Gabor, Rachel S 1 ; Gillis, Carole-Anne 2 ; Cullis, James D 3 ; Bothwell, Max L 4
1 University of Colorado Boulder
2 Centre Eau Terre Environnement, Quebec, Canada
3 University of Colorado Boulder
4 Environment Canada
The first official observation of Didymosphenia geminata (didymo), an invasive diatom, in Eastern Quebec occurred in the Matapedia River in July 2006. This Atlantic salmon fishing river has several characteristics shown to favor didymo's ability to form thick, extensive benthic mats, including stable flow and oligotrophic nutrient conditions. Since the incursion, rapid colonization and inter-catchment transfer processes were observed, notably in surrounding watersheds on the Gaspé Peninsula as well as in northern New Brunswick. All affected watersheds share favorable characteristics for didymo growth, including high light, low nutrient waters, and stable substrate. The nearby North Shore of the St. Lawrence, which also contains rivers with conditions that would favor didymo growth, has not yet shown didymo presence. This natural system provides a comparison to identify necessary parameters for didymo growth, with differences primarily due to geology-driven water chemistry. Pre-incursion water chemistry was compared between the two regions. Rivers in the region where didymo is present displayed a high alkalinity and corresponding higher pH, due to increased concentrations of magnesium and calcium, than rivers in regions where didymo has not appeared. Also, rivers with didymo showed a lower amount of color-causing compounds, such as organic carbon, and clearer water, which supports the theory that high light levels encourage didymo growth.
Kumar, S., S. A. Spaulding, T. J. Stohlgren, K. A. Hermann, T. S. Schmidt, and L. L. Bahls, 2009, Potential habitat distribution for the freshwater diatom Didymosphenia geminata in the continental US, Front. Ecol. Environ., 7(8), 415-420.
MDDEP, 2008. What is Didymo and How Can We Prevent It From Spreading In Our Rivers? Ministère du Développement durable, de l'Environnement et des Parcs, Direction du suivi de l'état de l'environnement, 13 p. 3rd Edition Legal deposit: Bibliothèque et archives nationales du Québec, 2008 ISBN: 978-2-550-52758-9 (PDF)