Spring blooms in the Baltic Sea have weakened but lengthened from 2000 to 2014

P.M.M. Groetsch, S.G.H. Simis, M.A. Eleveld, S.W.M. Peters

Research output: Contribution to JournalArticleAcademicpeer-review


Phytoplankton spring bloom phenology was derived from a 15-year time series (2000-2014) of ship-of-opportunity chlorophyll a fluorescence observations collected in the Baltic Sea through the Alg@line network. Decadal trends were analysed against inter-annual variability in bloom timing and intensity, and environmental drivers (nutrient concentration, temperature, radiation level, wind speed). Spring blooms developed from the south to the north, with the first blooms peaking mid-March in the Bay of Mecklenburg and the latest bloom peaks occurring mid-April in the Gulf of Finland. Bloom duration was similar between sea areas (43 ± 2 day), except for shorter bloom duration in the Bay of Mecklenburg (36 ± 11 day). Variability in bloom timing increased towards the south. Bloom peak chlorophyll a concentrations were highest (and most variable) in the Gulf of Finland (20.2 ± 5.7 mg m
Original languageEnglish
Pages (from-to)4959-4973
Publication statusPublished - 2016


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