Simultaneous estimates ofsynechococcus spp. Growth and grazing mortality rates in the English Channel |
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| Authors: | Ning Xiu-ren Daniel Vaulot |
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| Institution: | (1) Second Institute of Oceanography, SOA, 310012 Hangzhou;(2) Station Biologique de Roscoff, CNRS, 29680 Roscoff, France |
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| Abstract: | The marine chroococooid phycoerythrin-containingSynechococcus spp. cyanobacterium has been implicated as a substantial component of the photosynthetic picoplankton in the ocean. Although
its importance as food source for heterotrophic nanoplankton is now recognized, information about the cycling ofSynechococcus biomass and its diel pattern is limited and study methodology varies among authors. The selective metabolic inhibitor method
was used to simultaneously estimate growth and grazing disappearance rates ofSynechococcus in the English Channel where growth rates ranged from 0.25 to 0.72/d (mean ±SD=0.51±0.17/d) and grazing mortality rates ranged
from 0.19 to 0.64/d (mean ±SD=0.48±0.17/d). Size-fractionated experiments demonstrated that up to 70% ofSynechococcus disappearance could be attributed to grazers going through a 2 μm Nuclepore filter.Synechococcus grazing mortality rates (mean=0.74 ±0.25/d) during the day were always higher than that (mean=0.2±0.20/d) during the night,
while growth rates showed no clear diel pattern. A positive correlation was observed between growth rates andin situ temperature ranging from 9 to 17°C, while in contrast grazing was independent of temperature. The close similatiry between
average growth and grazing rates suggests a rapid recycling ofSynechococcus biomass in English Channel coastal waters. |
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| Keywords: | photosynthetic picoplankton cyanobacteria Synechococcus spp growth and grazing mortality English Channel |
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