A “black water” event, as observed from satellites, occurred off southwest
Florida in 2012. Satellite observations suggested that the event started in early January and
ended in mid-April 2012. The black water patch formed off central west Florida and
advected southward towards Florida Bay and the Florida Keys with the shelf circulation,
which was confirmed by satellite-tracked surface drifter trajectories. Compared with a
previous black water event in 2002, the 2012 event was weaker in terms of spatial and
temporal coverage. An in situ survey indicated that the 2012 black water patch contained
toxic K. brevis and had relatively low CDOM (colored dissolved organic matter) and
turbidity but high chlorophyll-a concentrations, while salinity was somewhat high
compared with historical values. Further analysis revealed that the 2012 black water was
formed by the K. brevis bloom initiated off central west Florida in late September 2011,
while river runoff, Trichodesmium and possibly submarine groundwater discharge also played important roles in its formation. Black water patches can affect benthic coral reef
communities by decreasing light availability at the bottom, and enhanced nutrient
concentrations from black water patches support massive macroalgae growth that can
overgrow coral reefs. It is thus important to continue the integrated observations where
satellites provide synoptic and repeated observations of such adverse water quality events.