HCO⁺ (4−3) velocity-channel map of a model with an embedded Jupiter-mass planet as it could be observed using ALMA configuration 14 (1.6 km baseline). The flux density in Jy/beam is color coded for each individual channel. The inclination of the disk amounts to 0° (face-on). Compared to the same model but simulated ¹²C¹⁶O (3−2) observation, the line flux is about 35% lower owing to the distinct lower abundance of HCO⁺. However, because of the low abundance the gap is clearly detectable, even at the central wavelength.