Dataset Information

Bacterial contribution to dissolved organic matter in eutrophic Lake Kasumigaura, Japan.

ABSTRACT: Incubation experiments using filtered waters from Lake Kasumigaura were conducted to examine bacterial contribution to a dissolved organic carbon (DOC) pool. Bacterial abundance, bacterial production, concentrations of DOC, total dissolved amino acids (TDAA), and total dissolved neutral sugars (TDNS) were monitored during the experiments. Bacterial production during the first few days was very high (20 to 35 ?g C liter(-1) day(-1)), accounting for 40 to 70% of primary production. The total bacterial production accounted for 34 to 55% of the DOC loss during the experiment, indicating high bacterial activities in Lake Kasumigaura. The DOC degradation was only 12 to 15%, whereas the degradation of TDAA and TDNS ranged from 30 to 50%, suggesting the preferential usage of TDAA and TDNS. The contribution of bacterially derived carbon to a DOC pool in Lake Kasumigaura was estimated using d-amino acids as bacterial biomarkers and accounted for 30 to 50% of the lake DOC. These values were much higher than those estimated for the open ocean (20 to 30%). The ratio of bacterially derived carbon to bulk carbon increased slightly with time, suggesting that the bacterially derived carbon is more resistant to microbial degradation than bulk carbon. This is the first study to estimate the bacterial contribution to a DOC pool in freshwater environments. These results indicate that bacteria play even more important roles in carbon cycles in freshwater environments than in open oceans and also suggests that recent increases in recalcitrant DOC in various lakes could be attributed to bacterially derived carbon. The potential differences in bacterial contributions to dissolved organic matter (DOM) between freshwater and marine environments are discussed.

SUBMITTER: Kawasaki N

PROVIDER: S-EPMC3837723 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Bacterial contribution to dissolved organic matter in eutrophic Lake Kasumigaura, Japan.

Kawasaki Nobuyuki N Komatsu Kazuhiro K Kohzu Ayato A Tomioka Noriko N Shinohara Ryuichiro R Satou Takayuki T Watanabe Fumiko Nara FN Tada Yuya Y Hamasaki Koji K Kushairi M R M MR Imai Akio A

Applied and environmental microbiology 20130913 23

Incubation experiments using filtered waters from Lake Kasumigaura were conducted to examine bacterial contribution to a dissolved organic carbon (DOC) pool. Bacterial abundance, bacterial production, concentrations of DOC, total dissolved amino acids (TDAA), and total dissolved neutral sugars (TDNS) were monitored during the experiments. Bacterial production during the first few days was very high (20 to 35 μg C liter(-1) day(-1)), accounting for 40 to 70% of primary production. The total bacte ...[more]

PMID: 24038686

Similar Datasets

Project description:The biodegradability of terrigenous dissolved organic matter (tDOM) exported to the sea has a major impact on the global carbon cycle, but our understanding of tDOM bioavailability is fragmentary. In this study, the effects of preparative tDOM isolation on microbial decomposition were investigated in incubation experiments consisting of mesocosms containing mesohaline water from the Baltic Sea. Dissolved organic carbon (DOC) consumption, molecular DOM composition, bacterial activities, and shifts in bacterial community structure were compared between mesocosms supplemented with riverine tDOM, either as filtered, particle-free river water or as a concentrate obtained by lyophilization/tangential ultrafiltration, and those containing only Baltic Sea water or river water. As shown using ultra-high-resolution mass spectrometry (15 Tesla Fourier-transform ion cyclotron resonance mass spectrometry, FT-ICR-MS) covering approximately 4600 different DOM compounds, the three DOM preparation protocols resulted in distinct patterns of molecular DOM composition. However, despite DOC losses of 4-16% and considerable bacterial production, there was no significant change in DOM composition during the 28-day experiment. Moreover, tDOM addition affected neither DOC degradation nor bacterial dynamics significantly, regardless of the tDOM preparation. This result suggested that the introduced tDOM was largely not bioavailable, at least on the temporal scale of our experiment, and that the observed bacterial activity and DOC decomposition mainly reflected the degradation of unknown, labile, colloidal and low-molecular weight DOM, both of which escape the analytical window of FT-ICR-MS. In contrast to the different tDOM preparations, the initial bacterial inoculum and batch culture conditions determined bacterial community succession and superseded the effects of tDOM addition. The uncoupling of tDOM and bacterial dynamics suggests that mesohaline bacterial communities cannot efficiently utilize tDOM and that in subarctic estuaries other factors are responsible for the removal of imported tDOM.

