The dataset details surface sediment colloidal carbohydrate concentrations across six intertidal sites in the winter and summer of 2013. Colloidal carbohydrate concentrations in surface sediments (top 2mm) provide a quantitative measure of the extracellular polymeric substances (EPS) secreted by organisms that form the microphytobenthos (MPB) community. Three of the sites were in Morecambe Bay, North West England and three of the sites were in Essex, South East England, each of these sites consisted of a saltmarsh area and adjacent mudflat area, twenty two sampling quadrats were placed on each area. Five replicate sediment samples were taken at each quadrat and were analysed using the Dubois Phenol-Sulphuric Assay which involves spectrophotometer analysis of absorptions to determine colloidal carbohydrate concentrations. Values for colloidal carbohydrate concentrations are expressed as glucose equivalents in micrograms per gram of sediment. This data was collected as part of Coastal Biodiversity and Ecosystem Service Sustainability (CBESS): NE/J015644/1. The project was funded with support from the Biodiversity and Ecosystem Service Sustainability (BESS) programme. BESS is a six-year programme (2011-2017) funded by the UK Natural Environment Research Council (NERC) and the Biotechnology and Biological Sciences Research Council (BBSRC) as part of the UK's Living with Environmental Change (LWEC) programme. Full details about this dataset can be found at https://doi.org/10.5285/6c027bf9-b344-4178-b8b3-d78cf39f017f