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Survey of metabolically essential trace metals in inland lakes and reservoirs across Canada: What constitutes a low metal system?
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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.
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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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Data for: Blooms and flows: effects of variable hydrology and management on reservoir water quality
Borealis
Painter, Kristin; Venkiteswaran, Jason; Baulch, Helen M. — 2023-02-10 Flow management has the potential to significantly affect water quality. Shallow lakes in arid regions are especially susceptible to flow management changes which can have important implications for the formation of cyanobacterial blooms. Here, we reveal water quality shifts across a gradient of managed source water inflow regimes. Using in situ monitoring data, we studied a seven-year time span during which inflows to a shallow, eutrophic drinking water reservoir transitioned from primarily natural landscape runoff (2014 to 2015) to managed flows from a larger upstream reservoir (Lake Diefenbaker; 2016 to 2020) and identified significant changes in cyanobacteria (as phycocyanin) using generalized additive models to classify cyanobacterial bloom formation. We then connected changes in water source with shifts in chemistry and the occurrence of cyanobacterial blooms using principal components analysis. Phycocyanin was greater in years with managed reservoir inflow from mesotrophic Lake Diefenbaker (2016 to 2020) but dissolved organic matter (DOM) and specific conductivity, important determinants of drinking water quality, were greatest in years when landscape runoff dominated lake water source (2014 to 2015). Most notably, despite changing rapidly, it took multiple years for lake water to return to a consistent and reduced level of DOM after managed inflows from upstream Lake Diefenbaker were resumed, an observation that underscores how resilience may be hindered by weak resistance to change and slow recovery. Environmental flows for water quality are rarely defined yet here it appears trade-offs exist between poor water quality via elevated conductivity and DOM, and higher bloom risk. Taken together, our findings have important implications for water managers who must protect water quality while adapting to projected hydroclimatic change.
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Data for: Early and late cyanobacterial bloomers in a shallow, eutrophic lake
Borealis
Painter, Kristin; Venkiteswaran, Jason; Simon, Dana F.; Duy, Sung Vo; Sauvé, Sébastien; Baulch, Helen M. — 2022-07-14 This dataset contains data and code for <a href="https://doi.org/10.1002/essoar.10510183.2">"Early and Late Cyanobacterial Bloomers in a Shallow, Eutrophic Lake"</a>, published in <i>Earth and Space Science Open Archive</i>, 2022. Cyanobacterial blooms present challenges for water treatment, especially in regions like the Canadian prairies where poor water quality intensifies water treatment issues. Buoyant cyanobacteria that resist sedimentation present a challenge as water treatment operators attempt to balance pre-treatment and toxic disinfection by-products. Here, we used microscopy to identify and describe the evolution of cyanobacterial species in Buffalo Pound Lake, a key drinking water supply. We used indicator species analysis to identify temporal grouping structures throughout two sampling seasons from May to October 2018 and 2019. Our findings highlight two key cyanobacterial bloom phases – a mid-summer diazotrophic bloom of Dolichospermum spp. and an autumn Planktothrix agardhii bloom. Dolichospermum crassa and Woronchinia compacta served as indicators of the mid-summer and autumn bloom phases, respectively. Different cyanobacterial metabolites were associated with the distinct bloom phases in both years: toxic microcystins were associated with the mid-summer Dolichospermum bloom and some newly monitored cyanopeptides (anabaenopeptin A and B) with the autumn Planktothrix bloom. Despite forming a significant proportion of the autumn phytoplankton biomass (> 60%), the Planktothrix bloom had previously not been detected by sensor or laboratory-derived chlorophyll-a. Our results demonstrate the power of targeted taxonomic identification of key species as a tool for managers of bloom-prone systems. Moreover, we describe an autumn Planktothrix agardhii bloom that has the potential to disrupt water treatment due to its evasion of detection. Our findings highlight the importance of identifying this autumn bloom given the expectation that warmer temperatures and a longer ice-free season will become the norm.

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(source : Wilfrid Laurier University Dataverse) AND (auteur : Baulch, Helen M.)

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