Seed reserves and seed germination for two seagrasses, Halodule wrightii and Syringodium filiforme, from the western Atlantic

Abstract

Seeds of Halodule and Syringodium from diverse sites in the western Atlantic showed low rates of germination over extended periods of time. Seeds of Halodule are suited to long-term dormancy, possibly extending over many years, while those of Syringodium are oriented toward short-term dormancy. For Halodule, dormancy involves both seed coats and embryos, but for Syringodium, it probably involves only seed coats. Germination for both seagrasseoccurs in a wide range of salinities: 5–50‰ for Halodule; 20–50‰ for Syringodium. One-seeded fruits of Halodule are produced at rhizome level and remain buried in the sediment until disturbed and constitute a seed reserve estimated at a maximum of ca. 3000 m −2 in both Texas in the U.S. Virgin Islands. Syringodium fruits (one-seeded) are produced on inflorescences elevated above the sediment at a maximum rate of ca. 10 000 m −2, but few reserves in the sediment were recorded. The dormancy of seagrass seeds permits germination over extended periods of time and allows survival in disturbed sites as well as colonization of new habitats.