Preprints
https://doi.org/10.5194/bg-2021-249
https://doi.org/10.5194/bg-2021-249

  18 Oct 2021

18 Oct 2021

Review status: this preprint is currently under review for the journal BG.

Modeling of the large-scale nutrient biogeochemical cycles in Lake Onego

Oleg P. Savchuk1, Alexey V. Isaev2,3, and Nikolay N. Filatov2,3 Oleg P. Savchuk et al.
  • 1Baltic Nest Institute, Stockholm University Baltic Sea Centre, Stockholm, 10691, Sweden
  • 2Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, 117997, Russia
  • 3Northern Water Problems Institute, Karelian Research Center, Russian Academy of Sciences, Petrozavodsk, 185030, Russia

Abstract. Despite a long history of research, there is almost no information regarding the major biogeochemical fluxes that could characterize the past and present state of the European Lake Onego ecosystem and be used for reliable prognostic estimates of its future. To enable such capacity, we adapted and implemented a three-dimensional coupled hydrodynamical biogeochemical model of the nutrient cycles in Lake Onego. The model was used to reconstruct three decades of Lake Onego ecosystem dynamics with daily resolution on a 2 × 2 km grid. A comparison of available information from Lake Onego and other large boreal lakes proves that this hindcast is plausible enough to be used as a form of reanalysis. As new regional phenological knowledge, the reanalysis quantifies that the spring phytoplankton bloom, previously overlooked, reaches a maximum of 500 ± 128 mg C m−2 d−1 in May, contributes to approximately half of the lake’s annual primary production of 17.0–20.6 g C m−2 yr−1, and is triggered by increasing light availability rather than by an insignificant rise in water temperature. Coherent nutrient budgets provide reliable estimates of phosphorus and nitrogen residence times of 47 and 17 years, respectively. The shorter nitrogen residence time is explained by sediment denitrification, which in Lake Onego removes over 90 % of the bioavailable nitrogen input, but is often ignored in studies of other large lakes. This model can be used for long-term projections as soon as the corresponding scenarios of climate change and socio-economic development become available for north-western Russia.

Oleg P. Savchuk et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-249', Anonymous Referee #1, 29 Nov 2021
  • RC2: 'Comment on bg-2021-249', Anonymous Referee #2, 30 Nov 2021

Oleg P. Savchuk et al.

Oleg P. Savchuk et al.

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Short summary
Empirical information on the nutrient cycles in the second largest European Lake Onego is almost lacking. We covered the deficit by realistic simulation of the lake’s ecosystem dynamics during 1985–2015 with the 3D ecohydrodynamic model. Important results include: a) 3D dynamics of major nutrient variables and fluxes; b) quantification of the spring phytoplankton bloom, previously overlooked; c) coherent nutrient budgets. The model is a useful tool for forecasting with different scenarios.
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