Fluorescent signatures of autochthonous dissolved organic matter production in Siberian shelf seas

Abstract

The East Siberian Sea is an area of high biogeochemical activity caused by multiple factors, such as an influence of river runoff, Atlantic, and Pacific waters, formation and melting of sea ice, and internal circulation. Extensive amounts of carbon are accumulated in sub-sea permafrost within the Arctic shelf in East Siberia. Thawing permafrost and resulting microbial decomposition of frozen carbon pool is a potential feedback process affected global climate dynamics. Several studies of dissolved organic carbon (DOC) distribution in the East Siberian Sea have demonstrated untypical for other Arctic shelf seas pronounced non-conservative DOC behavior. Using seawater samples from the 69th cruise of R/V Akademik Mstislav Keldysh conducted in the Laptev and East Siberian seas in September 2017, this study examines the distribution of fluorescent dissolved organic matter (FDOM) along the shelf-crossing transects including the areas affected by the Khatanga, Lena, Indigirka, and Kolyma river runoff. The set of 137 excitation-emission matrices (EEMs), analyzed with Parallel Factor analysis (PARAFAC), was described by a 4-component model demonstrating Tucker’s congruence coefficient above the 0.95 threshold. Spectral characteristics of the resulting components allowed identifying them as well-known humic-like A and C, protein-like B/T, and marine humic-like M fluorophores. Component C1 (A fluorophore) showed a good correlation with salinity for different river plume influenced regions. As well as chromophoric DOM (CDOM) absorption, it can be used as marker of input of terrestrial DOM to the Arctic Ocean. A distinctive feature of the East Siberian Sea shelf waters in comparison with the Laptev Sea is the higher content of the C2 and C4 components, exhibiting protein-like and marine humic-like fluorescence. Component C3 (C fluorophore) which is usually identified as terrestrial-derived material, was found to be produced locally on the East Siberian Sea shelf and in the continental slope region of the Khatanga transect. Destruction of dead algae cells, production of marine biota and dissolved organic matter (DOM) reworking are considered as possible autochthonous FDOM sources in the Siberian shelf seas.

Optical Insight Into Riverine Influences on Dissolved and Particulate Organic Carbon in a Coastal Arctic Lagoon System

“…Moreover, peak A (ex = 260 nm/em = 380-460 nm) is also commonly found in the source waters of this region (Ward & Cory, 2015) and represents a fluorescent pool within the bulk DOC that would not be detected by the commonly used commercial DOM fluorometer we employed in our field study. Allochthonous marine humic material, indicated by peak M (ex = 312 nm/em = 380-420 nm) and also often observed in coastal Arctic waters (Drozdova et al, 2022), may similarly be a portion of the DOC pool captured in our analytically measured DOC concentrations but spectrally invisible to the fluorometer used in this study.…”

Production of Fluorescent Dissolved Organic Matter by Microalgae Strains from the Ob and Yenisei Gulfs (Siberia)

“…In the recent study of Drozdova et al [ 66 , 67 ], the distribution of chlorophyll-a CDOM were analyzed in the river-influenced areas of Siberian shelf seas. The maximal chlorophyll-a concentrations were typical for the river plumes (salinity < 27).…”

Note on volume and distribution of fresh water in the Amazon River plume under low discharge conditions

“…Thus, in the Amazon River plume and the adjacent areas, a strong dilution of seawater water with river water was found to be a dominant process in shaping the conservative behavior of humic-like components along the salinity gradient (Hu et al 2004, Cao et al 2016. The conservative behaviour of some of independent fluorophores along the salinity gradient allow considering humic-like fluorescence as a tracer for terrestrial derived material refractory to bacterial utilization (i.e., Yamashita et al 2008, Drozdova et al 2022.…”