Human activity in fishponds leads to explosive growth of harmful algae.
Phytoplankton in fishponds is affected by human activity. The study looked at phytoplankton in fishponds and nearby rivers over a growing season. Phytoplankton biomass peaks in spring and autumn in fishponds, while the nursery pond has one long peak. Fishponds have 6.2–10.1 times more phytoplankton than rivers. Cyanobacteria and Chlorophyta are common in fishponds but rare in rivers.