Communities of sabellariid worms (Polychaeta) occur as areally discontinuous, unlithified reefs on an irregular depositional topography of Holocene and older sediments at the mouth of the Northern River Lagoon, Belize, Central America. Based upon radiocarbon dating of peat deposits, and analyses of sediment cores, the worm reefs have flourished in the study area of at least 5100 yr. This time span corresponds with sea level rise and transgression of the northern Belize coast. Initially, worms colonized drowned levees. Once established, the worm reefs stabilized these levees so that their original orientation normal to shore line is preserved today. -from Authors