BIOTIC Species Information for Zostera marina
Researched byDr Harvey Tyler-Walters Data supplied byMarLIN
Refereed byDr Leigh Jones
Reproduction/Life History
Reproductive typeVegetative
Protogynous hermaphrodite
Developmental mechanismOviparous
Reproductive SeasonMay to September Reproductive Location
Reproductive frequencyAnnual episodic Regeneration potential No
Life span21-50 years Age at reproductive maturity1-2 years
Generation time1-2 years FecundityInsufficient information
Egg/propagule size Fertilization type
Larval/Juvenile dispersal potential100-1000m Larval settlement periodNot relevant
Duration of larval stageNot relevant   
Reproduction Preferences Additional InformationZostera sp. are perennials but may act as annuals under stressful conditions (Phillips & Menez 1988). Eelgrass reproduces vegetatively, i.e.. by growth of rhizome. Vegetative reproduction probably exceeds seedling recruitment except in areas of sediment disturbance (Reusch et al. 1998; Phillips & Menez 1988). Examination of the population structure of a Zostera marina bed in the Baltic Sea suggested that individual genotypes (vegetatively produced clones) may be up to 50 years old and further suggested that the eelgrass bed at that site had been present for at least 67 years (Reusch et al. 1998).
    Methods of dispersal:
  • All parts of the plant may float if they become detached from substrate. Pieces of rhizome or shoots (if displaced by for example storm action) may take root if they settle on suitable substratum.
  • The generative stalk may be released together with the seed compliment and may be carried great distances (Phillips & Menez, 1988).
  • In New York, USA, Churchill et al. (1985) recorded 5-13 percent of seeds with attached gas bubbles and achieved an average dispersal distance of 21m and up to 200m in a few cases.
  • Wildfowl may disperse seeds on their feet, or in their gut.. For example, 30 percent of freshwater eelgrass (Naja marina) seeds fed to ducks in Japan survived and successfully germinated after passage through their alimentary canals and potentially transported 100-200km (Fishman & Orth 1996).
Phillips & Menez (1988) state that seedling mortality is extremely high. Fishman & Orth (1996) report that 96 percent of seeds were lost from uncaged test areas due to transport (dispersal) or predation. Ecological genetics studies of Zostera marina in False and Padilla Bays on Pacific coast of USA (Ruckelhaus 1998), detected genetic differentiation between intertidal and subtidal zones and between the bays. Estimates of gene flow suggested that seed dispersal was more important than pollen dispersal, effective migration (2.9 migrants/generation) occurred between the bays (14 km apart) and that the population subdivision was in part explained by disturbance and recolonization. Phillips & Menez (1988) note that seedlings rarely occur within the eelgrass bed except in areas cleared by storms, blow-out or excessive herbivory.
Reproduction References Hartog den, 1970, Phillips & Menez, 1988, Davison & Hughes, 1998, Reusch et al., 1998, Churchill et al., 1985, Stewart et al., 1994, Fishman & Orth, 1996, Rucklehaus, 1998,
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