EGU2020-10101
https://doi.org/10.5194/egusphere-egu2020-10101
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

CDOM Absorption Properties of Natural Water Bodies Along Extreme Environmental Gradients

Jakob J. Stamnes1, Ciren Nima2, Børge Hamre1, Øyvind Frette1, Yi-Chun Chen1, Kai Sørensen3, Marit Norli3, Daren Lu4, Qiangguo Xing5, Dennis Muyiimbwa6, Taddeo Ssenyyonga6, Knut Stamnes7, and Svein Rune Erga1
Jakob J. Stamnes et al.
  • 1University of Bergen, Bergen, Norway
  • 2Tibet University, Department of Physics, Lhasa, China
  • 3Norwegian Institute for Water Research, Oslo, Norway
  • 4Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 5Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
  • 6Makerere University, Department of Physics, Uganda
  • 7Stevens Institute of Technology, 1 Castle Point on Hudson, Hoboken, NJ 07030, USA

We present absorption properties of colored dissolved organic matter (CDOM) sampled in six different water bodies along extreme altitudinal, latitudinal, and trophic state gradients. Three sites are in Norway: the mesotrophic Lysefjord (LF), Samnangerfjord (SF), and Røst Coastal Water (RCW); two sites are in China: the oligotrophic Lake Namtso (LN) and the eutrophic Bohai Sea (BS); and one site is in Uganda: the eutrophic Lake Victoria (LV).

 

The site locations ranged from equatorial to subarctic regions, and they included water types from oligotrophic to eutrophic and altitudes from 0 m to 4700 m. The mean CDOM absorption coefficients at 440 nm [aCDOM(440)] and 320 nm [aCDOM(320)] varied in the ranges 0.063–0.35 m-1 and 0.34–2.28 m-1, respectively, with highest values in LV, Uganda and the lowest in the high-altitude LN, Tibet.

 

The mean spectral slopes S280-500 and S350-500 were found to vary in the ranges of 0.017–0.032 nm-1 and 0.013–0.015 nm-1, respectively. The highest mean value for S280-500 as well as the lowest mean value for S350-500 were found in LN. Scatter plots of S280-500 versus aCDOM(440) and aCDOM(320) values ranges revealed a close connection between RCW, LF, and SF on one side, and BS and LV on the other side.

 

CDOM seems to originate from terrestrial sources in LF, SF, BS, and LV, while RCW is characterized by autochthonous-oceanic CDOM, and LN by autochthonous CDOM. Photobleaching of CDOM is prominent in LN, demonstrated by absorption towards lower wavelengths in the UV spectrum. We conclude that high altitudes, implying high levels of UV radiation and oligotrophic water conditions are most important for making a significant change in CDOM absorption properties.

Considering all study sites, we find a strong negative linear relationship between the base-10 logarithm of aCDOM(440) and the spectral slope S280-500, and also between the base-10 logarithm of aCDOM(320) and the spectral slope S280-500.

How to cite: Stamnes, J. J., Nima, C., Hamre, B., Frette, Ø., Chen, Y.-C., Sørensen, K., Norli, M., Lu, D., Xing, Q., Muyiimbwa, D., Ssenyyonga, T., Stamnes, K., and Erga, S. R.: CDOM Absorption Properties of Natural Water Bodies Along Extreme Environmental Gradients, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10101, https://doi.org/10.5194/egusphere-egu2020-10101, 2020