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Survey of metabolically essential trace metals in inland lakes and reservoirs across Canada: What constitutes a low metal system?
Borealis
Molot, Lewis A.; Schiff, Sherry; Baulch, Helen M.; Curry, R.Allen; Depew, David C.; Dove, Alice; Higgins, Scott N.; Kidd, Karen A.; Korosi, Jennifer B.; Paterson, Andrew M.; Pick, Frances R.; Venkiteswaran, Jason; Watson, Susan B.; Zastepa, Arthur — 2024-09-16 Trace metals are metabolically essential with many proteins dependent on metals for proper functioning yet little is known about the influence of low concentrations on freshwater microbial productivity and diversity. Dissolved iron (Fe), manganese (Mn), zinc (Zn), molybdenum (Mo), nickel (Ni), cobalt (Co), copper (Cu) and vanadium (V) were surveyed in 39 lakes and reservoirs across Canada representing different geology, dominant land uses, lake depth, trophic status and climatic zones. Concentrations varied considerably and cross-Canada patterns were not uniform among the eight metals, but PCA analysis revealed two major patterns: Co, Cu, Ni and V in one group and Fe and Mn in a second group. Sub-nanomolar concentrations of Co and Mo were common while sub-nanomolar concentrations of Zn, V and Ni were less common. Fe and Mn accumulated in the hypolimnion of the six lakes and reservoirs deep enough to thermally stratify with Co and Zn accumulation less common. Mo, Zn and Fe occasionally exceeded Canadian guidelines for protection of aquatic biota. Genomics and Monod growth kinetics were explored for their potential in identifying low metal environments and metal limitation without using metal enrichment bioassays. Metal concentrations in the cross-Canada survey were probably not low enough to limit growth but the impact of low metals on microbial diversity is unknown.
Wilfrid Laurier University Dataverse Translation missing: fr.blacklight.search.logo
Phosphorus-only fertilization rapidly initiates large nitrogen-fixing cyanobacteria blooms in two oligotrophic lakes
Borealis
Molot, Lewis A.; Higgins, Scott N.; Schiff, Sherry; Venkiteswaran, Jason; Paterson, Michael J.; Baulch, Helen M. — 2021-06-15 Two small, oligotrophic lakes at the IISD-Experimental Lakes Area in northwestern Ontario, Canada were fertilized weekly with only phosphorus (P) in the summer and early fall of 2019. The P fertilization rates were high enough (13.3 µg L-1 added weekly) to produce dense, month-long blooms of N2-fixing Dolichospermum species in both lakes within 9-12 weeks after fertilization began, turning them visibly green without the addition of nitrogen. P-only fertilization increased average seasonal chlorophyll a concentrations and cyanobacteria biomass well above the pre-fertilization levels of 2017 and 2018. Nitrogen (N) content in the epilimnion of thermally stratified Lake 304 and the water column of shallow Lake 303 doubled and P storage in the water column temporarily increased during the blooms. These whole-lake fertilization experiments demonstrate that large cyanobacteria blooms can develop rapidly under high P loading without anthropogenic N inputs, suggesting that aggressive N control programs are unlikely to prevent bloom formation and that P controls should remain the cornerstone for cyanobacteria management.

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(auteur : Higgins, Scott N.)

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