Bathymetric trends in biomass size spectra, carbon demand, and production of Arctic benthos (76-5561 m, Fram Strait)


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Thomas.Soltwedel [ at ] awi.de

Abstract

This is the first study to present the patterns and environmental controls of benthic biomass size spectra, carbon demand, and production along the entire bathymetric gradient from the shelf to the abyssal depths in the Arctic Ocean. The materials were collected at 17 stations (76 - 5561 m) in the eastern Fram Strait, in the Atlantic passage to the Arctic Ocean, in the vicinity of the productive Marginal Ice Zone, with concentrations of sediment-bound chloroplastic pigments (indicating food availability from phytodetritus sedimentation) higher than in other deep-sea localities at similar depths. Meiobenthic and macrobenthic individuals were measured using image analysis to assess their biovolume, biomass, annual production, and carbon demand. Benthic biomass in the area was clearly higher than that in the High Arctic locations and comparable to that in the lower-latitude North Atlantic. Biomass and annual production were significantly negatively correlated with water depth, with stronger bathymetric clines in macrofauna than in meiofauna and the increasing dominance of meiofauna with increasing depth. A bimodal shape in the size spectra was observed only at the shallow stations, while at depths below 2000 m, an additional trough was present in the macrofaunal part of the spectrum. The entire range of the spectra (i.e., the number of size classes) decreased with increasing depth, especially in the macrofaunal part of the spectrum. Similar slope values in the normalized spectra indicated that the distribution of the biomass across the present size classes was consistent from the shelf to the abyssal depths, irrespective of the decreasing amount of food availability. The fragmented macrofaunal size spectra documented at the two stations were probably due to physical disturbances at the sediment-water interface (e.g., intense bioturbation of holothurians and strong near-bottom currents). Benthic carbon demand declined from 50.7 gC m-2 y-1 at the shelf to 11.5 gC m-2 y-1 at the slope to 2.2 gC m-2 y-1 at the abyssal depths, and its partitioning among meiofauna and macrofauna changed with water depth, with meiofauna contributions increasing from 50 % at the shelf to over 90 % at the deepest station. The estimated total benthic carbon demand exceeded the vertical Corg fluxes, suggesting that the studied system can be particularly sensitive to future changes in productivity regimes and associated organic matter fluxes.



Item Type
Article
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Primary Division
Programs
Primary Topic
Research Networks
Peer revision
ISI/Scopus peer-reviewed
Publication Status
Published
Eprint ID
49808
DOI 10.1016/j.pocean.2020.102370

Cite as
Gorska, B. , Soltwedel, T. , Schewe, I. and Wlodarska-Kowalczuk, M. (2020): Bathymetric trends in biomass size spectra, carbon demand, and production of Arctic benthos (76-5561 m, Fram Strait) , Progress In Oceanography, 186 . doi: 10.1016/j.pocean.2020.102370


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