2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

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5/27/2021 | 2:00 PM - 3:30 PM | METABOLIC REGIME SHIFTS AND ECOSYSTEM STATE ARE DECOUPLED IN A LARGE RIVER | Virtual Platform

METABOLIC REGIME SHIFTS AND ECOSYSTEM STATE ARE DECOUPLED IN A LARGE RIVER

Aquatic ecosystem recovery from anthropogenic degradation are often by internal feedbacks that stabilize undesirable states. The challenges of managing and predicting alternative states in lakes are well known, but state shifts in rivers and their attendant effects on ecosystem function remain understudied. Using three decades of measurements of key state variables such as turbidity, nutrient concentrations, Corbicula fluminea densities, chlorophyll a, and hourly dissolved oxygen, we investigated a sudden shift from phytoplankton to macrophyte dominance in the Loire River, France, and its associated effects on metabolic regime. We show that despite large, synchronous shifts across all state variables, changes in gross primary production (-25%) and ecosystem respiration (-14%) were modest, and lagged the ecosystem state changes by a decade. The shift to a macrophyte-dominated state reduced the sensitivity of primary production to abiotic drivers, altered element cycling efficiency, flipped the net carbon balance from positive to negative, and, crucially, weakened the temporal coupling between production and respiration. This weakened coupling, detected using Granger causality, increased the autocorrelation of net ecosystem production, yielding a robust early warning indicator of both state- and metabolic-shifts that may provide valuable guidance for river restoration.

Ecosystem functioning
Nutrient cycling
Organic matter

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Presenters/Authors

Jacob Diamond (), INRAE, diamondjacob@gmail.com;