This dataset contains information on infaunal abundance and biomass from sediment grabs taken off the coast of the Ards Penninsula, Northern Ireland in 2014 & 2016. This survey was carried out to contribute to a larger project to assess the status and extent of Modiolus modiolus biogenic reefs in this area. The biogenic reefs were in an unfavourable condition even though this Annex 1 habitat was the reason for the designation of the Strangford Lough Special Area of Conservation (SAC). This survey was carried out on board the RV Corystes using a 0.1m2 day grab. The infaunal communities were identified and weighed, particle size analysis and carbon & nitrogen analysis were carried out on the samples. In total there were 36 samples taken (only 30 could be analysed for infauna). The most abundant species recorded was the tunicate Dendrodoa grossularia and the most frequently recorded species was the mollusc Leptochiton asellus.