Cnudde, C. (2007). Mariene coprofagie: belang van fecale pellets voor de voedselopname van Paramphiascella fulvofasciata (Copepoda, Harpacticoida). [Marine coprophagy: importance of fecal pellets for the feeding of Paramphiascella fulvofasciata (Copepoda, Harpacticoida).]. MSc Thesis. Universiteit Gent. Faculteit Wetenschappen. Vakgroep Biologie: Belgium. 108 pp. [In Flemish.].
71239
Cnudde, C.
2007
Mariene coprofagie: belang van fecale pellets voor de voedselopname van Paramphiascella fulvofasciata (Copepoda, Harpacticoida). [Marine coprophagy: importance of fecal pellets for the feeding of Paramphiascella fulvofasciata (Copepoda, Harpacticoida).]
Benthic meiofauna plays an important quantitative role in marine food webs. There is a growing interest to explore and know more about the interactions in aquatic food webs. In marine sediments harpacticoid copepods (Crustacea, Copepoda) are typically the second most abundant meiofauna taxa. From a functional point of view they form a crucial and complex link between primary producers and higher trophic levels. As consumers of microalgae and micro-organisms they are responsible for a (direct) transfer of primary production. But also indirect, through uptake of micro-organisms on faecal material or faecal pellets as such, primary production is transferred to higher organisms. Harpacticoids are selective feeders of amongst others diatoms, bacteria and detrital matter. Despite of this food selectivity they are able to switch between food sources, reflecting a feeding strategy that increases their chances in conditions of food limitation and interference competition. The switch to bacterivorous feeding seems possible but the existence of preferential bacterivorous feeding of benthic copepods is less largely unknown, in contrast to what is known from pelagic species (e.g. Oithona sp.).
In this thesis, the role of faecal pellets for the feeding ecology of Paramphiascella fulvofasciata was studied. The central hypothesis is that this harpacticoid species is feeding on micro-organisms that can be found in association with faecal pellets. It was tested whether bacterivory was related to the type of available food source. In this study the diatom species Seminavis robusta en Navicula phyllepta were used as main food source. In addition, possible differences between micro-organisms associated with species-own and allochtonous faecal pellets were tested. It was questioned whether a bacteria-specific feeding behaviour of P. fulvofasciata could be found.
A grazing experiment with 13C enriched diatoms and additional faecal pellets showed that the presence of faecal pellets caused an increased BC enrichment of the grazer P. fulvofasciata although this effect was not found significantly.
A detailed study of the growth of the diatom species N. phyllepta proved that bacterivory by P. fulvofasciata should not excluded although an important amount of this diatom species was grazed upon. A comparable study on the diatom species S. robusta showed a low level of diatom grazing. This outcome supports a preferential bacterivory by P. .fulvofascoata. Apart from grazing effects on the diatom density, it was also found that the initial absence of faecal matter promoted the production of more but smaller faecal pellets. These results indicate the importance and the need of a bacterial enriched environment for P. fulvofasciata.
A final grazing experiment using N. phyllepta as main food sources and additional allochtonous faecal pellets learned that allochtonous pellets had no effect on the food uptake by P. fulvofasciata.
Finally, it is possible that the age of faecal pellets plays an important role. Older and partly defragmented pellets are karakterised by a different bacterial community than freshly produced pellets.
A second part of this thesis aimed at characterising the micro-organisms in the different feeding experiments. Isolates were collected from species-own faecal pellets, allochtonous faecal pellets, fresh and older faecal pellet and from 2 diatom species. By means of (gtg)5analysis, FAME-analysis and partial 16S rRNA gen sequencing 8 genera were identified. The genera Roseobacter, Flavobacterium, Pseudomonas, Sulfitobacter, Bacillus, Alteromonas, Pseudoalteromonas sp., Marinobacter sp. were found to be associated with faecal pellets of different origin. The 3 latter genera were also found in association with the diatom species S. robusta and N. phyllepta. From a feeding ecological point of view, it can be concluded that the transit through the digestive track of the harpacticoid copepod causes an important change in the community composition of the food associated micro-organisms. In this way, the production of faecal pellets guarantees an enrichment of micro-organisms in the environment.
