Cyanobacteria community adaptation in response to diversion operations in coastal Louisiana

Estuaries within the Gulf of Mexico are exhibiting profound alterations due to climatic changes and the implementation of coastal restoration activities. These changes are attributed to the increasing frequency of cyanoHABs within Lake Pontchartrain, an estuary located in southeastern Louisiana. Many cubic km of nutrient rich freshwater from the Mississippi River are diverted into Lake Pontchartrain via the opening of the Bonnet Carré Spillway (BCS). In 2019, the region saw two openings of the spillway for the longest duration on record with a total of 123 days. As a result, a massive cyanoHAB was documented across the estuary. In 2021, the BCS remained closed but there continued to be localized blooms of cyanobacteria indicating alternative sources that may fuel the growth of cyanoHABs. To determine the effects of the timing and duration of the BCS openings on cyanoHAB prevalence and toxicity, data on water quality, phytoplankton community composition, and toxin production was collected throughout 2019 and 2021. By understanding the effects of nutrient loading and physical dynamics on cyanoHAB formation and proliferation, we can more accurately predict the future impacts of the BCS and other freshwater sources on the Louisiana coastal health