Randall W. Parkinson, Levente Juhász , Shimon Wdowinski, Valerie Seidel, Zhaohui Jennifer Fu

The Indian River Lagoon is a 250-km long Estuary of National Significance located along the east central Florida coast of the USA. NOAA tidal records generated at a station located in the central reaches of the estuary indicate sea level rise has accelerated over the past 20 years to an average of 9.6 ± 1.6 mm yr−1 (2003–2022) and it is expected to continue accelerating over the duration of this century. This investigation simulated submergence of the estuary using the on-line geospatial tool Future Shorelines to evaluate the effects of sea level rise on a suite of natural and built attributes that either contribute to or degrade ecosystem services. The simulations are based upon the median NOAA high scenario-based sea level rise trajectory in target years 2050, 2070, and 2100. By 2050, 23% of the public motorized boat ramps and 83% of the spoil islands that provide recreation and conservation services will be inundated. Thirty-three percent of the known or likely septic systems in the study domain will be submerged by 2050. Sea level rise does not reach any of the eleven wastewater treatment plants considered in this study over the next 25 years. Seagrass distribution is expected to decline 32% by 2050 due to a reduction in substate area located above the light-dependent median depth limit. By 2100, all ramps, spoil islands, septic systems, and six wastewater treatment plants will be totally submerged. These findings are conservative because the submergence simulations do not consider (1) the presence of groundwater, (2) that septic systems and the conveyance pipework that deliver wastewater to the treatment facilities are below grade, or (3) stochastic events (e.g., hurricanes).