The goal of this project was to provide the first estimates of blue carbon stocks and carbon accumulation rates in the high and low marsh zones of salt marshes from the Pacific Coast of Canada, within the Clayoquot Sound UNESCO Biosphere Reserve and Pacific Rim National Park Reserve on the Pacific Coast of Canada. Sediment cores were collected using a simple percussion coring technique in which a 57-mm diameter, PVC vacuum tubing fitted with a plastic core catcher (AMS Inc.) was hammered into the ground until the depth of refusal. At the GBK location, a steel sledge corer (AMS Inc.) was used to extract four cores before mechanical problems required switching to the simpler percussion method. This datafile provides a summary of the estimated C stocks and carbon accumulation rates for the thirty-four sediment cores that were collected from seven salt marshes during summer (June-September) 2016. The sediment type at the base of each core was recorded. We also recorded the deepest sediment depth at which peat was found, referred to as the depth of the “Peat Base.” This depth was used to estimate the C stock for the marsh. Compaction was measured as length of core penetration divided by the length of core recovered. Using the compaction factor, we provide estimates of “uncorrected” (using original core depths) and “corrected” (applying compaction factor) values for the dry bulk density (g/cm3) and soil carbon density (g C/cm3). We provide estimates of C stocks (a) to the peat base, (b) for the whole core, and (c) to the depth of the 30-year horizon in the eight cores for which we have measured 210Pb systematics. We calculated the mass of all carbon down to the base of the peat layer to estimate the C-stock to peat base for each core, and this calculation did not require use of the compaction factor. The “corrected” values were provided to facilitate comparison with other studies (and for calculating the 20-cm C stock). ArcMap 10.3 tools were used with 50 x 50 cm resolution aerial orthophotos (taken in July 2014, Government of British Columbia) to estimate the total marsh area for each marsh.

CBE=Cannery Bay EastCBW = Cannery Bay WestCRF = Cypress River FlatsGBK = Grice Bay- Kootowis CreekKCS = Kennedy Cove SouthSWC = Shipwreck CoveTMF = Tofino Mud Flats