Daily variation of prokaryotic community observed during spring season at the fixed-point research platform established in shelf waters of the East China Sea

Abstract

Prokaryotes play an important role in energy flux via food webs and biogeochemical cycles of carbon, nitrogen, phosphorus, sulfur and other elements in the ocean. In coastal waters adjacent to land, changes of prokaryotic compositions during spring bloom have been relatively well studied. Conversely, studies in offshore waters during spring season have been rarely conducted. In this study, daily observations of environmental and prokaryotic variables were carried out during ca. 2 months at the Ieodo Ocean Research Station located on shelf area of the East China Sea, to understand changes of prokaryotic dynamics during offshore spring bloom. Chlorophyll a concentrations varied from 0.6 to 5.8 &micro g L-1 during the study, indicating occurrence of a bloom in late April and early May. Prokaryotic abundances and production remained low in March and April, but showed an exponentially increasing pattern early in May. Alphaproteobacteria including SAR11 group were most dominant before algal bloom, but Flavobacteriia became the most dominant group ever since bloom. At the post-bloom period, Formosa belonging to Flavobacteriia and Verrucomicrobiae manifested to be one of dominant bacterial groups. The changing pattern of bacterial community composition during spring bloom in shelf area was generally similar to those found in coastal waters, suggesting that responses of bacterial community to algal bloom might be similar betwg spring bloom have been relatively well studied. Conversely, studies in offshore waters during spring season have been rarely conducted. In this study, daily observations of environmental and prokaryotic variables were carried out during ca. 2 months at the Ieodo Ocean Research Station located on shelf area of the East China Sea, to understand changes of prokaryotic dynamics during offshore spring bloom. Chlorophyll a concentrations varied from 0.6 to 5.8 &micro g L-1 during the study, indicating occurrence of a bloom in late April and early May. Prokaryotic abundances and production remained low in March and April, but showed an exponentially increasing pattern early in May. Alphaproteobacteria including SAR11 group were most dominant before algal bloom, but Flavobacteriia became the most dominant group ever since bloom. At the post-bloom period, Formosa belonging to Flavobacteriia and Verrucomicrobiae manifested to be one of dominant bacterial groups. The changing pattern of bacterial community composition during spring bloom in shelf area was generally similar to those found in coastal waters, suggesting that responses of bacterial community to algal bloom might be similar betw