Experimental design. Water levels were dropped onto the surface of the sediment in some channels (A, left channel), while 4.5 cm of water was maintained in others (A, right channel). (B) Channels were naturally fed by the Aitzeguerria and Lapitxuri brooks. After 48 days of colonisation by macroinvertebrates 100 μm mesh nets were placed at the beginning and end of the channels to study the dynamics of the community in place. A drying event was simulated for 15 days (grey channels) and then fish grew for 21 days (hatched areas).