Increased production of faecal pellets by the benthic harpacticoid Paramphiascella fulvofasciata: importance of the food source
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The re-use of faecal pellets in the water column before sinking to the seafloor is known as an important pathway in marine food webs. Especially planktonic copepods seems to be actively use their faecal pellets. Since benthic copepods (order Harpacticoida) live in the vicinity of their pellets, it remains unclear how important these pellets are for their feeding ecology. In the present study a laboratory experiment was conducted to analyse the importance of faecal pellets for the feeding ecology of the harpacticoid Paramphiascella fulvofasciata and its grazing pressure on two diatom species (Seminavis robusta, Navicula phyllepta). By quantifying the amount and volume of the produced faecel pellets in different treatments, it was tested to what extent the food source and the lack of faecal pellets would influence the production of faecal pellets. We found that the grazing pressure of P. fulvofasciata depended on the diatom density since only a top-down effect could be found on the smaller Navicula cells during its initial exponential growth phase. The grazer had a negative effect on the diatom growth and controlled the cell density to about 4,000 cells/cm2. In spite of the fact that the addition of faecal pellets did not show a significant positive effect on the assimilation of diatoms, the removal of faecal pellets strongly promoted the pellet production. Especially when grazing on Navicula the harpacticoid P. fulvofasciata produced significantly more and smaller faecal pellets when the pellets were removed. This outcome illustrates the need for faecal pellets of this harpacticoid copepod when grazing on the diatom Navicula. Apart from its selection for smaller diatom cells, it was suggested that the colonisation of heterotrophic bacteria enriched these pellets. This study is the first to indicate that trophic upgrading occurs on faecal pellets and not only on the initial autotrophic food sources per se.
KeywordsFaecal Pellet Navicula Harpacticoid Copepod Diatom Cell Planktonic Copepod
M. de Troch is a Postdoctoral Fellow of the Research Foundation - Flanders (FWO). This study was conducted within the frame of FWO research project G.0313.04. Additional support was provided by the Ghent University (BOF-GOA 01GZ0705). The authors acknowledge the support by the MarBEF Network of Excellence ‘Marine Biodiversity and Ecosystem Functioning’ which is funded by the Sustainable Development, Global Change and Ecosystems Programme of the European Community’s Sixth Framework Programme (contract no. GOCE-CT-2003-505446). This publication is contribution MPS-08049 of MarBEF. Two anonymous referees provided valuable remarks in order to improve an earlier version of this paper.
- Bec A, Martin-Creuzburg D, von Elert E (2006) Trophic upgrading of autotrophic picoplankton by the heterotrophic nanoflagellate Paraphysomonas sp. Limnol Oceanogr 51:1699–1707Google Scholar
- Cowey CB, Corner ED (1966) The amino acid composition of certain unicellular algae, and of the fecal pellets produced by Calanus jinmurchicus when feeding on them. In: Barnes H (ed) Some contemporary studies in marine science. Allen and Unwin, London, pp 225–231Google Scholar
- Guillard RL (1975) Culture of phytoplankton for feeding marine invertebrates. In: Smith WL, Chandley MH (eds) Culture of marine invertebrate animals. Plenum Press, New York, pp 26–60Google Scholar
- Hutchins DA, Wang WX, Fisher NS (1995) Copepod grazing and the biogeochemical fate of diatom iron. Limnol Oceanogr 40:989–994Google Scholar
- Mourelatos S, Rougier C, Lacroix G (1992) Radiotracer losses due to freezing in formalin of carbon-14-labeled cladocerans. Arch Hydrobiol 126:239–253Google Scholar
- Viitasalo M, Rosenberg M, Heiskanen AS, Koski M (1999) Sedimentation of copepod fecal material in the coastal northern Balthic Sea: where did all the pellets go? Limnol Oceanogr 44:1388–1399Google Scholar
- Wexels Riser C, Reigstad M, Wassmann P, Arashkevich E, Falk-Petersen S (2007) Export or retention? Copepod abundance, faecal pellet production and vertical flux in the marginal ice zone through snap shots from the northern Barents Sea. Polar Biol 30:719–730. doi: 10.1007/s00300-006-0229-z CrossRefGoogle Scholar
- Wotton RS (2001) Life in water. An internet book. Chapter 5: Trophic status, food availability and feeding by aquatic animals. http://www.ucl.ac.uk/~ucbt212/