Heterotrophic bacterial and <Emphasis Type="Italic">Synechococcus</Emphasis> spp. Growth and mortality along the inshore-offshore in the East China Sea in summer |
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Authors: | An-Yi Tsai Gwo-Ching Gong Robert W Sanders Kuo-Ping Chiang Chien-Fu Chao |
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Institution: | (1) Institute of Marine Environmental Chemistry and Ecology, National Taiwan Ocean University, Keelung, 202-24, Taiwan, ROC;(2) Center of Excellence for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan, ROC;(3) Department of Biology, Temple University, Philadelphia, PA 19122, USA;(4) Institute of Environmental Biology and Fishery Science, National Taiwan Ocean University, Keelung, 202-24, Taiwan, ROC |
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Abstract: | This study used the dilution method to examine growth and grazing rates of heterotrophic bacteria and an autotrophic picoplankton,
Synechococcus spp., from 1 to 11 July 2007 in the East China Sea. The main influence of oceanographic conditions in this aquatic system
was the introduction of fresh, high-nutrient water from Changjiang River and the extremely nutrient-poor, high-salinity waters
of Kuroshio Water. In these experiments, deviation from linearity in the relationship between dilution factor and net growth
rate was significant in a large number of cases. Growth rates for heterotrophic bacteria ranged from 0.024 to 0.24, and for
Synechococcus spp. from 0.03 to 0.21 h−1. Grazing rates ranged from 0.02 to 0.19 and 0.01 to 0.13 h−1, respectively. The spatial variations of Synechococcus spp. production to the primary production ratio (SP/PP) were low (<5%) in high Chl a environments and increased exponentially in low Chl a environments, indicating that Synechococcus spp. contributes to a large extent to the photosynthetic biomass in the open sea, especially in the more oligotrophic Kuroshio
Water. Furthermore, the results of our dilution experiments suggest that nanoflagellates largely depend on heterotrophic bacteria
as an important energy source. On average, heterotrophic bacteria contributes to 76 and 59% of carbon consumed by nanoflagellates
within the plume (salinity <31) and outside of it (salinity >31). |
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