Abstract
Suspended particulate matter (SPM) and sediments were sampled in the Ob and the Yenisei rivers and the adjacent Kara Sea up to 77°N during the ice-free period in August and September 1997 (only sediments), 1999 and 2000. The material was analyzed for organic carbon (OC) and nitrogen (N) as well as for the content and monomeric composition of the labile organic constituents amino acids (AA) and amino sugars (AS). Despite interannual variation, surface SPM concentration generally revealed decreasing values from 8 to 4 mg/L for the Ob and Yenisei to values <0.5 mg/L in the offshore region reflecting the importance of fluvial input for SPM distribution. The quality of surface SPM was mainly determined by planktonic productivity as revealed by C/N, the content of AA+AS and their contribution to OC and N. Sedimentation caused a qualitative change of surface SPM at ∼ 73.5°N with POC-% averaging 6.7% south and 21% north of this latitude. This was accompanied by a change from 12–90 to 105–202 mg AA+AS/g SPM, respectively. Together with the monomeric composition of AA this indicates a higher reactivity of OM and a reduced dilution by detrital material in the offshore region. Whereas SPM was homogenously distributed in the rivers, the estuaries were characterized by a salt-wedge at depth. Deep water revealed highest SPM concentrations due to sediment resuspension and/or the presence of a nepheloid layer, which is mirrored in distinctively reduced OM content and reactivity relative to upper water column SPM. Compared to SPM, sediments are characterized by elevated contents of terrestrial OM in the southern study area especially off the Yenisei. OM content and reactivity decrease in offshore direction due to lower sedimentation rates and terrestrial OM input towards the north. The AA-derived reactivity index (RI) and degradation index (DI) together sensitively reflect the degradational stage of OM in SPM and sediments allowing a precise classification from fresh plankton-dominated SPM to degraded sediments. The information on organic carbon formation, recycling and preservation obtained during this study is a valuable contribution towards the assessment of an organic carbon budget for the investigated area.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.