Trophic interactions within the kelp holdfast communities in the Beagle Channel: a biomarker approach

Stephanie Roy

Kelp forests from Southern Argentina are pristine ecosystems, but increasing anthropogenic activities have been threatening them with higher levels of pollution. A shift in the food web structure caused by this stressor could largely affect economically important species, such as the southern king crab (Lithodes santolla). Characterised as efficient trophic biomarkers, fatty acids (FA) are a good tool to study the effect of pollution and the trophic interactions in the benthic food web. This study focuses on the effect of pollution on macroinvertebrates and primary producers associated with dead and alive holdfasts in the Macrocystis pyrifera dominated forest of Tierra del Fuego, Argentina. The community composition differed between sites and holdfast states. The polluted site contained more suspension feeders than the pristine site. The dead holdfast hosted more species than the alive one. The FA composition, examined only in the pristine site, was not different between the dead and alive holdfast communities. The FA composition was very species-specific. Overall, the holdfast state was a minor factor influencing macroinvertebrates compared to the effect of the local site characteristics. FA comparison with the polluted site is required to better understand the impact of pollution on trophic relationships in the holdfast community.