REMEdiation: Whole lake manipulations to develop REdox and trace MEtal mitigation options for harmful algal blooms (2023-2028)
Despite decades of water quality remediation, cyanobacterial harmful algal blooms (cHABs) and their associated risks remain widespread. Reports of blooms are rising—even in low-nutrient, northern lakes historically considered low-risk—driven by heightened awareness and climate-induced sediment anoxia. Traditional phosphorus-only management targets no longer provide sufficient protection because climate change accelerates oxygen depletion, fundamentally altering internal iron and nitrogen loading dynamics.
Cyanobacteria exhibit uniquely high iron requirements and rely almost exclusively on bioavailable Fe(II). Consequently, iron release from anoxic sediments supplies an essential micronutrient that, when coupled with favourable physical conditions, triggers bloom onset. This biogeochemical framework explains cyanobacterial dominance across diverse systems—from small inland lakes to large transboundary waters, across various trophic states and climate zones. Crucially, it redirects our focus toward management strategies that prevent bloom formation by addressing underlying mechanisms rather than just reacting to symptoms.
Our whole-ecosystem experiments test the core hypothesis that low sediment redox states drive Fe(II) release, which in turn fuels cHABs. Because dissolved oxygen and nitrate act as oxidising agents that suppress iron mobilisation, maintaining sediment redox thresholds offers a clear pathway for managing internal loads. This is an NSERC-funded project.
FORMBLOOM: FORecasting tools and Mitigation options for diverse BLOOM-affected lakes (2017-2023)
formbloom.ca: Freshwater lakes and reservoirs across Canada provide numerous services for local communities, ranging from drinking water to recreation. Unfortunately, these same ecosystems are susceptible to a changing climate and nutrient loading. Cyanobacteria, a common photosynthetic group of microbes in freshwater lakes, are known to grow in excess (or bloom) when nutrient loads are high. Under these conditions, cyanobacteria may have detrimental effects on human, animal, and ecosystem health.
Solving the problem of blooms requires an understanding of how the physical environment links to geochemistry and bloom ecology, and this understanding must exist on the timescale upon which blooms develop and collapse—minutes to hours to weeks. While solving blooms is a grand challenge, managing their impact is a key interim goal. This project is designed to address key environmental factors that drive bloom onset, duration, and cessation while also evaluating the impact blooms have on ecosystem services. This is a GWF-funded project.
Natural Stable Isotopes of Iron: A new tool to trace Fe cycling for management of risk from harmful cyanobacterial blooms in lakes and reservoirs (2016-2020)
Natural stable isotopes of iron contain information about the source of iron required to fuel cyanobacterial blooms. Our recent work has shown the importance of reduced iron to cyanobacteria in embayments along Georgian Bay in support of our conceptual model that links anoxia, phosphorus, nitrogen, iron, and sulphate to cyanobacteria blooms. Following the surprising results in our 2017 paper—which showed intriguing patterns between (a) terrestrial and lake surface waters, (b) dissolved and particulate phases throughout the water column, and (c) the lake surface and bottom—we are employing iron (along with carbon and nitrogen) isotopes to look at the relative importance and timing of Fe sources and processes in Canadian Shield lakes. This is an NSERC-funded project.