Fjords have been recently recognized as hot spots of organic carbon (Corg) sequestration in marine sediments. This study aims to identify regional and local drivers of variability of Corg burial in north Atlantic and Arctic fjords. We provide a comparative quantification of Corg, δ13C, photosynthetic pigments content, benthic biomass, consumption, Corg accumulation, and burial rates in sediments in six fjords (60–81°N). Higher sediment Corg content in southern Norway reflected longer phytoplankton growth season and higher productivity. Higher contributions of terrestrial Corg were noted in temperate/southern Norway (dense land vegetation and high precipitation) and Arctic/Svalbard (glacial erosion) than in subarctic/northern Norway locations. Benthic biomass and carbon consumption were best correlated to δ13C and photosynthetic pigments content indicating control by quality rather than quantity of available food. Benthic faunal consumption did not seem to affect the variability in Corg burial. Regional environmental factors (water temperature and latitude) combined with local factors (Corg, grain size, and pigment concentration) explained 94% of Corg burial variability. Based on the present study and literature data on Corg content, origin, and burial rates, the fjords were classified into four categories: temperate, subarctic, Arctic with glaciers, and Arctic without glaciers. The variability in marine productivity, terrestrial inflows, and carbon sequestration in fjords must be considered for global estimates of their role in blue carbon storage and for building scenarios of future changes in the course of climate warming. |
