Sediment fluxes and carbon budgets in Loch Creran, western Scotland

Sea lochs are regions where riverine and marine organic carbon (OC) undergoes decomposition, deposition or transportation to shelf slopes and the deep sea. According to the OC budget presented here, discharge from River Creran (1.44×106 kg a−1) and phytoplankton material (0.89×106 kg a−1) make up a significant input of OC to Loch Creran while 0.67×106 kg a−1 OC is from other sources. A total of 1.28×106 kg a−1 OC is deposited in the loch and 1.14×106 kg a−1 OC is oxidized in the water column. Discharge to the Lynn of Lorn consists of 0.58×106 kg a−1 OC. Hence Loch Creran is a sink for OC where 42.7% of the total OC input is buried and 38% and 1.7% decomposed in the water column and subsurface sediments, respectively. River Creran contributes 63% labile and 37% refractory organic matter to the loch. More than 95% of each of the total OC, lignin and organic matter deposited onto the surface sediments is buried in the subsurface sediments. Seventy-five percent of the total organic matter decomposed in the water column is labile. Output to Lynn of Lorn consists of 54.6% refractory organic matter.