Impacts of biogenic structures on benthic assemblages: microbes, meiofauna, macrofauna and related ecosystem functions

• DOI: 10.3354/meps09915
• Publication Date: 2012-07-26T10:59:37Z
• Authors: C Passarelli; F Olivier; DM Paterson; C Hubas
• Keywords: [SDE] Environmental Sciences; 0106 biological sciences; 570; Biofilm; Meiofauna; Sediment stability; Microphytobenthos; 15. Life on land; 01 natural sciences; Polychaete tubes; Biogenic structures; 13. Climate action; [SDE]Environmental Sciences; Macrofauna; 14. Life underwater; Carbon flux

Species that modify their surroundings are known as ecosystem engineers. For example, patches of polychaete tubes enhance soft-bottom intertidal habitat complexity, modify- ing water flow, promoting sediment accretion and affecting nutrient fluxes at the water-sediment interface. Understanding how such structures affect the benthic ecosystem's functioning requires the assessment of their influence on all benthic components and how the related ecosystem serv- ices may be modified. We performed an in situ experimental study, involving the use of artificial mimics of polychaete tubes, to investigate the purely physical impacts of the structures without the complexity of worm activity. Benthic chambers of different mimic densities were used, and their effect on the recolonisation of defaunated natural sandy sediments by microorganisms, meio- fauna and macrofauna was monitored. We also measured air-sediment CO2 fluxes and sediment stability as they constitute crucial ecosystem services provided by benthic habitats. We showed that the biogenic structures stimulated the development of diatom biofilms (microphytobenthos) and their associated extracellular polymeric substances (EPS). Impacts of tubes on meiofaunal and macrofaunal assemblages were significant; in most cases, species and groups were more abun- dant in treatments with few or no tubes. In response to the tube density increase, the whole system tended towards heterotrophy and higher sediment stability, probably as a consequence of the development of the diatom biofilm. Biogenic structures are, therefore, of critical importance for soft-bottom intertidal communities in terms of both structure and function.