Seagrass colonization: biomass development and shoot demography in Cymodocea nodosa patches

Abstract

Patches of Cymodocea nodosa colonizing highly mobile sandy sediments were studied to determine the temporal and spatial course of biomass and demographic development. Results show (1) a close coupling between rhizome growth and shoot density and biomass; (2) an average b ~ o n ~ a s s accumulation rate of ca 250 g fresh wt m-2 yr-l for rhizomes and 480 g m-2 yr-' for shoots; and (3) a close relationship between plant biomass and distance from patch edge Short shoots are produced in annual cohorts, subject to an average mortality of ca 1.0 exponential unit yr-' regardless of cohort age, but shoot mortality decreases with distance from patch edge. Patch maintenance is achieved by shoot recruitment rates closely matching shoot mortality rates. Mean shoot age, variability in shoot age structure, and associated shoot characteristics (i.e. length and number of standing leaves), increase with time after patch establishment. These results demonstrate the importance of shoot recruitment and mortality for the maintenance and growth of C. nodosa patches and, hence, for seagrass recovery.