WAGIS2019

Seagrass communities display complex population patch dynamics at seascape scale that are presently poorly understood as most studies of disturbance on seagrass habitats have focused on changes in biomass at small, quadrat-level scales. In this study, analyses of remote sensing imagery and population modelling were applied to understand seagrass patch dynamics and forecast the fate of these important communities in Biscayne Bay, Miami, Florida, US. We evaluated the historical influence of freshwater deliveries from the Florida Everglades on seagrass communities and documented how changes in salinity can cause seascape fragmentation. Seagrass fragmentation rates were higher in sites adjacent to freshwater canals compared to sites spatially removed from these influences. Furthermore, we documented a clear trend in patch mortality rates with respect to patch size, with the smallest patches undergoing 57% annual mortality on average. The combination of higher fragmentation rates and the higher mortality of smaller seagrass patches in habitats exposed to pulses of low salinity raises concern for the long-term persistence of seagrass meadows in nearshore urban habitats of Biscayne Bay that are presently targets of Everglades restoration. The combined remote sensing and population modelling approach used here provides evaluation and predictive tools that can be used by managers to track seagrass status and stress-response at seascape levels not available previously for the seagrasses of South Florida.