Response of submerged aquatic vegetation seascapes to a large-scale seagrass die-off: A case study in Florida Bay

Abstract

Heterogeneity across space drives critical ecological processes and understanding the underlying causes of this heterogeneity can provide crucial insight into how resulting patterns may impact these processes. This is especially true in seagrass systems, as they provide ecosystem services such as blue carbon storage, habitat for fish and other fauna, sediment stabilization, and water filtration. However, seagrass ecosystems are threatened worldwide due to coastal water degradation, coastal development, increasing temperatures, and unprecedented marine heat waves. Therefore, it is crucial to understand how disturbances may impact the spatial patterning of seagrass seascapes. Using remote sensing, we investigate how a large-scale seagrass die-off that occurred in Florida Bay during the summer of 2015 and the subsequent recovery impacted the composition and configuration of SAV (submerged aquatic vegetation) seascapes in an area impacted by the die-off (Rankin Basin) and an area that was unaffected (Whipray Basin). The 2015 seagrass die-off decreased the amount of dense SAV across the seascape while leading to a higher density of more complex, smaller patches in Rankin while seascapes in Whipray stayed consistent. During the rapid recovery process in Rankin, patchiness was experienced along the leading edge of the recovering dense SAV, leading to a dynamic seascape that changed location throughout time. Furthermore, it was discovered that each basin exhibited stable and dynamic areas of SAV, with dynamic areas occurring in the shallower regions. This study provides a case study for how SAV seascapes may be impacted (loss of SAV and an increase in fragmentation) by future conditions as marine heat waves and coastal disturbances become more commonplace. However, this study also provides an example of the conditions under which seagrass ecosystems can exhibit resiliency against disturbance, wherein recovery occurred within 2 years of the die-off due to stable conditions and access to genetic material.