AUTHOR=Lengier Monika , Koziorowska-Makuch Katarzyna , Szymczycha Beata , Kuliński Karol 

TITLE=Bioavailability and remineralization rates of sediment-derived dissolved organic carbon from a Baltic Sea depositional area

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 11 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2024.1359563

DOI=10.3389/fmars.2024.1359563

ISSN=2296-7745

ABSTRACT=This pilot study investigated the bioavailability and remineralization kinetics of the sediment-derived dissolved organic carbon (DOC) from the Gdańsk Deep, a depositional area in the Baltic Sea. This was assessed in the long-lasting (126 days) incubation experiment, in which the mixture of DOC from sediment pore water and bottom water was exposed to oxic microbial respiration with incubation of bottom water as a control run. The obtained decay curves allowed us to distinguish three DOC fractions: labile (DOCL), semi-labile (DOCSL), and refractory (DOCR). In bottom water, the refractory fraction was predominant and amounted to almost 85% of total DOC, while about 15% of DOC was bioavailable: 6% labile and 9% semi-labile. In contrast, DOC from pore water was much more bioavailable DOC (~55% of total DOC) and contained 11% DOCL and 44% DOCSL. The remineralization rate constants recalculated to the in situ temperature of 6°C for labile and semi-labile DOC in pore water were 0.025d -1 and 0.002d -1 , respectively, while in bottom water: 0.026d -1 and 0.004d -1 . The half-life times for DOCL were comparable for both bottom water and pore water and amounted to 26.2d and 27.6d, respectively. For DOCSL the half-life time was shorter for bottom water (165.5d) than for pore water (322.9d).