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Abstract
In June 2006, blooms of Didymosphenia geminata (Lyngbye) M. Schmidt were observed for the first time in the Matapedia River, Quebec. This species can produce nuisance-level epilithic algal mats in oligotrophic rivers with stable flows. The lack of knowledge surrounding the potential impacts of nuisance growths on lotic ecosystems has raised concerns. Periphyton communities were sampled in three rivers of the Restigouche watershed to assess the effects of D. geminata nuisance growths on surrounding diatom assemblages. This study provides a preliminary assessment of the effect of D. geminata on the species composition of diatom assemblages and the influence of increased biofilm complexity on species diversity. Our results show that D. geminata mats have an effect on the structure and diversity of diatom assemblages. Conversely, we found no evidence that an increase in Standing Crop Index (SCI) further impacted diatom diversity or structure of these assemblages. This preliminary study contributes to the growing knowledge of the biology and impact of D. geminata in lotic environments.
Acknowledgements
This is a contribution from the Groupe de recherche interuniversitaire en limnologie et en environnement aquatique. Carole-Anne Gillis was funded by NSERC-FQRNT BMP-Innovation grant through collaboration and support by the Matapedia-Restigouche Watershed Organization. Many thanks to Normand Bergeron and the Corporation de Gestion des Rivieres Matapedia et Patapedia (CGRMP) for enabling this research effort. The Didymo Volunteer Network was of support in determining sampling site location. Thank you to Anne Provencher St-Pierre, Magaly Oakes and Rebecca Gagnon for their field assistance and to Cedric Sirois for mapping.