Influence of a tube-dwelling polychaete on the dispersal of fragmented reproductive shoots of eelgrass

Diopatra cuprea (Bosc), a common tube-building polychaete, attaches materia ls such as algae and shell into the wall of its tube cap, in part, to provi de a substrate for potential food resources. Reproductive shoots of eelgras s (Zostera marina L.) break off juring seed maturation and can be transport ed by water movement. As these shoots deteriorate, they become neutrally or negatively buoyant and can be transported alone the bottom while still car rying seeds. Analysis of 55 1 m(2) plots along a 100 m transect in the offs hore fringe of an eelgrass bed in the York River, Chesapeake Bay, USA, show ed that 70% of D. cuprea had fragmented reproductive shoots built into thei r tube cap walls, with a highly significant regression of shoot to tube den sity (r(2) = 0.76). There was a positive correlation between seedlings and tube caps (r(2) = 0.39). D. cuprea may alter hydrodynamics, arresting trans port of fragmented reproductive shoots, thereby potentially influencing pat ch and bed dynamics in both near and distant regions from existing beds. (C ) 2001 Elsevier Science B.V. All rights reserved.