Seagrass meadows are important sources of reef island-building sediment

Abstract

The future vulnerability of low-lying atoll nations is inextricably linked to the production of island-building carbonate sediments by organisms living in their adjacent marine environments. Seagrass meadows are commonly found adjacent to reef islands, but their potential role as sources of reef island-building sediments has been overlooked. Here, we quantify rates of sediment production by seagrass epibionts in a reef island sediment supply context. Total seagrass epibiont sediment production at our study site (Huvadhoo Atoll, Maldives) was 853,000 ± 90,000 kg CaCO3 yr-1 over an area of 1.1 km2. Of this total sediment production, 541,000 ± 23,000 kg CaCO3 yr-1 was estimated to be suitable to contribute to reef island building (i.e., sand-sized, post-agitation). Our findings highlight a previously unrecognised and highly valuable ecosystem service provided by tropical seagrass meadows as important potential sources of reef island-building sediment. This study, therefore, presents a new and compelling geomorphic argument for seagrass conservation.