Lack of Natural Seagrass Recovery at a Site in the Eastern Tropical Pacific Reveals the Need for Active Ecological Restoration

Abstract

Seagrass meadows provide many ecosystem services, but by virtue of anthropogenic pressures, they are also highly threatened habitats. In the Eastern Tropical Pacific, a seagrass meadow disappeared in 1996 following a severe storm at Bahía Culebra, northern Pacific coast of Costa Rica. This study aimed to assess natural recovery of this seagrass meadow and identify potential factors influencing habitat condition. A field assessment was carried out in 2023, to assess seagrass presence or absence at the site, collect biomass cores to check for potential presence of belowground biomass, collection of sediment for grain size analysis, evaluation of water quality conditions, deployment of grazer exclusion cages, and incubation of sediment in aquaria conditions to assess potential seed germination. There was no seagrass biomass or seagrass cover noted within the bay in 2023. Incubated sediment did not lead to seed germination, and no seeds were found in the sediment following incubation. Water conditions and sediment grain sizes were within parameters for other meadows nearby yet revealed decreased water conditions at this site compared to previous ones in 2000-2001. Water quality varied temporally, consistent with natural seasonal upwelling in the bay. Conditions were suitable for seagrasses, yet other potential dispersal and establishment-limiting factors, such as water flow dynamics, sediment biogeochemistry, and microbial communities, should be assessed at higher spatial and temporal frequencies in the future. Given the lack of natural recovery in 27 years and apparent recent suitable seagrass conditions, active seagrass ecological restoration initiatives are recommended at this site.