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- Title
Fatty acid profiles and carbon and nitrogen isotopic signature change in Daphnia fed experimental diet consisting of algae and methanotrophic bacteria (MOB).
- Authors
Nykänen, Hannu; Hiltunen, Minna; Kesti, Petri; Syväranta, Jari
- Abstract
Organic matter is transferred across different trophic levels in aquatic systems. Algae andmethanotrophic bacteria can significantly contribute to diets of non-selective filter-feedingzooplankton in aquatic ecosystems. Thus, zooplankton feeding on algae and bacteria formsone biological process that controls the cycling of carbon in aquatic systems. Food quality, interms of fatty acid (FA) content, is an important factor that may govern the efficiency ofcarbon transfer in this crucial trophic step from primary producers to consumers thereforeaffecting also carbon cycling. We studied survival, growth and FA composition of Daphnia magna during a 7-daygrowth experiment. Daphnia were fed with ten algae and MOB mixtures grown indifferent CH4 and CO2 concentrations and temperatures in closed bottles. Stableisotope ratios of C and N were analysed from algae and MOB mixtures and fromDaphnia. Algae and MOB diet did not affect survival of Daphnia. In general, the FA profiles ofDaphnia indicated that they acquired most of their lipids from the algal part of their diet. Incontrast, in the treatment with high share of MOB in the diet, Daphnia accumulated largeamounts of MOB-origin FA, but the Daphnia were small and their total FA content was lowwhen the share of MOB was high. FA composition of Daphnia was not affected by the feedgrowing temperature. Algae and MOB mixture δ13C value range was 7.5 ‰ thus indicating usage of CH4.There was a clear correlation between feed and Daphnia δ13C values, but not between δ13Cvalues of feed and amounts of MOB-origin FAs in Daphnia. Trophic level isotopic enrichment of carbon in Daphnia was clear (1 – 3 ‰).However, δ15N values did not always follow trophic level related isotopic enrichment.
- Subjects
DAPHNIA; METHANOTROPHS; ISOTOPIC signatures; CARBON isotopes; DAPHNIA magna; LEMNA minor; ANIMAL feeds; FRESHWATER algae
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article