Salinity-driven shifts in cyanobacterial toxin concentrations and profiles in prairie lakes

作者：Irena F. Creed, Daniel G. Beach, Kevin J. Erratt, Kelechi Nwokeocha, Lydia Zamlynny, Charles G. Trick · 发表于：Harmful Algae · 年份：2026 · DOI：10.1016/j.hal.2026.103143 · 被引用次数：1 · 研究领域：Aquatic Ecosystems and Phytoplankton Dynamics、Microbial Community Ecology and Physiology、Marine Toxins and Detection Methods

While harmful cyanobacterial blooms are typically linked to nutrient enrichment, the influence of salinity on cyanobacterial toxin occurrence, concentration, and composition across inland waters remains poorly understood. We surveyed >100 Canadian prairie lakes spanning freshwater to hypersaline conditions and quantified cyanobacterial biomass (phycocyanin), community structure (FlowCAM imaging), and congener-resolved toxin profiles (LC-MS/MS). Toxin concentrations varied nonlinearly across the specific conductivity (SpC) gradient, with a first toxin maximum near 1000 µS cm⁻¹ where microcystin concentrations approached ∼400 µg L⁻¹, and a second maximum near 10,000 µS cm⁻¹ where total toxin concentrations approached ∼2000 µg L⁻¹. The lower-SpC maximum coincided with shifts in cyanobacterial community structure and increasing relative abundance of Microcystis near the freshwater-subsaline transition, whereas the upper maximum occurred within the hyposaline range where halotolerant Nodularia emerged and toxin composition shifted from predominantly microcystin profiles toward mixed microcystin + nodularin assemblages. In contrast, cyanobacterial biomass and toxin concentrations declined sharply at higher SpC, and toxins were not detected in mesosaline or hypersaline lakes (> 30,000 µS cm⁻¹). Although nutrients and dissolved organic carbon increased strongly with SpC, toxin concentrations did not track these variables monotonically, indicating that ecological reorganization across...