A Population-Based Approach to Restore and Manage Ruppia Maritima (Wigeongrass) in the Highly Variable Everglades-Florida Bay Ecotone

Seagrasses and submerged aquatic vegetation (SAV) continue to decline globally from human-induced disturbance and habitat loss in estuarine and coastal ecosystems. The SAV Ruppia maritima historically created critical habitat at the Everglades-Florida Bay ecotone, but hydrological modifications and lower freshwater flows have resulted in significant declines in recent decades. We used a population-based approach to examine factors controlling Ruppia presence and abundance at the ecotone to expand the scientific base for management and restoration of SAV species in highly variable environments and examine factors required for Ruppia restoration in the Everglades. Life history transitions from seed through sexual reproduction were established under a range of field conditions critical to seagrass and SAV persistence, including salinity, temperature, light, sediment nutrients (P) and competitor SAV. We found multiple constraints to Ruppia life history development, including an ephemeral seed bank, low rates of successful germination and seedling survival and clonal reproduction limited by variable salinity, nutrients, light and competition with the macroalga Chara hornemannii. Because of low survival rates and limited clonal reproduction, Ruppia at the Evergaldes ecotone currently depends on high rates of viable seed production. However, development of large reproductive meadows requires high vegetative shoot densities. Thus, Everglades restoration should establish lower salinities to create higher seedling and adult survival and clonal reproduction to support successful sexual reproduction that can build up the seed bank for years when adult survival is limited. This population-based data from field experiments and surveys is being incorporated into a seagrass model to enable forecasting of population sustainability and evaluate Everglades restoration targets which includes restoring Ruppia to the southern Everglades-Florida Bay ecotone.