Evaluation of Relationships between Biodiversity and Ecosystem Functions in Coastal Seas: A Case Study of Seagrass Beds in Tokyo Bay

Abstract

Recent analyses of ecological experiments conducted at small spatial scales have revealed that biodiversity measured at various biotic levels, i.e., species and landscape diversity, plays important roles in maintaining various functions of coastal ecosystems. To test whether the same relationship can be found at broader spatial scales, we measured various indices of biodiversity and functions of seagrass beds located along the eastern shore of Tokyo Bay. Based on our field survey and literature information, we collected data on three variables representing biodiversity of seagrass beds, i.e., mean allele richness of eelgrass obtained using microsatellite analysis, species richness of seagrasses, and Simpson's diversity index for epifaunal assemblages. We also obtained data on three variables representing functions of seagrass beds, i.e., bed areas and their temporal variation, and abundance of epifaunal assemblages. Correlation analysis revealed that allele richness was positively correlated with seagrass bed area, and that seagrass species richness tended to increase with seagrass bed area. In contrast, diversity of epifauna tended to decrease with increasing abundance, although this could be ascribed to a massive occurrence of mysids in one seagrass bed. The findings suggest that biodiversity measured at multiple levels is related to environmental settings and functions of seagrass beds, and that this relationship can be used for the evaluation of seagrass bed condition for conservation and management purposes.