Meiofauna in river epilithic biofilm: Dynamics and trophic relationships

Abstract

The long-term dynamics of meiofauna with regards to environmental constraints was monitored in epilithic biofilms of the Garonne River, France. In addition, HPLC-analysis of nematode gut pigment content and a stable isotope multi-approach—including measurement of δ13C and δ15N natural signatures and an in situ 13C-labelling experiment—were performed to disentangle trophic interactions involving biofilm-dwelling meiofauna. Hydrological scenarios and fluctuation of microphyte availability primarily shaped the structure of the meiobenthic community. Also, possible interferences with macro-invertebrate grazers were suspected during July. Chromadorina spp. nematodes grazed non-selectively on epilithic diatom contents, while most of their diet likely derived from extra-cellular polymeric substances produced by microphytes. Freshly photosynthesized carbon was rapidly incorporated by meiofauna, although quantitatively, macrofaunal Chironomidae were the most important grazers.