Hydrochemical conditions and trophic status of the freshwater Curonian Lagoon

Authors

  • Aleksandrov S.V. 1
  • 1 Shirshov Institute of Oceanology, Russian Academy of Sciences, 36 Nakhimovskiy prospekt, Moscow, 117997, Russia

DOI:

https://doi.org/10.31951/2658-3518-2025-A-4-391

Keywords:

chlorophyll, nutrients, lagoon, algal bloom, trophic status, de-eutrophication

Abstract

The Curonian Lagoon is the largest lagoon in Europe with freshwater conditions. For a long period, a large amount of nutrients was supplied with the flow of the Neman River, which led to significant eutrophication of the lagoon. The consequence of this was a summer peak increase in phosphorus phosphates, associated with the intensive development of cyanobacteria and water “hyperblooming”. Comparison of data obtained in the southern part of the lagoon in 2019-2024 with an earlier period of water “blooming” (2007-2016) showed a 2-3-fold decrease in summer concentrations of phosphate phosphorus and a change in the N:P ratio (from <16 to ~30-50). As a result, the intensive development of cyanobacteria (water “hyperblooming”) ceased. During the period of water “hyperblooming” (2007-2016), chlorophyll a concentrations during the growing season and in summer exceeded 100 µg/l and characterized the Curonian Lagoon as a hypertrophic water body. In the modern period (2019-2024), chlorophyll a concentrations have decreased by 3-4 times (~40 µg/l). The decrease in chlorophyll and phosphorus concentrations in recent years can be characterized as significant de-eutrophication of the Curonian Lagoon.

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Published

2025-08-31

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Section

Articles