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From adverse to beneficial: Contrasting dietary effects of freshwater mixotrophs on zooplankton

Vad, Csaba Ferenc and Schneider, Claudia and Fischer, Robert and Kainz, Martin J. and Ptacnik, Robert (2021) From adverse to beneficial: Contrasting dietary effects of freshwater mixotrophs on zooplankton. FRESHWATER BIOLOGY, 66 (12). pp. 2272-2282. ISSN 0046-5070

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Abstract

Abstract The importance of mixotrophic algae as key bacterivores in microbial food webs is increasingly acknowledged, but their effects on the next trophic level remain poorly understood. Their high stoichiometric food quality is contrasted by anti-grazing strategies. We tested the quality of freshwater mixotrophs as prey for zooplankton, using four non-colonial chrysophyte species and a cryptophyte as a high quality reference food. We (1) analyzed the stoichiometric and biochemical (fatty acid) composition of the mixotrophs, and (2) quantified their dietary effects on Daphnia longispina survival. Survival of D. longispina significantly depended on the identity of species provided as food, ranging from higher to lower as compared to starvation. This was not reflected in differences in cellular stoichiometry or fatty acid profiles of the mixotrophs. We suggest that toxicity may be the driver for the observed differences. Generalization of the dietary effects of mixotrophic chrysophytes does not appear straightforward. Besides fundamental species-specific differences, potential toxic effects may vary depending on environmental cues or physiological strategies. Notably in our study, Ochromonas tuberculata, a species previously reported to be deleterious, turned out to be a beneficial food source in terms of enabling high survival of D. longispina. We challenge the generality of the assumption that chrysophytes are of low value as food for zooplankton. We recommend that future studies test how environmental conditions and physiological strategies shape the quality of mixotrophs as food for consumers at higher trophic levels, specifically focusing on effects of dietary toxicity.

Item Type: Article
Uncontrolled Keywords: TOXICITY; DAPHNIA; diet quality; chrysophytes; mixotrophic algae;
Subjects: Q Science / természettudomány > QH Natural history / természetrajz > QH540 Ecology / ökológia
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 23 Nov 2021 18:09
Last Modified: 23 Nov 2021 18:09
URI: http://real.mtak.hu/id/eprint/133758

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