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Sheffield Floods

Sheffield Floods. A first look at aquatic invertebrate data collected before and after the June 2007 floods. Anna Ritchie and Lina Ilia. Setting. In June of 2007 more rain fell in two days than would usually fall within two months. Research questions.

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Sheffield Floods

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  1. Sheffield Floods A first look at aquatic invertebrate data collected before and after the June 2007 floods Anna Ritchie and Lina Ilia

  2. Setting • In June of 2007 more rain fell in two days than would usually fall within two months.

  3. Research questions • How are stream invertebrates impacted by flooding? • Impact on abundance and diversity? • Are both benthic and hyporheic communities affected in similar ways?

  4. Stream invertebrate communities • Benthic macroinvertebrates: • Live on the upper layer of riverbed substrates • Commonly used for biological assessment

  5. Hyporheic invertebrates: • Live beneath and adjacent to the riverbed • Both surface and groundwater influences • Comparatively little is known and understood about their ecology

  6. Barnsley Rotherham Sheffield Chesterfield Sampling in the Don Catchment • 20 sites on 12 rivers were sampled (hyporheic and benthic) at the end of may • Sites were re-sampled at the beginning of July, after the June floods • Sampling included some sites directly downstream of reservoirs

  7. Benthic vs Hyporheic hypotheses • Benthic abundance and diversity were expected to decrease • Hyporheic abundance and diversity were expected to increase

  8. Are there differences between pre- and post-flood samples? • Does abundance change? • Does diversity change? • Are there different taxa present before and after the floods? • Do individual taxa respond differently? • Do dams have an influence on the flood effect?

  9. Pre- and Post-Flood invertebrate abundance hyporheic benthic Paired t-test, p=0.59 N=20 Paired t-test,p<0.001 N=11

  10. Change in diversity hyporheic benthic p=0.41 N=20 p<0.001 N=11

  11. Are the same taxa present before and after the floods? • Benthic • Taxa present only after floods • Helodidae*, Corixidae* • Taxa present only before floods • Ceratopogonidae, Empididae • Hyporheic: • Taxa present only after floods: • Bosminidae, Sididae, Calanoida, • Taxa present only before floods: • none

  12. Do different taxa respond differently to the flood event? * * * * * * *

  13. Barnsley Rotherham Sheffield Chesterfield What about the dams?

  14. no dam with dam no dam with dam p=0.052 N=14 p=0.047 N=6 p<0.001 N=6 p=0.001 N=5 Change in mean invertebrate abundance between sites with and without dams

  15. Benthic vs Hyporheic hypotheses • Benthic abundance and diversity were expected to decrease • Supported by the results • Hyporheic abundance and diversity were expected to increase • Not supported by the results

  16. Conclusions • The two communities show different patterns before and after floods as well as between sites with and without dams However these patterns may be a result of various other factors (such as insect emergence or water chemistry)

  17. Next steps. . . • More thorough description of hyporheic invertebrate community • Investigate the importance of other measured variables (ex: substrate, discharge, water chemistry) • Resample in 2008 to look for seasonal effects, compare trends between years, and investigate the recovery of the communities

  18. Acknowledgements Marie Curie Early Stage Research Training Fellowship, Environment Agency, University of Sheffield Catchment Science Centre, Lorraine Maltby and Phil Warren, Everyone who helped out in the field during our mad dash to catch the immediate flood effects, and everyone who listened and offered advice…

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