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Biol Open. 2018 Apr 13;7(4). pii: bio030056. doi: 10.1242/bio.030056.

Food supply and size class depending variations in phytodetritus intake in the benthic foraminifer Ammonia tepida.

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Department of Palaeontology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
Department of Palaeontology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
Department of Microbiology and Ecosystem Science, Terrestrial Ecosystem Research, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.


Ammonia tepida is a common and abundant benthic foraminifer in intertidal mudflats. Benthic foraminifera are primary consumers and detritivores and act as key players in sediment nutrient fluxes. In this study, laboratory feeding experiments using isotope-labeled phytodetritus were carried out with A. tepida collected at the German Wadden Sea, to investigate the response of A. tepida to varying food supply. Feeding mode (single pulse, constant feeding; different incubation temperatures) caused strong variations in cytoplasmic carbon and nitrogen cycling, suggesting generalistic adaptations to variations in food availability. To study the influence of intraspecific size to foraminiferal carbon and nitrogen cycling, three size fractions (125-250 µm, 250-355 µm, >355 µm) of A. tepida specimens were separated. Small individuals showed higher weight specific intake for phytodetritus, especially for phytodetrital nitrogen, highlighting that size distribution within foraminiferal populations is relevant to interpret foraminiferal carbon and nitrogen cycling. These results were used to extrapolate the data to natural populations of living A. tepida in sediment cores, demonstrating the impact of high abundances of small individuals on phytodetritus processing and nutrient cycling. It is estimated that at high abundances of individuals in the 125-250 µm size fraction, Ammonia populations can account for more than 11% of phytodetritus processing in intertidal benthic communities.


Carbon and nitrogen intake; Foraminifera; Laboratory feeding experiment; Size specific food intake; Stable isotope labeling

Conflict of interest statement

Competing interestsThe authors declare no competing or financial interests.

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