Macrofaunal biodiversity-ecosystem functioning relationships in seagrass sediments

Abstract

Seagrasses create structurally complex habitat that supports diverse ecological communities and functions but face numerous threats, despite their ecological importance. I investigated how eelgrass, Zostera marina, habitats interact with macrofaunal biodiversity to support carbon and nutrient cycling processes. I experimentally uprooted small seagrass patches and assessed benthic flux rates, macrofaunal biodiversity, and sedimentary variables from sediment cores taken periodically from the uprooted patches, undisturbed seagrass, and unvegetated sediments. Macrofaunal abundance and diversity declined significantly in disturbed treatments, but abundances recovered over three months to resemble natural seagrass and unvegetated treatments. Benthic fluxes varied more over time than among treatments, highlighting seasonal effects on ecosystem functioning. In parallel, I assessed sediment cores from artificial seagrass patches that mimicked seagrass physical structure, natural seagrass, seagrass patch edge, unvegetated habitat, and canopy control treatments. After three months, and though lower than natural seagrass treatments, macrofaunal abundance and diversity in artificial seagrass resembled unvegetated treatments, suggesting that seagrass trophic inputs support macrofaunal biodiversity. In both experiments, minimal macrofaunal diversity effects on benthic flux rates suggest a lesser role for bioturbation in nearshore sandy sediments than in other ecosystems. My results demonstrate that natural seagrass meadows help maintain biodiversity, with potential implications for seagrass conservation.