The dataset contains stable isotope concentration (d13C and d15N) and community abundance data for a range of aquatic macroinvertebrate taxa measured during a mesocosm drought experiment. The aquatic macroinvertebrates were sampled from four mesocosm system blocks at the Llyn Brianne Experimental Observatory. There were three experimental treatments included within each block (100% [control], 50%, and 10% of the baseflow discharge). Samples were collected before the treatments, and after 30 days of exposure to the treatments. Taxa were identified down to family level for abundance measurements. The work was supported by the Natural Environment Research Council (NE/X010597/1), as part of a study to understand ecosystem responses to environmental change through quantifying ecological interactions in freshwater systems. Full details about this dataset can be found at https://doi.org/10.5285/a62a2f1c-2ed4-4ec9-b22c-c3b340a63ca5
