Gaping activity of eight O. edulis (oyster 1 to 8) deployed in a concrete basin in the Oosterschelde. The x-axis denotes time (days). The left y-axis and black solid line denotes the relative valve gape (0 indicates closed and 1 indicates maximally opened) and the right y-axis and red dotted line denotes the height of the tidal level in meters. The dotted blue line indicates the point at which the tidal level drops below the edge of the concrete basin (no connection to surrounding water). The grey polygons indicate the time at which the tidal level is above the edge of the concrete basin.