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

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