Dissolved organic carbon (DOC) is the largest organic carbon pool in the ocean. While in the open waters this pool is relatively constant, it continuously evolves in the coastal zone with the most prominent changes occurring in the Arctic. Although there are some quantitative estimations of different DOC loads to the Arctic fjords, their fate remains highly unknown. It is still unclear to what extent the DOC entering the fjords is bioavailable and how fast can it be remineralised. Therefore, the following research objectives have been formulated: to assess the lability of the terrigenous and sediment-derived DOC, and to estimate remineralization rate constants and half-life times for bioavailable DOC fractions. This has been done through the 180-days-lasting incubation experiments of soil leachates mixed with surface seawater and sediment interstitial waters mixed with bottom water. For the study site, Spitsbergen fjords have been selected. The results indicate that both the soil leachates and interstitial waters contain a lot of DOC (420-2730 μmol L^-1 and 220-470 μmol L^-1, respectively), which is highly bioavailable – the DOC decay observed during the experiments was 61-66% and 40-60%, respectively. This high lability of DOC indicates that its supply to the water column has the potential to play an essential role in sustaining the bacterial loop in the fjord and, through CO₂ release, in amplifying ocean acidification in the coastal zone. This knowledge is extremely desired as it allows for a better understanding of the processes shaping carbon cycling in the Arctic fjords.

Primary Presenter: Katarzyna Koziorowska-Makuch, Institute of Oceanology Polish Academy of Sciences (kkozio@iopan.gda.pl)

Authors:

Katarzyna Koziorowska-Makuch, Institute of Oceanology Polish Academy of Sciences  (kkozio@iopan.pl)

Fernando Aguado Gonzalo, Institute of Oceanology Polish Academy of Sciences  (aguadof@iopan.pl)

Laura Bromboszcz, Institute of Oceanology Polish Academy of Sciences  (laurab@iopan.pl)

Magdalena Diak, Institute of Oceanology Polish Academy of Sciences  (mdiak@iopan.pl)

Przemysław Makuch, Institute of Oceanology Polish Academy of Sciences  (makuch@iopan.pl)

Izabela Pałka, Institute of Oceanology Polish Academy of Sciences  (ipalka@iopan.pl)

Marcin Stokowski, Institute of Oceanology Polish Academy of Sciences  (stokowski@iopan.pl)

Beata Szymczycha, Institute of Oceanology Polish Academy of Sciences  (beatsz@iopan.pl)

Aleksandra Winogradow, Institute of Oceanology Polish Academy of Sciences  (aleksandra@iopan.pl)

Karol Kuliński, Institute of Oceanology Polish Academy of Sciences  (kroll@iopan.pl)