The turbidity maximum zone of the Yenisei River (Siberia) and its impact on organic and inorganic proxies

A general overview of the processes taking place in the summer mixing zone of the fresh Yenisei River water with the marine waters of the Kara Sea is given in this study, with special emphasis on the interaction between bulk (total suspended matter), inorganic (Fe, Mn) and organic (suspended organic carbon, suspended nitrogen) proxies. Within the mixing zone, a zone of enhanced turbidity (maximum turbidity zone) was observed comparable to studies in other rivers. Flocculation of particles due to changes in salinity and hydrography cause this maximum turbidity zone, and resuspension additionally enhances the turbidity in the near-bottom layers. Organic matter behaves conservatively in the mixing zone in terms of its percentage of suspended matter. It, however, undergoes degradation as revealed by amino acid data. Inorganic, redox- and salinity-sensitive, proxies (Mn, Fe) behave non-conservatively. Dissolved iron is removed at low salinities (<2) due to precipitation of iron oxyhydroxides and adsorption of manganese on suspended particles, enhancing the Mn/Al ratio of the suspended matter in the same zone. At higher salinities within the mixing zone, Fe/Al and Mn/Al ratios of the suspended particles are depleted due to resuspension of sediment with lower Fe/Al and Mn/Al ratios. Dissolved manganese concentrations are significantly higher in the near-bottom layers of the mixing zone due to release from the anoxic sediment. All things considered, the Yenisei River mixing zone shows patterns similar to other world's rivers

Physical oceanography during METEOR cruise M74/1b

Gaye, Birgit (2007): Hydrographic observations in the Arabian Sea during Meteor cruise 74/1b from 19. September - 4. October 2007

Particulate matter fluxes in the southern and central Kara Sea compared to sediments: Bulk fluxes, amino acids, stable carbon and nitrogen isotopes, sterols and fatty acids.

The Kara Sea is one of the arctic marginal seas strongly influenced by fresh water and river suspension. The highlyseasonal discharge by the two major rivers Yenisei and Ob induces seasonal changes in hydrography, sea surfacetemperature, ice cover, primary production and sedimentation. In order to obtain a seasonal pattern of sedimentation inthe Kara Sea, sediment traps were deployed near the river mouth of the Yenisei (Yen) as well as in the central Kara Sea(Kara) within the framework of the GermanRussian project Siberian River run-off; SIRRO. Two and a half years oftime-series flux data were obtained between September 2000 and April 2003 and were analyzed for bulk components,amino acids, stable carbon and nitrogen isotopes as well as sterols and fatty acids.Sediment trap data show that much of the annual deposition occurred under ice cover, possibly enhanced byzooplanktonic activity and sediment resuspension. An early bloom of ice-associated algae in April/May occurred in thepolynya area and may have been very important to sustain the life cycles of higher organisms after the light limitation ofthe winter months due to no/low insolation and ice cover. The strong river input dominated the months JuneAugust inthe southern part of the Kara Sea. The central Kara Sea had a much shorter productive period starting in August and wasless affected by the river plumes. Despite different time-scales of sampling and trapping biases, total annual fluxes fromtraps were in the same order of magnitude as accumulation rates in surface sediments. Terrestrial organic carbonaccumulation decreased from 10.7 to 0.3 gCm 2 a 1 from the riverine source to the central Kara Sea. Parallel to this,preservation of marine organic matter decreased from 10% to 2% of primary productivity which was probably related todecreasing rates of sedimentation

Particle analysis in the Kara Sea

In September 1999 two short-term moorings with cylindrical sediment traps were deployed to collect sinking particles in bottom waters off the Ob and Yenisei river mouths. Samples were studied for their bulk composition, pigments, phytoplankton, microzooplankton, fecal material, amino acids, hexosamines, fatty acids and sterols and compared to suspended matter and surface sediments in order to collect information about the nature and cycling of particulate matter in the water column. Results of all measured components in sinking particles point to an ongoing seasonality in the pelagic system from blooming diatoms in the first phase to a more retention system in the second half of trap deployment. Due to a phytoplankton bloom observed north of the Ob estuary, flux rates were generally higher in the trap deployed off the Ob than off the Yenisei. The Ob trap collected fresh surface-derived particulate matter. Particles from the Yenisei trap were more degraded and resembled deep water suspension. This material may partly have been derived from resuspended sediments

Biomarker flux of short-time sediment trap BP99-03

Biomarker flux of short-time sediment trap BP99-0

Organic suspended matter in Kara Sea of short-time sediment trap BP99-01

Organic suspended matter in Kara Sea of short-time sediment trap BP99-0

Stable isotopes in surface sediments from the Ob and Yenisei estuaries and the southern Kara Sea

Stable isotopes in surface sediments from the Ob and Yenisei estuaries and the southern Kara Se