodid diapause. Results Models were able to resolve more than just the latitudinal pattern of diapause (i.e. increased diapause prevalence near the poles), but to also pick up a diversity of regions where diapause occurs, such as coastal upwelling zones and seasonal seas. The life history model provided the best match to global observations. The predicted global biogeographical patterns, combined with carbon flux estimates, suggested a lower bound of 0.031–0.25 Pg C yr−1 of downward flux associated with copepodid diapause. Main conclusions Results indicated a promising path forward for representing a detailed biogeography of the marine lipidscape and its associated carbon flux in global ecosystem and climate models. While complex models may offer advantages in terms of reproducing details of community structure, simpler theoretically based models appeared to best reproduce broad‐scale biogeographical patterns and showed the best correlation with observed biogeographical patterns.

Permafrost thawing and erosion results in the enrichment of northern lakes by soil organic matter. These allochthonous inputs favour bacterial decomposition and may cause the draw-down of dissolved oxygen to anoxic conditions that promote methanogenesis. Our objective in the present study was to determine the seasonal variations in dissolved oxygen in a set of permafrost peatland lakes in subarctic Quebec, Canada, and to relate these changes to metabolic rates, ice cover, and mixing. The lakes had high dissolved organic carbon concentrations, and their surface waters in summer had greenhouse gas concentrations that were up to one (CO 2 ) to three (CH 4 ) orders of magnitude above air-equilibrium values, indicating their strongly heterotrophic character. Consistent with these observations, the peatland lakes had elevated rates of bacterial production and oxygen consumption. Continuous measurements of oxygen by in situ sensors and of ice cover by automated field cameras showed that the lakes became fully anoxic shortly after freeze-up. The waters were partially reoxygenated by mixing events in spring and fall, but in one lake, the bottom waters remained anoxic throughout the year. These observations provide a foundation for subsequent biogeochemical and modelling studies of peatland thaw lakes as an abundant class of Arctic freshwater ecosystems.Key words: oxygen, permafrost, respiration, thaw lakes, thermokarst.Résumé : Le dégel et l'érosion du pergélisol entraînent l'enrichissement des lacs du Nord en raison de l'apport de matière organique de sol. Ces apports allochtones favorisent la décom-position bactérienne et peuvent causer la diminution d'oxygène dissous jusqu'à des conditions anoxiques qui aident la méthanogénèse. Notre objectif en entreprenant cette étude était de déterminer les variations saisonnières d'oxygène dissous pour un ensemble de lacs de tourbière de pergélisol dans la région subarctique du Québec, Canada, et d'établir un rapport entre ces changements et les taux métaboliques, la couverture de glace et le mélange. Les lacs avaient des concentrations élevées en carbone organique dissous et en été leurs eaux de surface avaient des concentrations en gaz à effet de serre qui étaient jusqu'à un (CO 2 ) et à trois (CH 4 ) ordres de grandeur au-dessus des valeurs d'équilibre d'air, indiquant leur caractère fortement hétérotrophe. Conformément à ces observations, les lacs de tourbière avaient des taux élevés de production bactérienne et de consommation d'oxygène. Des mesures prises en continue d'oxygène au moyen de capteurs in situ et de couverture de glace au moyen de caméras automatisées de terrain ont indiqué que les lacs devenaient entièrement anoxiques peu de temps après le gel. Les eaux ont été partiellement ré-oxygénées au printemps et à l'automne en raison de phénomènes de mélange, mais dans un des lacs, les