Seasonal changes of dissolved and particulate organic carbon in Donghu Lake, China

2000 ◽  
Vol 18 (4) ◽  
pp. 372-377 ◽  
Author(s):  
Liu Xue-jun ◽  
Xu Xiao-qing ◽  
Xie Ping ◽  
Noriko Takamura
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Seasonal Changes ◽  
Donghu Lake

Seasonal changes in heterotrophic bacteria under fast ice near Syowa station, Antarctica

1989 ◽  
Vol 35 (2) ◽  
pp. 329-333 ◽  
Author(s):  
Hiroo Satoh ◽  
Kimio Fukami ◽  
Kentaroo Watanabe ◽  
Eiji Takahashi
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Seasonal Changes ◽  
Heterotrophic Bacteria ◽  
Seasonal Succession ◽  
Austral Spring ◽  
Syowa Station ◽  
Colony Forming Units ◽  
Algal Assemblages ◽  
Fast Ice

Seasonal changes in the number of heterotrophic bacteria and the species composition of their communities were investigated in the fast ice area of Syowa station (69°00′S, 39°35′E), from May 1983 to January 1984. Numbers of heterotrophic bacteria under the fast ice began to increase in October and the maximum number of colony-forming units/mL (2.4 × 102) were obtained in late December. The changes in bacterial numbers coincided well with those of particulate organic carbon, suggesting that the growth of heterotrophic bacteria depends on the supply of particulate organic carbon from ice algal assemblages which grow rapidly at the bottom of sea ice during the austral spring. Vibrionaceans in the communities in September accounted for as much as 35% of the isolates, whereas in December, they were not detected at all. These results indicate that there is a seasonal succession in the bacterial communities between September and December.Key words: heterotrophic bacteria, vibrionaceans, fast ice, Antarctica.

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

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