Abstract
Identifying the coordinated responses and the biotic and abiotic drivers of aquatic ecosystem dynamics across space and time is the key to understanding and predicting ecosystem trajectories under global change. Here, we applied the concept of ecosystem synchrony (that is, similarities in temporal fluctuations of ecosystem functions across space) to evaluate: (1) the coordinated dynamics of 16 French gravel pit lakes and (2) how geographic proximity, abiotic and biotic similarities explain their level of synchrony. We quantified both multi-year (two-year period) and seasonal (warm vs. cold seasons) levels of synchrony in dissolved oxygen saturation using high-frequency (10 min) measurements. We showed that the two-year ecosystem synchrony was driven by the environmental similarities in abiotic (for example, nutrient levels, hydromorphology) and biotic (for example, fish biomass) conditions between lakes yet the relative influence of these two processes varied seasonally. Indeed, ecosystem synchrony during warm seasons was primarily driven by abiotic environmental conditions, likely reflecting the stronger control of physical and chemical conditions on ecosystem functioning. Conversely, biotic similarity was more influential on ecosystem synchrony during cold seasons, suggesting a greater influence of biological structure under reduced ecosystem productivity. Geographic distance had a negligible effect, likely due to the relatively limited spatial extent of the lake network. These findings highlight the value of ecosystem synchrony as a spatiotemporal integrator of ecosystem dynamics and emphasize the need to account for both the temporal scale and local biotic and abiotic context dependencies when assessing the ecological trajectories of ecosystems.