Impacts of damming and climate change on the ecosystem structure of headwater streams: a case study from the Pyrenees

ABSTRACT

Climate change, damming, and metal pollution are among the main anthropogenic threats to headwater streams. We designed a case study to assess how these stressors impact the ecosystem structure of headwater streams by using the biofilm and macroinvertebrate communities of a Pyrenean stream. We observed a strong seasonal pattern in the stream that interacted with the analysed stressors by having synergistic, but also antagonistic, responses on the ecosystem structural parameters. Both damming and a decrease in precipitation reduced the water flow of the stream and increased its temperature, which promoted an increase in algal and macroinvertebrate biomass at the expense of the biodiversity of their communities, a situation expected to worsen in a climate change context. The decrease in precipitation also increased the concentration of metals and metalloids in the water column and in biofilms, but the water diversion from damming reduced their contributions downstream. The maintenance of an adequate ecological flow in dam-impounded streams is encouraged to overcome these impacts in the current climate change context. More field studies are needed to assess how multiple anthropogenic stressors interact and threaten the ecosystem integrity in a realistic and applied context.

KEYWORDS:

• biofilm community
• climate change
• conservation ecology
• damming
• ecotoxicology
• macroinvertebrates

Acknowledgements

We thank the University of Girona and the Blanes Centre for Advanced Studies (CEAB-CSIC) for their support and the Technical Research Services at the University of Girona for the metal content analyses. We thank the owners and manager where the stream is located, the Evarts family and Mike for supporting our research, and the Apatura Iris research team. ALS also thanks Dr. Laura Barral-Fraga for her help with the identification of the diatom samples and Dr. David Cunillera, Dr. Irene Tornero, and Mr. Carlos Cano-Barbacil for their support and help with the statistical analyses. Macroinvertebrate samplings and analysis were carried out in compliance with ethical guidelines set for animal experimentation. Meticulous efforts were made to assure the least suffering to animals and to reduce external sources of stress, pain, and discomfort, and by sampling only the necessary individuals.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the Government of Catalonia, through the Agència de Gestió d'Ajuts Universitaris i de Recerca through the main author’s doctoral scholarship (code 2020FI_B1 00098).