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Marine Ecology Progress Series

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MEPS 310:109-117 (2006)  -  doi:10.3354/meps310109

Fragments of the seagrasses Halodule wrightii and Halophila johnsonii as potential recruits in Indian River Lagoon, Florida

Lauren M. Hall1,*, M. Dennis Hanisak2, Robert W. Virnstein3

1St. Johns River Water Management District, 525 Community College Parkway, Palm Bay, Florida 32909, USA
2Harbor Branch Oceanographic Institution, 5600 US 1 North, Fort Pierce, Florida 34946, USA
3St. Johns River Water Management District, 4049 Reid Street, Palatka, Florida 32177, USA

ABSTRACT: The role of vegetative seagrass fragments as a dispersal and recruitment mechanism has received little attention. Research on the potential of vegetative fragments as a dispersal mechanism can help us better understand the ability of seagrass beds to recover from disturbance events, to recruit into new areas, and to survive over long periods. The objectives of this study were to (1) determine the viability of vegetative fragments of Halodule wrightii and Halophila johnsonii as a function of time after removal from sediment, (2) determine whether season of collection affects the fragments’ recruitment potential, (3) determine if the source of fragments of H. johnsonii affects viability, (4) determine how long fragments float, and (5) determine the frequency of fragment settlement and rooting vs. time. Mesocosm experiments with plants collected from Indian River Lagoon, Florida demonstrated that fragments of H. wrightii remain viable during spring for up to 4 wk with a marked decline in survival after 2 wk of drifting. Fall plants had a shorter period of viability with only 5% of fragments remaining viable by Week 2. Although the source location of the fragments did not influence viability for H. johnsonii, day and season were highly significant for viability, with spring plants remaining viable for up to 4 d and fall plants remaining viable for twice as long. The short viability of H. johnsonii illustrates the importance of rapid settlement when uprooted from a source bed, limiting dispersal to short distances. H. wrightii appears to maintain its viability for a longer period of time, indicating that this species may be able to utilize fragments as a dispersal mechanism over longer distances. The vegetative fragments of both H. wrightii and H. johnsonii had the ability to settle and root in mesocosms, demonstrating that fragmentation is a viable mechanism for dispersal and recruitment for these species.

KEY WORDS: Seagrass recruitment · Vegetative fragmentation · Halophila johnsonii · Halodule wrightii · Indian River Lagoon

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