Description: The vast majority of freshly produced oceanic dissolved organic carbon (DOC) is derived from marine phytoplankton, then rapidly recycled by heterotrophic microbes. A small fraction of this DOC survives long enough to be routed to the interior ocean, which houses the largest and oldest DOC reservoir. DOC reactivity depends upon its intrinsic chemical composition and extrinsic environmental conditions. Therefore, recalcitrance is an emergent property of DOC that is analytically difficult to constrain. New isotopic techniques that track the flow of carbon through individual organic molecules show promise in unveiling specific biosynthetic or degradation pathways that control the metabolic turnover of DOC and its accumulation in the deep ocean. However, a multivariate approach is required to constrain current carbon fluxes so that we may better predict how the cycling of oceanic DOC will be altered with continued climate change. Ocean warming, acidification, and oxygen depletion may upset the balance between the primary production and heterotrophic reworking of DOC, thus modifying the amount and/or composition of recalcitrant DOC. Climate change and anthropogenic activities may enhance mobilization of terrestrial DOC and/or stimulate DOC production in coastal waters, but it is unclear how this would affect the flux of DOC to the open ocean. Here, we assess current knowledge on the oceanic DOC cycle and identify research gaps that must be addressed to successfully implement its use in global scale carbon models.

Description: This dataset includes organic carbon measurements on sediment samples collected in Bute Inlet (British Columbia, Canada) in October 2016 (cruise number PGC2016007) and October 2017 (cruise number PGC2017005) aboard the research vessel CCGS Vector. The cruise PGC2016007 took place between 7 October and 17 October 2016 and was led by Gwyn Lintern. The cruise PGC2017005 took place between 19 and 29 October and was led by Cooper Stacey. River samples were taken in the Homathko and Southgate rivers using Niskin bottles in the water column and a grab sampler in the river beds and the river deltas

Description: This dataset includes organic carbon measurements on sediment samples collected in Bute Inlet (British Columbia, Canada) in October 2016 (cruise number PGC2016007) and October 2017 (cruise number PGC2017005) aboard the research vessel CCGS Vector. The cruise PGC2016007 took place between 7 October and 17 October 2016 and was led by Gwyn Lintern. The cruise PGC2017005 took place between 19 and 29 October and was led by Cooper Stacey. Marine sediment samples were collected in Bute Inlet using a box corer for the sandy samples in the submarine channel and a piston corer for the muddy samples in the overbanks and distal basin.

Description: The data was obtained by performing ramped pyrolysis and oxidation with 14C analysis of the emitted CO2 gases using the sedimentary residue of incubated permafrost soil (Yedoma) in seawater. The related data sets of the incubation experiment and experiment description can be found at doi:10.1594/PANGAEA.956711 and bacterial data at https://github.com/matthiaswietz/yedoma-bacteria. The ramped pyrolysis and oxidation setup is described in Hemingway et al. (2017a) and thermogram data conversion in E,p space is described in Hemingway et al. (2017b). Radiocarbon analysis was performed following Mollenhauer et al. (2021).

Description: About 34% of global coast lines are underlain by permafrost. Rising temperatures cause an acceleration in erosion rates of up to 10s of meters annually, exporting increasing amounts of carbon and nutrients to the coastal ocean. The degradation of ancient organic carbon (OC) from permafrost is an important potential feedback mechanism in a warming climate. However, little is known about permafrost OC degradation after entering the ocean and its long term-fate after redeposition on the sea floor. Some recent studies have revealed CO2 release to occur when ancient permafrost materials are incubated with sea water. However, despite its importance for carbon feedback mechanisms, no study has directly assessed whether this CO2 release is indeed derived from respiration of ancient permafrost OC. We used a multi-disciplinary approach incubating Yedoma permafrost from the Lena Delta in natural coastal seawater from the south-eastern Kara Sea. By combining biogeochemical analyses, DNA-sequencing, ramped oxidation, pyrolysis and stable and radiocarbon isotope analysis we were able to: 1) quantify CO2 emissions from permafrost utilization; 2) for the first time demonstrate the amount of ancient OC contributing to CO2 emissions; 3) link the processes to specific microbial communities; and 4) characterize and assess lability of permafrost OC after redeposition on the sea floor. Our data clearly indicate high bioavailability of permafrost OC and rapid utilization after thawed material has entered the water column, while observing only minor changes in permafrost OC composition over time. Microbial communities are distinctly different in suspended Yedoma particles and water. Overall, our results suggest that under anthropogenic Arctic warming, enhanced coastal erosion will result in increased greenhouse gas emissions, as formerly freeze-locked ancient permafrost OC is remineralized by microbial communities when released to the coastal ocean.