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Changes in the pelagic microbial food web due to artificial eutrophication
Marine Ecology, Department of Ecology and Environmental Science, Umeå University, SE-901 87 Umeå, Sweden, Umeå Marine Sciences Centre, SE-910 20 Hörnefors, Sweden.
Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Medical Microbiology .
Umeå Marine Sciences Centre, SE-910 20 Hörnefors, Sweden, Botanical Institute, University of Copenhagen, Oster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark.
Umeå Marine Sciences Centre, SE-910 20 Hörnefors, Sweden.
2006 (English)In: Aquatic Ecology, ISSN 1386-2588, Vol. 40, no 3, 299-313 p.Article in journal (Refereed) Published
Abstract [en]

The effect of nutrient enrichment on the structure and carbon flow in the pelagic microbial food web was studied in mesocosm experiments using seawater from the northern Baltic Sea. The experiments included food webs of at least four trophic levels, (1) phytoplankton-bacteria, (2) flagellates, (3) ciliates and (4) mesozooplankton. In the enriched treatments high autotrophic growth rates were observed, followed by increased heterotrophic production. The largest growth increase was due to heterotrophic bacteria, indicating that the heterotrophic microbial food web was promoted. This was further supported by increased growth of heterotrophic flagellates and ciliates in the high nutrient treatments. The phytoplankton peak in the middle of the experiments was mainly due to an autotrophic nanoflagellate, Pyramimonas sp. At the end of the experiment, the proportion of heterotrophic organisms was higher in the nutrient enriched than in the nutrient-poor treatment, indicating increased predation control of primary producers. The proportion of potentially mixotrophic plankton, prymnesiophyceans, chrysophyceans and dinophyceans, were significantly higher in the nutrient-poor treatment. Furthermore, the results indicated that the food web efficiency, defined as mesozooplankton production per basal production (primary production + bacterial production - sedimentation), decreased with increasing nutrient status, possibly due to increasing loss processes in the food web. This could be explained by promotion of the heterotrophic microbial food web, causing more trophic levels and respiration steps in the food web. © Springer Science+Business Media B.V. 2006.

Place, publisher, year, edition, pages
2006. Vol. 40, no 3, 299-313 p.
Keyword [en]
Bacteria, Food web structure, Mesocosm experiments, Mesozooplankton, Phytoplankton, Protozoa
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-50127DOI: 10.1007/s10452-006-9041-7OAI: diva2:271023
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2011-01-11

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