Shifting spring phytoplankton blooms in the Baltic Sea

A new publication shows that spring phytoplankton blooms occur 1-2 weeks earlier over the last 20 years in the central Baltic Sea. Warmer temperature advance timing of diatom and dinoflagellates, the two dominant taxonomic groups of the spring bloom, and decrease bloom magnitude. Bloom timing of the entire species composition was, however, buffered by a temperature and ice related shift in composition from early blooming diatoms to later blooming dinoflagellates and the autotrophic ciliate Mesodinium rubrum.

A shift from early blooming and fast sedimenting diatoms to later blooming flagellated groups at higher temperature is expected to increase energy transfers to pelagic secondary production and decrease spring bloom inputs to the benthic system.

Spring phytoplankton blooms contribute a substantial part to annual production, support pelagic and benthic secondary production and influence biogeochemical cycles. Understanding environmental effects on spring bloom dynamics is important for predicting future climate responses for managing aquatic systems.

The full publication is available at:

Hjerne O, Hajdu S, Larsson U, Downing A, Winder M (2019) Climate Driven Changes in Timing, Composition and Magnitude of the Baltic Sea Phytoplankton Spring Bloom. Frontiers in Marine Science. 6.

Seasonal biomass dynamics of major phytoplankton groups in the Baltic Sea


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