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Sources, Sinks, and Subsidies: Terrestrial Carbon Storage in Mid‐latitude Fjords
Author(s) -
Smeaton Craig,
Austin William E. N.
Publication year - 2017
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2017jg003952
Subject(s) - fjord , sediment , oceanography , environmental science , terrestrial ecosystem , geology , hydrology (agriculture) , ecosystem , geomorphology , ecology , geotechnical engineering , biology
Fjords are recognized as globally important sites for the burial and long‐term storage of carbon (C) within sediments. The proximity of fjords to the terrestrial environment in combination with their geomorphology and hydrography results in the fjordic sediments being subsidized with organic carbon (OC) from the terrestrial environment. It has been well documented that terrestrial OC (OC terr ) is an important component of coastal sediments, yet our understanding of the quantity of OC terr stored in these sediments remains poorly constrained. Utilizing Bayesian isotopic sediment fingerprinting techniques to the surface sediments of Loch Sunart, we estimate that 42.0 ± 10.1% of the OC is terrestrial in origin. Through combining these outputs with sedimentary OC stock estimates, we have calculated that the surface sediments (0–15 cm) hold 0.1 megaton (Mt) OC terr and estimate that the postglacial sediment held within the fjord contains 3.96 Mt OC terr . When these totals are compared to the quantity of OC stored in the adjacent terrestrial environment, it is clear that the fjord's catchment stores a greater amount of OC terr in the form of vegetation and soil. Though when normalized for area the results suggest that the marine sediments are a more effective long‐term store of OC terr than the adjacent terrestrial environment. This striking result highlights the importance of the terrestrial environment as a source of OC to the coastal ocean and that the OC terr subsidy to the marine sediments is a significant mechanism for the long‐term storage of OC in coastal marine sediments.