1. Long-term changes in nutrient dynamics and plankton communities following the creation of a new reservoir
- Author
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Paterson, Michael J., Beaty, Kenneth G., Findlay, David L., Findlay, Willie J., Schiff, Sherry L., St.Louis, Vincent L., and Venkiteswaran, Jason J.
- Subjects
Earth sciences - Abstract
Reservoir creation often leads to a 'trophic upsurge' of nutrients that may affect communities living near impoundments. We determined the duration of the nutrient upsurge and associated changes in plankton in a study of a new reservoir (Lake 979; L979) in northwestern Ontario that included 2 years pre-impoundment, 16 years of impoundment, and 2 years postimpoundment. Secondarily, we determined allochthonous versus autochthonous carbon (C) use by zooplankton with reservoir development. For the first 6-14 years of impoundment, mean concentrations of total phosphorus (TP), total nitrogen (TN), and dissolved organic carbon increased 3.6, 2.4, and 1.7 times above pre-impoundment levels, respectively, decreasing thereafter. L979 shifted from a net sink to a source of TP and TN for the first 6 years of impoundment. Mean annual biomasses of bacteria, phytoplankton, and zooplankton increased 4.6,17, and 32.6 times above pre-impoundment levels, respectively, with associated changes in community composition. Bacteria and phytoplankton returned to pre-impoundment levels within 4 and 10 years, respectively, but zooplankton densities remained elevated even after 18 years. Changes in [[delta].sup.13]C suggested that postim poundment zooplankton biomass was not supported predominantly by allochthonous C. La creation d'un reservoir entraine souvent une<< flambee trophique >>de nutriments qui peut avoir une incidence sur les communautes vivant pres des ouvrages de retenue. Nous avons determine la duree de la flambee de nutriments et de changements associes dans le plancton dans le cadre de l'etude d'un nouveau reservoir (lac 979; L979) dans le Nord-Ouest de l'Ontario, portant sur 2 annees avant, 16 annees durant, et 2 annees apres la retenue des eaux. En deuxieme lieu, nous avons determine l'utilisation de carbone (C) allochtone et autochtone par le zooplancton selon l'etat du reservoir. Pour les 6 a 14 premieres annees de retenue, les concentrations moyennes de phosphore total (TP), d'azote total (TN), et de carbone organique dissous sont passees, respectivement, a 3,6,2,4, et 1,7 fois les concentrations pre-retenue, pour diminuer par la suite. De puits net, le reservoir L979 est devenu une source en ce qui concerne le TP et le TN pour les 6 premieres annees de retenue. Les biomasses annuelles moyennes de bacteries, de phytoplancton, et de zooplancton sont passees, respectivement, a 4,6,17, et 32,6 fois les valeurs pre-retenue, avec les modifications en decoulant a la composition des communautes. Les bacteries et le phytoplancton etaient retournes a leurs niveaux pre-retenue apres 4 et 10 ans, respectivement, mais les densites de zooplancton demeuraient elevees apres 18 ans. Les modifications du [[delta].sup.13]C donnent a penser que la biomasse de zooplancton apres la retenue n'etait pas supportee principalement par du C allochtone. [Traduit par la Redaction], Introduction Many water bodies have been affected by the construction of dams and reservoirs for hydropower generation, flood protection, irrigation, water supply, and recreation. Globally, there are over 56 000 [...]
- Published
- 2019
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