Termination patterns of Karenia brevis blooms in the eastern Gulf of Mexico

The factors governing the initiation and development of K. brevis blooms in the eastern Gulf
of Mexico are fairly well understood, however the physical, chemical and biological factors
underlying bloom transport and termination are not. The Florida Fish and Wildlife Conservation
Commission’s HAB Monitoring database was analyzed from 1998 - 2021 for temporal trends in
bloom duration, initiation and termination and for repetitive spatial patterns in bloom termination.
A unimodal pattern in bloom initiation was observed, with the most frequent initiations in
September. Bloom termination was more variable, with the most frequent occurrences in April.
Four recurring patterns in bloom termination were identified during this period for southwest
Florida K. brevis blooms: 1) coastal transport south to the Florida Keys then west into the
Gulf of Mexico, 2) transport to the Florida Panhandle with subsequent termination in place,
or 3) via coastal transport west to Alabama, and 4) termination in place in southwest Florida.
These patterns suggest that consistent physical, chemical and biological drivers underlie the
termination stages of K. brevis blooms, and that identification of these drivers may provide
useful management tools for bloom prediction and monitoring.