Rapid enhancement of multiple ecosystem services following the restoration of a coastal foundation species

Abstract

The global decline of marine foundation species (kelp forests, mangroves, salt marshes, and seagrasses) has contributed to the degradation of the coastal zone and threatens the loss of critical ecosystem services and functions. Restoration of marine foundation species has had variable success, especially for seagrasses, where a majority of restoration efforts have failed. While most seagrass restorations track structural attributes over time, rarely do restorations assess the suite of ecological functions that may be affected by restoration. Here we report on the results of two small‐scale experimental seagrass restoration efforts in a central California estuary where we transplanted 117 0.25‐m2 plots (2,340 shoots) of the seagrass species Zostera marina. We quantified restoration success relative to persistent reference beds, and in comparison to unrestored, unvegetated areas. Within three years, our restored plots expanded ~8,500%, from a total initial area of 29 to 2,513 m2. The restored beds rapidly began to resemble the reference beds in (1) seagrass structural attributes (canopy height, shoot density, biomass), (2) ecological functions (macrofaunal species richness and abundance, epifaunal species richness, nursery function), and (3) biogeochemical functions (modulation of water quality). We also developed a multifunctionality index to assess cumulative functional performance, which revealed restored plots are intermediate between reference and unvegetated habitats, illustrating how rapidly multiple functions recovered over a short time period. Our comprehensive study is one of few published studies to quantify how seagrass restoration can enhance both biological and biogeochemical functions. Our study serves as a model for quantifying ecosystem services associated with the restoration of a foundation species and demonstrates the potential for rapid functional recovery that can be achieved through targeted restoration of fast‐growing foundation species under suitable conditions.

Lessons learned from over thirty years of eelgrass restoration on the US West Coast

“…Given the relatively long monitoring duration of eelgrass mitigation projects (Table 2), it is likely that by project completion, many ecosystem functions have indeed returned, and the costs required to monitor a long list of ecosystem functions could be prohibitive. Few studies rigorously evaluate whether biological functions (i.e., biodiversity, nursery function) are enhanced to levels observed in reference habitats following restoration (but see Beheshti et al, 2022; Orth et al, 2020). We encourage practitioners to explore avenues for evaluating habitat use in restored and reference habitats that may be amenable to limited project funding or capacity.…”

“…In mitigation projects, there are typically rigid definitions of success based around meeting predefined shoot density and areal coverage criteria (e.g., the CEMP generally defines success as achieving an areal mitigation ratio of 1.2:1, 100% coverage, and 85% density relative to the reference meadows after 5 years, with unique stipulations throughout the monitoring period and some geographic variability in requirements) (NMFS, 2014). Other projects compare ecosystem attributes related to ecosystem functioning, diversity, and vegetative structure to reference sites (Beheshti et al, 2022; Orth et al, 2020; Ruiz‐Jaen & Aide, 2005). To evaluate restoration success across all projects, we used four definitions of success: Practitioner‐defined shoot density success Practitioner‐defined areal coverage success Shoot density in the last monitoring period ≥ transplanted shoot density Plot area in the last monitoring period ≥ transplanted plot area …”

Sea otters in a California estuary: Detecting temporal and spatial dynamics with volunteer monitoring

“…We suspect that this is due to females with pups using eelgrass beds in this area. Eelgrass beds have expanded in the Wildlife area, in part due to targeted restoration efforts (Beheshti et al, 2021). We hypothesize that the shift of the spring–summer peak from Seal Bend due to Wildlife is linked to eelgrass expansion.…”

Greater Consideration of Animals Will Enhance Coastal Restoration Outcomes

“… 2020 ); and transplanting seagrass in California, in the United States, quickly recovered fish populations (Beheshti et al. 2021 ). Given the likelihood of animals being integral to the long-term health and resilience of restored habitats, ongoing animal monitoring where feasible is recommended and likely beneficial.…”