The Potential Impact of Climate Change on Stream Water Quality

Joint research from two National Science Challenges, Our Land and Water and Deep South, implies that strategies to mitigate phosphorus losses from land to water should be strengthened to prevent potential water quality impairment under a changing climate.

Climate change will likely increase the growing season, temperatures and the ratio of nitrogen to phosphorus loss from land to water. This research investigated how these factors may influence phosphorus concentrations, and therefore algal concentrations in streams.

Differences in biotic and abiotic processes were evaluated for their effect on stream sediment phosphorus changes under different temperature and nitrogen enrichment regimes.

The rate and magnitude of phosphorus uptake by stream bed sediment was greater at the current maximum summer baseflow temperature (19°C) compared to the maximum summer baseflow temperate (26°C) expected under climate change conditions.

The addition of nitrogen, at a rate equivalent to lowland streams under dairying, stimulated phosphorus uptake by the microbial biomass at 19°C, but microbial phosphorus uptake was potentially inhibited at 26°C.

Because microbial biomass is a temporary store of phosphorus, these data suggest that more phosphorus may be available for periphyton growth with increasing temperatures during the growing season, especially under baseflow.

This work was the result of deliberations between the Our Land and Water National Science Challenge, the Deep South National Science Challenge and the USDA Agricultural Research Service. Estimates of likely temperature changes from the Deep South Challenge (and also pertinent to the US) were tested in bespoke facilities in the USA.

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For more on this research project, see:

• Temperature and nitrogen effects on phosphorus uptake by agricultural stream-bed sediments in Journal of Environmental Quality, March 2017