Abstract
Seagrass cover is declining worldwide, and successful management, conservation and restoration require a complete understanding of individual species’ life histories. The historically undervalued importance of sexual reproduction in seagrass population dynamics has prompted investigations of reproductive phenology and output. Here, we present the results of a multi-year study examining the reproductive phenology and output of two dominant seagrass species in the northwest Gulf of Mexico, Thalassia testudinum (turtle grass) and Halodule wrightii (shoal grass). We assessed flowering, fruit and seed production, seed reserve density and plant biomass in several locations along the central Texas coast. Results indicate that reproductive timing and output are heterogeneous over both small and large spatial scales and across years. The percentage of flowering and fruit-bearing T. testudinum shoots ranged from 0% to 15% and 0% to 10%, respectively, and fruit densities ranged from 0 to 180 fruits m−2. Average biomass allocated to reproductive structures for flowering T. testudinum shoots ranged from ~27% to 42%. High-density H. wrightii seed reserves (3950 seeds m−2) were localized and exhibited substantial variation among sites, but average site-specific seed densities were lower (0–611 seeds m−2). The results of this study can inform restoration efforts and emphasize the need for understanding factors that influence reproductive timing and output for these species.
About the authors
Kelly M. Darnell is a research scientist at The Water Institute of the Gulf in Baton Rouge, Louisiana. Her research focuses on the functional role of submerged, floating and emergent coastal plants as habitat and food for nearshore animals, submerged plant reproductive ecology, and ecological consequences of complexity across scales.
Kenneth H. Dunton is a professor at The University of Texas at Austin Marine Science Institute in Port Aransas, Texas. His research focuses on the productivity of coastal ecosystems at mid- and high latitudes, trophic ecology and the ecological response and resilience of benthic communities to environmental change.
Acknowledgments
We thank K. Jackson, V. Congdon, S. Wilson, N. McTigue and P. Bucolo for assistance in the field and laboratory. We also thank the Mission-Aransas National Estuarine Research Reserve for logistic support. Two anonymous reviewers provided helpful comments that greatly improved this manuscript. This study was funded by the Estuarine Reserves Division, Office of Ocean and Coastal Resource Management, National Ocean Service, National Oceanic and Atmospheric Administration (Grant number NA11NOS4200082), an E.J. Lund Marine Science Research Fellowship and a Scholar Award from P.E.O. International.
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