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Changes in the pelagic microbial food web due to artificial eutrophication
Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
2006 (English)In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, Vol. 40, no 3, 299-313 p.Article in journal (Refereed) PublishedText
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.

Place, publisher, year, edition, pages
Umea Univ, Dept Ecol & Environn Sci, Marine Ecol, SE-90187 Umea, Sweden. Umea Marine Sci Ctr, SE-91020 Hornefors, Sweden. Linkoping Univ, Dept Mol & Clin Med, Div Med Microbiol, SE-58185 Linkoping, Sweden. Univ Copenhagen, Bot Inst, DK-1353 Copenhagen K, Denmark., 2006. Vol. 40, no 3, 299-313 p.
Keyword [en]
bacteria, food web structure, mesocosm experiments, mesozooplankton, phytoplankton, protozoa
National Category
Research subject
biology, Environmental Science
URN: urn:nbn:se:umu:diva-112584DOI: 10.1007/s10452-006-9041-7ISI: 000240724100002OAI: diva2:881473
Available from: 2015-12-10 Created: 2015-12-10 Last updated: 2015-12-10

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Albertsson, Jan
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Umeå Marine Sciences Centre (UMF)
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