Effects of Seed Source, Sediment Type, and Burial Depth on Mixed-Annual and Perennial Zostera marina L. Seed Germination and Seedling Establishment
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Seed germination and seedling establishment directly affect the resiliency of seagrasses to disturbance or environmental stress. The objectives of this study were to compare maximum seed germination, time to germination, nongerminated seed viability, and initial seedling biomass between mixed-annual and perennial Zostera marina seed populations in coarse (>90 % sand) and fine (<50 % sand) sediments and at shallow (1 cm) and deep (5 cm) burial depths. Perennial seeds collected from Virginia and North Carolina had greater maximum germination, shorter time to germination, and greater seedling biomass compared to mixed-annual seeds collected from North Carolina. For both mixed-annual and perennial seeds, maximum germination and seedling biomass were the greatest in shallow fine sediments. Mixed-annual seeds buried at 1 cm had a shorter time to germination than in the deep treatments; however, sediment type did not affect mean time to germination. Perennial seeds had a shorter time to germination in shallow compared to deep burial depths and in fine compared to coarse sediments. Cues for germination were present at the deeper depths; however, the cotyledon failed to emerge from the sediment surface resulting in mortality at depths of 5 cm. The greater performance of perennial compared to mixed-annual seeds and seedlings demonstrate the trade-offs which can occur between Z. marina reproductive strategies. Reduced germination of Z. marina seeds buried ≥5 cm and in coarse sediments may represent a possible bottleneck in successful sexual reproduction, feasibly affecting the resiliency to and recovery from disturbance for both perennial and mixed-annual Z. marina beds.
KeywordsZostera marina Mixed-annual Seeds Sediment Viability
The authors would like to thank the National Estuarine Research Reserve Graduate Research Fellowship Program and the Virginia Institute of Marine Science Graduate Research Assistantship Program for funding. Field and laboratory support was also provided by the Center for Coastal Fisheries and Habitat Research, NCCOS, NOS, NOAA. We would also like to thank Erin Shields, Brittany Haywood, and Brandon Jarvis for field and laboratory assistance. This is contribution number 3391 of the Virginia Institute of Marine Science, College of William & Mary.
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