GROWTH-PATTERNS AND DEMOGRAPHY OF PIONEER CARIBBEAN SEAGRASSES HALODULE-WRIGHTII AND SYRINGODIUM-FILIFORME

The shoot demography and rhizome growth of Syringodium filiforme Kutz. and Halodule wrightii Aschers. were studied, based on plant dating te chniques, to account for their role as pioneer in the succession seque nce of Caribbean seagrasses. Results demonstrated that these species a re able to develop dense meadows, supporting biomasses in excess of 50 0 g DW m-2. They produced more than 2000 g DW M-2 yr-1 due to their hi gh leaf (5.0 to 8.5 yr-1) and rhizome (2.0 to 3.3 yr-1) turnover. Rhiz ome growth and branching rates were very high, allowing these seagrass es to rapidly occupy the space they colonise. The rapid rhizome turnov er involved, however, a high shoot mortality rate and low life expecta ncy (average shoot life expectancy 100 to 180 d). This implies that, w hile these pioneer species are able to rapidly occupy the space they c olonise, their established shoots cannot occupy that space for as long as the more long-lived species Thalassia testudinum. We suggest, ther efore, that the role of seagrass species as pioneer or climax species is independent of their capacity to support dense, productive populati ons, and is closely related to shoot longevity and rhizome turnover.