HCO column densities at the M8 clumps. The circle markers correspond to the positions of the individual clumps, with the grey-scale image showing the JCMT SCUBA 870 µm dust continuum flux (see Fig. 2). The circle size corresponds to the beam size of the on-off observations with APEX and the IRAM 30m telescope. Two-coloured circles visualise distinct velocity components observed in the same beam.