With over 1,100 ponds, la Dombes (Ain, France) is the largest inland fish-producing region of France. Traditional fisheries-management approaches have been established over the past 500 years. Yet, climate change and intensified land-use are now threatening water quality, biodiversity as well as fisheries yield. In 2022 we studied 22 ponds for invertebrate biodiversity, greenhouse gas dynamics and microplastics. While we found no differences between the most common management practices (fertilize+feed+lime vs. fertilize+feed), unmanaged reference ponds showed contrasting patterns. Invertebrate richness and diversity were higher in unmanaged vs. managed ponds, but so were CO₂ emissions. For CH₄, emissions were elevated across all ponds. Initially, it was surprising that unmanaged ponds had the highest carbon emissions. Yet, the quinquennial draining of managed ponds combined with farming may prevent the accumulation of organic material. Microplastic concentrations in the water column were some of the largest observed in inland waters, with highly dynamic temporal and spatial patterns. Long-term-Ecological-Research will be vital to quantify the importance of hydrology, management and land use for the functioning and controls of these systems. Ultimately, this work will support the co-development of best-management practices to increase ecosystem services while maintaining fish yield.

Primary Presenter: Björn Wissel, Université Claude Bernard Lyon 1 (bjoern.wissel@univ-lyon1.fr)

Authors:

Zoraida Quiñones-Rivera, Université Claude Bernard - Lyon 1   (zoraida.quinones@univ-lyon1.fr)

Emma Mari, Université Claude Bernard - Lyon 1   (emma.mari@univ-lyon1.fr)

Paul Vouhé, Université Claude Bernard - Lyon 1   (paul.vouhe@univ-lyon1.fr)

Felix Vallier, Université Claude Bernard - Lyon 1   (felix.vallier@univ-lyon1.fr)

Manon Vallier, Université Claude Bernard - Lyon 1   (manon.vallier@univ-lyon1.fr)

Mohammad Wazne, Université Claude Bernard - Lyon 1   (mohammad.wazne@univ-lyon1.fr)

Florian Mermillod-Blondin, Université Claude Bernard - Lyon 1   (florian.mermillod-blondin@univ-lyon1.fr)

Laurent Simon, Université Claude Bernard - Lyon 1   (laurent.simon@univ-lyon1.fr)

Stefan Krause, University of Birmingham  (S.Krause@bham.ac.uk)

Fanny Colas, Université Claude Bernard - Lyon 1   (fanny.colas@univ-lyon1.fr)