Ruppia maritima L. seed bank viability at the Everglades-Florida Bay ecotone

Abstract

Ruppia maritima L. is a cosmopolitan habitat-forming seagrass species that historically dominated at the Everglades-Florida Bay ecotone in the Greater Everglades Ecosystem. Currently, however, this species exhibits a patchy and ephemeral distribution which results in a degraded habitat. Thus, an important goal in Everglades’ habitat restoration is to increase R. maritima abundance in the southern Everglades estuaries. We tested the hypothesis that a lack of seed bank viability may be limiting R. maritima recruitment potential. We surveyed the seed bank along the ecotone across western, central and eastern Florida Bay transects (28 sites); a large reproductive event was also captured at a western site. Seed densities were quantified and seeds characterized into intact (viable and nonviable), germinated and decomposing. Sediment nutrients were also determined from cores at each site. Transect data indicated low seed densities (150–1783m−2) and few viable seeds (0–160m−2) with higher total densities at western and central (643–1783m−2) compared to eastern sites (150–327m−2). In contrast, a meadow undergoing sexual reproduction had high total (25,398m−2) and viable seeds (3556m−2). Total and germinated seeds were also positively predicted by sediment P. While the Everglades ecotone is generally depauperate with respect to R. maritima seeds, an “opportunistic” recruitment strategy sustains it within the community. To restore this species as a highly productive habitat, restoration should focus on R. maritima life history development to seed set, and promoting the development of large reproductive meadows characterized by high seeds densities and a high proportion of viable embryos.