Intertidal Monitoring of Muddy Gravel in Pen Llyn a'r Sarnau Special Area of Conservation (SAC) 2007 dataset https://portal.medin.org.uk/portal/start.php?tpc=007_NRW_DS111183 The purpose of this data capture was to carry out a repeat survey of sites previously surveyed to further test and develop monitoring methodology and collect monitoring data. In fully marine conditions on the lower shore, sheltered muddy gravel habitats can be particularly species rich due to the complex nature of the substratum supporting a high diversity of infauna and epifauna. Analysis of survey records held on the Marine Nature Conservation Review (MNCR) database suggest that fully saline sheltered muddy gravel communities are scarce in their British distribution, with available descriptions lacking detail and comprehensive data. This has been attributed to the habitats being difficult to survey and monitor, due to the large quantities of coarse material which require sampling and subsequent analysis. Similarly, historical data on the distribution of muddy gravel beds appears limited. This data set includes results of sediment coring and sampling undertaken at one site in Porthmadog during intertidal monitoring of the muddy gravel in Pen Llyn a'r Sarnau Special Area of Conservation (SAC). 20090331