After the crash of an algae bloom
Some ponds have very dense algae blooms dominated by one or two species.
For reasons that are not well understood, these blooms are subject to spectacular collapse,
often called a “crash,” where all the algae suddenly die. When this occurs, ammonia concentration
increases rapidly because the main mechanism for ammonia removal—algal uptake—has been eliminated.
Rapid decomposition of dead algae reduces the dissolved oxygen concentration and pH and increases ammonia and carbon dioxide concentrations.
After the crash of an algae bloom, ammonia concentration can increase to 6 to 8 mg/L and the pH can decline to 7.8 to 8.0. The 4-day chronic criterion, the appropriate criterion to apply