Role of bacteria in decomposition of faecal pellets egested by the epiphyte-grazing gastropod Gibbula umbilicaris

Author(s): P. Peduzzi, G. J. Herndl
Abstract: The significance of the microheterotrophic utilization of faecal pellets derived from Gibbula umbilicaris — one of the most important gastropod species in the Posidonia oceanica ecosystem around the Isle of Ischia (Italy) — was investigated by means of microcosm-experiments. Initial total organic carbon (TOC) content of faecal pellets was 32 μgC (mg faeces dry wt)^-1 and declined continuously over a 2-month incubation period. The low values of TOC coincided with SEM observations of pellets which were found to consist mainly of diatom frustules and other slowly utilizable material. In a long-term experiment freshly egested faecal pellets were rapidly colonized by bacteria, which reached densities of up to 14x10⁵ cells (mg faeces dry wt)^-1 within 12 h. Thereafter bacterial numbers declined and fluctuated in a very narrow range between 2 and 3.5x10⁵ cells (mg faeces dry wt)^-1 during the two months of the investigation period. In short-term experiments (over 5 d) similar trends were observed. Peak densities of attached bacteria were followed by a decline of this population. Concurrently the number of free-living bacteria increased. This observation was confirmed by O₂ consumption measurements of freshly egested faecal pellets over 24 h, where the highest O₂ consumption rates were obtained after 12 h, followed by a rapid decline, thus supporting the view that detachment of bacteria may occur. Moreover, the respiration data indicate that about 4% of faecal TOC are remineralized within the first day.
Organisation(s)
Journal: Marine Biology: international journal on life in oceans and coastal waters
Volume: 92
Pages: 417-424
No. of pages: 8
ISSN: 0025-3162
DOI: https://doi.org/10.1007/BF00392682
Publication date: 01-1986
Peer reviewed: Yes
Austrian Fields of Science 2012: 106021 Marine biology
ASJC Scopus subject areas: Ecology, Evolution, Behavior and Systematics, Aquatic Science, Ecology
Sustainable Development Goals: SDG 14 - Life Below Water
Portal url: https://ucrisportal.univie.ac.at/en/publications/role-of-bacteria-in-decomposition-of-faecal-pellets-egested-by-the-epiphytegrazing-gastropod-gibbula-umbilicaris(99869c7e-df02-432e-b90e-cd4a74bb4987).html