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