Can stream warming trigger internal nutrient remobilisation from sediments?

Rising water temperatures and increasingly frequent low-flow conditions are expected to intensify under climate change, yet their combined effects on internal nutrient loading in streams remain poorly understood. During summer, higher temperatures can enhance biological activity and organic matter mineralisation at the sediment–water interface, while reduced discharge limits oxygen supply, potentially stimulating nutrient release from sediments.

In this study, we investigate the mechanisms and drivers of nutrient remobilisation from stream sediments using controlled laboratory experiments under different temperature and low-flow scenarios. We specifically assess how temperature effects interact with sediment characteristics to determine the magnitude of internal nutrient release.

Our results show that nutrient remobilisation responds significantly to temperature changes; however, the response is non-linear and strongly dependent on the initial trophic state of the stream and sediment biomass. These findings suggest that stream warming may substantially enhance internal nutrient loading in some systems but not in others. This context-dependent response highlights the need to account for sediment legacy effects when assessing climate change impacts on stream water quality and when designing management strategies under prolonged low-flow conditions.