Details are given of a preliminary study of salt marshes near Sullom Voe, Mainland, Shetland, using 50 X 50 cm quadrats placed systematically along transects. Computer-generated clusters are shown to match well against generally accepted syntaxa, whilst high-similarity clusters in certain alliances possess internal structure related to dominance and to effects of freshwater irrigation. The syntaxa provisionally identified are the Eleocharion uniglumis, Armerion maritimae, Puccinellion maritimae, and grazed cliff top grasslands showing affinity to the Puccinellio-Spergularion salinae. Computer clusters with Puccinellia maritima and much Fucus muscoides are associated with active pioneer grass growth and with slumping and erosion on wet marshes, whilst more species-rich clusters reflect a loss of vigour in Puccinellia maritima at higher elevations.
Drier stonier marshes also display depositional and erosional features, the former being associated with active Puccinellia maritima growth at lower levels on the marsh. It is suggested that most of these processes involve the recycling of local marsh sediment material.