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Volume 7, issue 8
Biogeosciences, 7, 2419–2432, 2010
https://doi.org/10.5194/bg-7-2419-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 7, 2419–2432, 2010
https://doi.org/10.5194/bg-7-2419-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  16 Aug 2010

16 Aug 2010

The trophic biology of the holothurian Molpadia musculus: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon

T. Amaro1,3, S. Bianchelli2, D. S. M. Billett3, M. R. Cunha1, A. Pusceddu2, and R. Danovaro2 T. Amaro et al.
  • 1CESAM e Departamento de Biologia, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
  • 2Dipartimento di Scienze del Mare,Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
  • 3National Oceanography Centre, Southampton University of Southampton, Waterfront Campus, European Way Southampton SO14 3ZH, UK

Abstract. Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m−2 d−1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.

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