Universität zu Köln

von Elert, Eric ORCID: 0000-0001-7758-716X and Fink, Patrick ORCID: 0000-0002-5927-8977 (2018). Global Warming: Testing for Direct and Indirect Effects of Temperature at the Interface of Primary Producers and Herbivores Is Required. Front. Ecol. Evol., 6. LAUSANNE: FRONTIERS MEDIA SA. ISSN 2296-701X

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Abstract

In aquatic food webs, global warming may affect higher trophic levels by increased surface water temperatures and by changing the biochemical composition of phytoplankton. Correlations have suggested that growth of Daphnia, a major consumer of phytoplankton in freshwaters, is limited by a low content of the polyunsaturated fatty acid eicosapentaenoic acid (EPA) in natural phytoplankton and thus by food quality. Here we used the EPA-free green alga Chlamydomonas klinobasis and Daphnia magna to test for such food quality effects. The alga was grown in continuous cultures at 15, 20, and 25 degrees C and, different from other studies, dilution rates accounted for the effects of temperature on algal growth. This resulted in a maximum content of total fatty acids, of total PUFAs, of n-3 PUFAs and of alpha-linolenic acid when grown at 20 degrees C, whereas at 15 degrees C the lowest content of n-6 PUFAs and a threefold higher n-3/n-6 ratio than at 20 and 25 degrees C were observed. Unexpectedly the PUFA content did not show a maximum at 15 degrees C. Growth experiments with D. magna were performed at 15, 20, and 25 degrees C. With C. klinobasis grown at 20 degrees C, Daphnia somatic growth rates increased with temperature. When the alga was raised at the same temperature as Daphnia, somatic growth rates of Daphnia increased with temperature, and supplementation indicated EPA-limitation at 15 degrees C only. At 15 and at 25 degrees C, Daphnia growth was significantly higher on C. klinobasis raised at the respective temperature than on the same alga grown at 20 degrees C. Hence, estimation of temperature effects on Daphnia growth requires to grow the food at the same temperature. At 15 degrees C Daphnia newly built biomass had the highest content in total PUFAs and in a-linolenic acid, whereas the EPA-content was highest at 20 degrees C. The content of n-6 PUFAs increased with temperature, which lead to the highest ratio of n-3/n-6 PUFAs at 15 degrees C. This reflects increased PUFA-assimilation but decreased EPA-synthesis in Daphnia at lower temperatures. The results indicate that only if both algal food and consumer are grown at the same temperature, food quality effects of global warming can be more precisely predicted.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code von Elert, Eric UNSPECIFIED orcid.org/0000-0001-7758-716X UNSPECIFIED Fink, Patrick UNSPECIFIED orcid.org/0000-0002-5927-8977 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-182733
DOI:	10.3389/fevo.2018.00087
Journal or Publication Title:	Front. Ecol. Evol.
Volume:	6
Date:	2018
Publisher:	FRONTIERS MEDIA SA
Place of Publication:	LAUSANNE
ISSN:	2296-701X
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language FATTY-ACID-COMPOSITION; CLIMATE-CHANGE; EICOSAPENTAENOIC ACID; SCENEDESMUS-OBLIQUUS; CHEMICAL-COMPOSITION; DAPHNIA-MAGNA; WATER; ADAPTATION; GROWTH; TERRESTRIAL Multiple languages Ecology Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/18273