The effect of increasing fine sediment load and drying duration on the re‐emergence of <i>Gammarus pulex</i> (Amphipoda: Gammaridae) from the subsurface following flow resumption

Environmental change and growing anthropogenic pressure on water resources is increasing the duration intensity of drying events in streams many geographical locations. Favourable sediment characteristics (e.g. high porosity low fine load within substrate matrix) may facilitate benthic macroinvertebrate use subsurface sediments response to drying. However, influence sedimentary subsequent recovery macroinvertebrates from initial vertical migration into, survival during unfavourable conditions within, re-emergence have not been directly observed. Transparent mesocosm tanks were used observe movement Gammarus pulex dry period (1, 7, or 21 days) (0.5–1 mm particle diameter for light heavy treatment) following rehydration resumption flowing conditions. Increasing volumes addition limited ability G. access re-emerge rehydration. The longest (21 reduced flow resumption. negatively affects taxa using as a refuge. Increased deposition has potential reduce both sub-surface once surface resumes. As rivers are beginning out, showing prolonged due global warming, it increasingly important that river management reduces input into increase riverbeds refuge by fauna.