EESS talk on "Dissolved oxygen provides insights into regime shifts and headwater network behavior"

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Event details

Date and time 23.02.2021 12:1513:00  
Place and room
ZOOM
Online https://epfl.zoom.us/j/84677261593
Speaker Dr Jake Diamond, postdoctoral researcher, RiverLy research unit, EcoFlows Team, INRAe Lyon and University of Tours, FR
Category Conferences - Seminars
Abstract:
Aquatic ecosystem recovery from anthropogenic degradation can be hampered 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 despite strong recent evidence that such shifts can and do occur. Using three decades of measurements of key state variables such as turbidity, nutrient concentrations, Corbicula fluminea clam densities, and chlorophyll a, including hourly dissolved oxygen, we investigated a sudden shift from phytoplankton to macrophyte dominance in the middle Loire River (France), and its associated effects on the rivers metabolic regime. We show that despite large and synchronous shifts across all state variables, changes in gross primary production and ecosystem respiration were modest (25% and 14% declines, respectively) and that these shifts lagged the ecosystem state changes by a decade or more. 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 temporal 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. We also present an exploration of headwater network patterns of dissolved oxygen.

Short biography:
Jake was born in Florida, USA, spending his youth in the swamps, marshes, rivers, springs, and beaches of his homestate. He maintained his interest in aquatic ecosystems during his undergraduate and master’s studies at the University of Florida, after which he spent time working in industry and state government in Salt Lake City, Utah. He then completed a PhD in ecohydrology at Virginia Tech before arriving at his current position as a research associate at INRAE in Lyon, France.
 

Practical information

  • General public
  • Free
  • This event is internal

Organizer

  • EESS - IIE

Tags

macrophytes phytoplankton primary production reoligotrophication regime shift networks

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