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Bacterivory in the common foraminiferAmmonia tepida: Isotope tracer experiment and the controlling factors

Authors
Journal
Journal of Experimental Marine Biology and Ecology
0022-0981
Publisher
Elsevier
Publication Date
Volume
359
Issue
1
Identifiers
DOI: 10.1016/j.jembe.2008.02.018
Keywords
  • Bacteria
  • Environmental Factor
  • Foraminifera
  • Grazing
  • Mudflat
  • Prey Abundance
  • Trophoecology
Disciplines
  • Ecology
  • Geography

Abstract

Abstract The majority of sediment dweller foraminifera are deposit feeders. They use their pseudopodia to gather sediment with associated algae, organic detritus and bacteria. Uptake of bacteria by foraminifera have been observed but rarely quantified. We measured uptake of bacteria by the common foraminifera Ammonia tepida using 15N pre-enriched bacteria as tracers. In intertidal flats, seasonal, tidal and circadian cycles induce strong variations in environmental parameters. Grazing experiments were performed in order to measure effects of abiotic (temperature, salinity and irradiance) and biotic (bacterial and algal abundances) factors on uptake rates of bacteria. In mean conditions, A. tepida grazed 78 pgC ind − 1 h − 1 during the first eight hours of incubation, after which this uptake rate decreased. Uptake of bacteria was optimal at 30 °C, decreased with salinity and was unaffected by light. Above 7 × 10 8 bacteria ml wt sed − 1 , uptake of bacteria remained unchanged when bacterial abundance increased. Algal abundance strongly affected algal uptake but did not affect uptake of bacteria. As uptake of bacteria represented 8 to 19% of microbes (algae plus bacteria) uptake, Ammonia seemed to be mainly dependant on algal resource.

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