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Marine Ecology Progress Series

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MEPS 446:61-71 (2012)  -  DOI:

Experimental induction of a coastal spring bloom early in the year by intermittent high-light episodes

Ulrich Sommer1,*, Kathrin Lengfellner2, Aleksandra Lewandowska1

1Helmholtz Center for Ocean Resarch (GEOMAR), Düsternbrooker Weg 20, 24105 Kiel, Germany
2Ecology and Environmental Sciences, University of Umeå, 901 87 Umeå, Sweden

ABSTRACT: Through the use of mesocosm experiments, we show that an unusually early spring phytoplankton bloom can be induced by intermittent high-light periods. We performed mesocosm experiments where plankton assemblages from Kiel Bight (Western Baltic Sea) received a light regime based on the natural seasonal irradiance dimmed to 43% of surface irradiance of cloudless days, starting with irradiance levels of mid-January (6 mesocosms) and mid-February (6 mesocosms). After 6 d, half of the mesocosms received a ca. 2-fold increase in irradiance. In the January mesocosms, a phytoplankton bloom developed only in the treatments with the high-light episode, whereas in the February mesocosms a phytoplankton bloom also developed in the controls. Phytoplankton net growth rates, production:biomass ratios and biomass at the end of the high irradiance episodes were positively correlated to the daily light dose. The relative biomass of diatoms increased with increasing light, whereas the relative biomass of cryptophytes decreased. A bottom-up transmission to mesozooplankton (mainly copepods of the genera Acartia and Oithona) was evident by increased densities of copepod nauplii and egg production under higher light conditions, whereas copepodids and adults showed no responses during the experimental period. The taxonomic composition of the nauplii was shifted to the advantage of Acartia/Centropages (not distinguished at the naupliar stage) under higher light conditions.

KEY WORDS: Plankton · Spring bloom · Irradiance

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Cite this article as: Sommer U, Lengfellner K, Lewandowska A (2012) Experimental induction of a coastal spring bloom early in the year by intermittent high-light episodes. Mar Ecol Prog Ser 446:61-71.

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