Regime shifts in a shallow lake over 12 years: Consequences for taxonomic and functional diversities, and ecosystem multifunctionality

Abstract

1. Under increasing nutrient loading, shallow lakes may shift from a state of clear water dominated by submerged macrophytes to a turbid state dominated by phytoplankton or a shaded state dominated by floating macrophytes. How such regime shifts mediate the relationship between taxonomic and functional diversities (FD) and lake multifunctionality is poorly understood.2. We employed a detailed database describing a shallow lake over a 12-year period during which the lake has displayed all the three states (clear, turbid and shaded) to investigate how species richness, FD of fish and zooplankton, ecosystem multifunctionality and five individual ecosystem functions (nitrogen and phosphorus concentrations, standing fish biomass, algae production and light availability) differ among states. We also evaluated how the relationship between biodiversity (species richness and FD) and multifunctionality is affected by regime shifts.3. We showed that species richness and the FD of fish and zooplankton were highest during the clear state. The clear state also maintained the highest values of multifunctionality as well as standing fish biomass production, algae biomass and light availability, whereas the turbid and shaded states had higher nutrient concentrations. Functional diversity was the best predictor of multifunctionality. The relationship between FD and multifunctionality was strongly positive

Alternance of alternative stable states influence the functional diversity of microcrustaceans in a shallow subtropical lake

“…Turbidity, combined with the depth of aquatic environments, has caused changes in the functional traits of microcrustaceans, mainly related to the feeding type, life span, reproduction mode and escape from predators (Braghin et al 2020). Higher values of functional diversity were observed in periods with clear water state with submerged macrophytes compared with periods with turbid water state and shaded state by floating macrophytes (Moi et al 2022). A low number of functional traits with persistence of a few species with a set of similar functional traits was observed for periods of turbid water state and shaded state by floating macrophytes (Moi et al 2022).…”

“…Higher values of functional diversity were observed in periods with clear water state with submerged macrophytes compared with periods with turbid water state and shaded state by floating macrophytes (Moi et al . 2022). A low number of functional traits with persistence of a few species with a set of similar functional traits was observed for periods of turbid water state and shaded state by floating macrophytes (Moi et al .…”

“…A low number of functional traits with persistence of a few species with a set of similar functional traits was observed for periods of turbid water state and shaded state by floating macrophytes (Moi et al . 2022). For periods with clear water status with submerged macrophytes, a dominance of traits, such as greater body size, filtering species and low predator escape capacity was observed (Moi et al .…”

“…For periods with clear water status with submerged macrophytes, a dominance of traits, such as greater body size, filtering species and low predator escape capacity was observed (Moi et al . 2022). Thus, we can highlight that the functional approach is an excellent predictor for observing the relationship of the aquatic environment and the community, and to understand the functional structuring of the microcrustacean community facing the variations of alternative stable states in a shallow lake over time.…”

Planktonic functional diversity changes in synchrony with lake ecosystem state

“…However, despite these suggestions and repeated claims that functional diversity changes following dramatic state changes (e.g. land use change - Edwards et al 2014; lake regime shifts - Moi et al 2021), there remains a need to confirm that diversity changes also occur prior to ecosystem state change, as required by indicator selection frameworks (Dale & Beyeler 2001). To address this need, we must explore lagged relationships between functional diversity and ecosystem state to identify whether the former provides sufficient warning for management purposes and, if so, over what time horizon.…”