Bibliothèque Électronique Lac Saint-Pierre

Shift from chlorophytes to cyanobacteria in benthic macroalgae along a gradient of nitrate depletion

Vis, C. et Cattaneo, A. et Hudon, C. (2008). Shift from chlorophytes to cyanobacteria in benthic macroalgae along a gradient of nitrate depletion. Journal of Phycology , 44 (1). p. 38-44. DOI: DOI: 10.1111/j.1529-8817.2007.00429.x.

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A survey of the spatial distribution of benthic macroalgae in a fluvial lake of the St. Lawrence River (Lake Saint-Pierre, Quebec, Canada) revealed a shift in composition from chlorophytes to cyanobacteria along the flow path of nutrient-rich waters originating from tributaries draining farmlands. The link between this shift and changes in water quality characteristics was investigated by sampling at 10 sites along a 15 km transect. Conductivity, current, light extinction, total phosphorus (TP; >25 µg P ·L-1 ), and ammonium (8–21 µg N ·L-1 ) remained fairly constant along the transect in contrast to nitrate concentrations, which fell sharply. Filamentous and colonial chlorophytes [Cladophora sp. and Hydrodictyon reticulatum (L.) Bory] dominated in the first 5 km where nitrate concentrations were >240 µg N ·L-1 . A mixed assemblage of chlorophytes and cyanobacteria characterized a 1 km transition zone where nitrate decreased to 40–80 µg N ·L-1. In the last section of the transect, nitrate concentrations dropped below 10 µg N ·L-1, and cyanobacteria (benthic filamentous mats of Lyngbya wollei Farl. ex Gomont and epiphytic colonies of Gloeotrichia) dominated the benthic community. The predominance of nitrogen- fixing, potentially toxic cyanobacteria likely resulted from excessive nutrient loads and may affect nutrient and trophic dynamics in the river.

Type de document: Article scientifique
Statut du texte intégral: Autre
Mots-clés libres: Benthic algae, Cyanobacteria, Lyngbya, Macroalgae, Nitrogen, River
Sujets: 3. Végétation, milieux humides
8. Impacts et monitoring > 8.1. Qualité de l’eau
Date de dépôt: 25 août 2016 14:49
Dernière modification: 25 août 2016 14:49

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