Published in

Elsevier, Protist, 2(161), p. 288-303, 2010

DOI: 10.1016/j.protis.2009.10.006

Links

Tools

Export citation

Search in Google Scholar

Recycling and Uptake of Si(OH)4 when Protozoan Grazers Feed on Diatoms

This paper is available in a repository.
This paper is available in a repository.

Full text: Download

Green circle
Preprint: archiving allowed
Orange circle
Postprint: archiving restricted
Red circle
Published version: archiving forbidden
Data provided by SHERPA/RoMEO

Abstract

Herbivory of microzooplankton is an emerging key factor of diatom mortality in the ocean. As part of the microbial loop, protozoan grazers also feed on bacteria that accelerate the degradation of diatom detritus. The potentially pivotal effect of microzooplankton grazing on Si(OH)(4) recycling was investigated with cultures of single-celled diatoms, Thalassiosira pseudonana and Chaetoceros gracilis, and heterotrophic protozoans, the dinoflagellate Oxyrrhis marina and the ciliate Strombidium sp. Both grazers ingested diatoms and the bacteria in the non-axenic cultures. C. gracilis, whose frustule is "armed" with setae, was less suitable as a prey than T. pseudonana. Ingestion rates of T. pseudonana were comparable for O. marina and Strombidium, but the dinoflagellate produced two orders of magnitude more detrital bSiO(2) than the ciliate, due to the higher abundance reached by O. marina. Total net release of Si(OH)(4) was lower in the grazing treatments compared to the control possibly due to the reduced bacterial growth by microzooplankton bacterivory, and to the transient protection of detrital bSiO(2) in discarded feeding vacuoles. Over the first 24h, microzooplankton grazing even led to enhanced uptake of Si(OH)(4) by diatoms, confirming the potential of grazing to influence the silicification of diatom frustules. Subsequently however, the Si dynamics in bottles with grazers turned rapidly from net uptake to net Si(OH)(4) release. Protozoan grazers hence tie Si(OH)(4) recycling into the microbial loop by producing detrital bSiO(2).