Project description:Marine dissolved organic matter (DOM) is a complex mixture of chemical compounds. At 750 Pg C, it is one of the biggest pools of reduced carbon on Earth. It has been proposed that the diversity of DOM is responsible for its recalcitrance. We hypothesize that the chemodiversity of marine DOM is a reflection of the chemodiversity of bacterial exometabolomes. To test this, we incubated two model strains of the Roseobacter group; Phaeobacter inhibens and Dinoroseobacter shibae in pure culture using three different simple organic compounds as sole carbon sources (glutamate, glucose, and acetate and succinate for P. inhibens and D. shibae, respectively). The exometabolome of the model organisms was characterized using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) and ecological diversity measures. We detected thousands of molecular masses in the exometabolomes of P. inhibens and D. shibae (21,105 and 9,386, respectively), reflecting the capability of single bacterial strains to diversify simple organic compounds. The chemical composition of the exometabolomes changed with growth phase and also differed according to the strain incubated and the utilized substrate. We mimicked a higher diversity of substrates, bacterial species and heterogeneous growth (different growth phases) to approach the complexity of natural environments, by computationally creating combinations of detected exometabolomes. We compared the chemodiversity of these combinations, indicative for chemodiversity of freshly produced microbial DOM to that of refractory DOM from one of the oldest oceanic water masses (North Equatorial Pacific Intermediate Water). Some combinations of exometabolomes showed higher richness than the deep ocean refractory DOM, and all the combinations showed higher functional diversity. About 15% of the 13,509 molecular formulae detected in exometabolomes and refractory oceanic DOM were shared, i.e., occurred in Roseobacter exometabolomes and in deep water samples. This overlap provides further support for our hypothesis that marine bacteria from the Roseobacter group contribute to the sustainability of marine DOM chemodiversity and stability.

Project description:Dissolved organic phosphorus (DOP) is an important nutrient for phytoplankton growth in oligotrophic oceans. However, little is known about the impact of DOP on phytoplankton growth in eutrophic waters. In the present study, we conducted field monitoring as well as in situ and laboratory experiments in the Pearl River estuary (PRE). Field observations showed an increase in the nitrogen-to-phosphorus ratio and DOP in recent years in the PRE. The phytoplankton community was dominated by nanophytoplankton Cyclotella in the upper and middle estuary, with high concentrations of DOP and light limitation during the ebb stage of the spring to neap tide in summer. The relative abundance of Cyclotella in natural waters was higher after enrichment with estuarine water with a background of 0.40-0.46 µM DOP, even when dissolved inorganic phosphorus was sufficient (0.55-0.76 µM). In addition, the relative abundance of Cyclotella in natural waters was higher after enrichment with phosphoesters. Laboratory culture results also confirmed that phosphoesters can enhance the growth rate of Cyclotella cryptica. Our study highlights that Cyclotella can become the dominant species in estuaries with increased levels of phosphoesters and low and fluctuating light adaptability and under the joint effect of dynamic processes such as upwelling and tides. Our results provide new insights into the role of Cyclotella in biogeochemical cycles affected by DOP utilization and potential applications in relieving the hypoxia of tropical eutrophic estuaries.IMPORTANCEThis study provides evidence that Cyclotella can become the dominant species in estuaries with increased levels of phosphoesters and low and fluctuating light adaptability and under the joint effect of dynamic processes such as upwelling and tides. Our study provides new insights into the role of Cyclotella in biogeochemical cycles affected by dissolved organic phosphorus utilization, especially affected by anthropogenic inputs and climate change. Potential applications include relieving the hypoxia of tropical eutrophic estuaries.

Dataset Information

Bacterial contribution to dissolved organic matter in eutrophic Lake Kasumigaura, Japan.

Publications

Bacterial contribution to dissolved organic matter in eutrophic Lake Kasumigaura, Japan.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets