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Effect of resource availability on bacterial community responses to increased temperature
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Kalmar, Sweden.
Kalmar, Sweden; Helsingör, Denmark.
Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. (Arcum)
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2013 (English)In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 68, no 2, 131-142 p.Article in journal (Refereed) Published
Abstract [en]

Climate change is predicted to cause higher temperatures and increased precipitation, resulting in increased inflow of nutrients to coastal waters in northern Europe. This has been assumed to increase the overall heterotrophy, including enhanced bacterial growth. However, the relative importance of temperature, resource availability and bacterial community composition for the bacterial growth response is poorly understood. In the present study, we investigated effects of increased temperature on bacterial growth in waters supplemented with different nutrient concentrations and inoculated with microbial communities from distinct seasonal periods. Seven experiments were performed in the northern Baltic Sea spanning an entire annual cycle. In each experiment, bacterioplankton were exposed to 2 temperature regimes (in situ and in situ + 4 degrees C) and 5 nutrient concentrations. Generally, elevated temperature and higher nutrient levels caused an increase in the bacterial growth rate and a shortening of the response time (lag phase). However, at the lowest nutrient concentration, bacterial growth was low at all tested temperatures, implying a stronger dependence on resource availability than on temperature for bacterial growth. Furthermore, data indicated that different bacterial assemblages had varying temperature responses and that community composition was strongly affected by the combination of high nutrient addition and high temperature. These results support the concern that climate change will promote heterotrophy in aquatic systems, where nutrient levels will increase considerably. In such environments, the bacterial community composition will change, their growth rates will increase, and their response time will be shortened compared to the present situation.

Place, publisher, year, edition, pages
Inter-Research , 2013. Vol. 68, no 2, 131-142 p.
Keyword [en]
Temperature increase, Resource availability, Bacterial growth response, Climate change, Community dynamics
National Category
URN: urn:nbn:se:umu:diva-67607DOI: 10.3354/ame01609ISI: 000315598900004OAI: diva2:622630
Available from: 2013-05-22 Created: 2013-03-25 Last updated: 2016-05-20Bibliographically approved
In thesis
1. Response of marine food webs to climate-induced changes in temperature and inflow of allochthonous organic matter
Open this publication in new window or tab >>Response of marine food webs to climate-induced changes in temperature and inflow of allochthonous organic matter
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Global records of temperature show a warming trend both in the atmosphere and in the oceans. Current climate change scenarios indicate that global temperature will continue to increase in the future. The effects will however be very different in different geographic regions. In northern Europe precipitation is projected to increase along with temperature. Increased precipitation will lead to higher river discharge to the Baltic Sea, which will be accompanied by higher inflow of allochthonous organic matter (ADOM) from the terrestrial system. Both changes in temperature and ADOM may affect community composition, altering the ratio between heterotrophic and autotrophic organisms. Climate changes may thus have severe and complex effects in the Baltic Sea, which has low species diversity and is highly vulnerable to environmental change. The aim of my thesis was to acquire a conceptual understanding of aquatic food web responses to increased temperature and inputs of ADOM. These factors were chosen to reflect plausible climate change scenarios. I performed microcosm and mesocosm experiments as well as a theoretical modeling study. My studies had a holistic approach as they covered entire food webs, from bacteria and phytoplankton to planktivorous fish. The results indicate a strong positive effect of increased temperature and ADOM input on the bacterial community and the microbial food web. However, at the prevailing naturally low nutrient concentrations in the Baltic Sea, the effect of increased temperature may be hampered by nutrient deficiency. In general my results show that inputs of ADOM will cause an increase of the bacterial production. This in turn can negatively affect the production at higher trophic levels, due to establishment of an intermediate trophic level, consisting of protozoa. However, the described effects can be counteracted by a number of factors, as for example the relatively high temperature optimum of fish, which will lead to a more efficient exploitation of the system. Furthermore, the length of the food web was observed to be a strong regulating factor for food web responses and ecosystem functioning. Hence, the effect of environmental changes may differ quite drastically depending on the number of trophic levels and community composition of the system. The results of my thesis are of importance as they predict possible ecological consequences of climate change, and as they also demonstrate that variables cannot be examined separately.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2015. 28 p.
Climate change, bacterial production, mesocosm, food web efficiency, Baltic Sea
National Category
urn:nbn:se:umu:diva-102791 (URN)978-91-7601-266-6 (ISBN)
Public defence
2015-05-28, KBC-huset, Lilla Hörsalen, KB3A9, Umeå universitet, Umeå, 10:00
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGESwedish Research Council Formas, AA and SL (217-2006-674)

This thesis was supported by grants from the Swedish Research Council FORMAS to AA and SL (217-2006-674), the Centre for Environmental Research in Umeå (CMF) to UB, AA and SL, and by the Swedish strategic research program ECOCHANGE to Umeå University.

Available from: 2015-05-07 Created: 2015-05-05 Last updated: 2015-05-07Bibliographically approved

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