Extremely sheltered gravelly sandy mud, subject to variable salinity, on the mid and lower shore. The infaunal community consists of the ragworm Hediste diversicolor, Pygospio elegans, Streblospio shrubsolii, and Ampharete grubei, as well as oligochaetes and Corophium volutator. There are often low densities of Scrobicularia plana. Given the low sample numbers for this biotope, more records are needed to confirm the characterising species list. Situation: It is probable that there are broad transition areas between this biotope and the corresponding muddy sediment biotope, unit A2.3221. The boundaries may be very indistinct, with A2.4112 present in patches of gravelly mud on areas of mudflat, where the main biotope is A2.3221. This biotope has been found along edges of tidal channels in the upper Stour estuary, below its equivalent mud biotope.