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Effects of dissolved organic matter and temperature on the bacterial community during spring
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
Abstract [en]

Marine bacteria are the main driver in marine ecosystem and the microbial loop in the seawater has been a hot topic in marine science in last decades. Since, there have been some long time-scale monitoring studies about bacterial dynamics in temperate water. Studies about interactions among marine bacteria, dissolved organic matter (DOM) and seawater temperature are still rare. In order to understand more details, a two-factor experiment (DOM added or not, and at 4 °C or 8 °C) was settled after a phytoplankton mesocosm, including the measurements of bacterial abundance (BA), extracellular enzyme activities (EEA) and bacterial activities (including bacterial production (BP), respiration (BR) and growth efficiency (BGE)), as well as 16S rRNA gene sequencing. The water samples for mesocosm were from the harbor near to Kocken, Linnaeus University, Kalmar, south of Sweden. The inoculum of phytoplankton and bacteria, and the water samples for bacteria cultures were from the LMO station. The result of the experiment showed that during experiment period, the most abundant bacteria were Gammaproteobacteria, and Alphaproteobacteria, Bacteroidetes and Betaproteobacteria were secondly abundant. There were significant differences in enzyme activities; BP showed significant differences only in the treatment with adding DOM; no difference in BR was found in 3 µm pore-size filter but it was found significantly different in treatment LD compared to treatments without DOM added in 0.2 µm pore-size filter. Treatment LD (4 °C and DOM added) had statistically significant differences in BGE compared to other treatments. The conclusion was that the change of temperature and DOM concentration resulted in a change of both bacterial growth and community composition. The bacteria were more abundant after adding fresh DOM than those without extra DOM, and at lower temperature, it took longer time for BA to reach to the same abundances in the exponential phase. When the DOM concentration was high, temperature had synergistic effects on the bacterial community. In contrast, when the DOM concentration was low, the influence of temperature was not significant. The bacterial community composition only changed when both temperature DOM concentration were higher. Otherwise, either temperature or DOM concentration was not significant effect on the composition of bacterial community. This studies indicated more information about the bacterial dynamics in the south Baltic Sea in spring according to the seasonal change. Further studies can be focused on a longer-period experiment on bacterial community so that we can get a seasonal blue print of the marine bacteria community dynamic change in the Baltic Sea.

Place, publisher, year, edition, pages
2016. , 30 p.
National Category
Ecology
Identifiers
URN: urn:nbn:se:lnu:diva-56469OAI: oai:DiVA.org:lnu-56469DiVA: diva2:968671
Subject / course
Biology
Educational program
Akvatisk ekologi, masterprogram, 120 hp
Supervisors
Examiners
Available from: 2016-09-14 Created: 2016-09-12 Last updated: 2016-09-14Bibliographically approved

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Citation style
  • apa
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