MEPS 267:121-131 (2004)  -  doi:10.3354/meps267121

ABSTRACT: Thalassia testudinum seedling recruitment, survival, and growth were examined within physically disturbed seagrass beds in the Florida Keys. Two separate studies were conducted. In the first, a large-scale study, T. testudinum seedlings were surveyed and collected from a large seagrass disturbance (1560 m²), 4.8 yr after the initial impact from a motor-vessel grounding. In the second, a smaller-scale study, T. testudinum seedling recruitment was examined over a 2 yr period within 9 smaller motor-vessel disturbances located within intact T. testudinum beds. In the large-scale study, we reconstructed the age of the seedlings based on shoot production rates from a previous study and from the small-scale study. A total of 79 seedlings were collected that varied in age from young of the year to 4.8 yr old; 6 different seedling cohorts were identified. The average density and rhizome-elongation rate for 1 yr old seedlings were 1 m^-2 and 6.6 cm yr^-1, respectively. In the small-scale study, we surveyed and permanently marked all newly recruited seedlings; monitoring was conducted 5 more times over a 2 yr period. The average seedling survival after Year 1 was 42%; after Year 2, average survival dropped to 20%. The average seedling density after Year 1 was 0.071 m^-2; after Year 2, average density dropped to 0.026 m^-2. The average rhizome-elongation rate and shoot-production rate of 1 yr old seedlings were 6 cm yr^-1 and 1.8 shoots yr^-1, respectively. The results of this study suggest that T. testudinum seedlings are a regular and reliable source of new recruits on seagrass banks in the Florida Keys.

KEY WORDS: Thalassia testudinum · Seedling · Disturbance · Succession · Seagrass · Recovery process · Sexual reproduction