Hurricane Irma’s Impact on Water Quality and Phytoplankton Communities in Biscayne Bay (Florida, USA)

The short-term (< 6 months) effects of Hurricane Irma on water quality and phytoplankton community structure were assessed in Biscayne Bay and the adjacent coastal canals from September 2017 through January 2018. The bay experienced sharp fluctuations in daily average salinity and salinity gradients during the passage of the hurricane and significant decreases in salinity as a result of increased freshwater inflows that followed the hurricane (148.2% increase in total inflows in the first week after the hurricane compared to a week before). These decreases were most pronounced in southern and south-central parts of the bay, which experienced the largest post-hurricane increases in freshwater inflows (349.4% and 103.1% in southern and south-central parts of the bay, respectively). Storm-induced increases in inorganic nutrient concentrations stimulated phytoplankton growth in northern, north-central, and southern parts of the bay. Opportunistic phytoplankton taxonomic groups such as chlorophytes and cyanobacteria dominated the total algal biomass pool in the canals, and northern and southern parts of the bay in the weeks following the storm, but they were gradually outcompeted by diatoms in the following months. Changes in spatial-temporal phytoplankton community structure in the months following Hurricane Irma reflect recovery and return to usual seasonal patterns. The effect of Hurricane Irma on water quality and phytoplankton communities was short-lived (< 3 months), suggesting that Biscayne Bay is resilient to tropical cyclones.