What the study covers
This urban pond harmful algal bloom study tracked five retention ponds in Northern Kentucky for a full year and measured both cyanobacterial cell counts and microcystin toxin levels. Researchers from the U.S. EPA and Northern Kentucky University found that 75 % of samples exceeded WHO’s 20,000 cells mL-1 HAB threshold while 66 % topped the 4 ppb microcystin health limit. Yet toxin spikes didn’t always match high Microcystis counts, challenging the “cells = toxins” rule of thumb.
Key findings
- HABs occurred year-round—even at 3 °C in January.
- Microcystin hit 1,286 ppb during the coldest sample event.
- No single water-quality factor (pH, DO, nutrients) predicted bloom toxicity.
- Ponds with vegetated buffer zones recorded milder blooms.
Why it matters for East & Middle TN managers
Small HOA and storm-water ponds in Tennessee share the same shallow, nutrient-rich profile as the Kentucky sites. This urban pond harmful algal bloom study shows why January can be just as risky as July—and why monitoring must track toxins, not just cells.
Download the full PDF to see the data tables, WHO comparisons, and practical design tweaks (buffer width, aeration) that cut bloom severity.
