BIOTIC

BIOTIC Species Information for Zostera noltii

Researched by

Dr Harvey Tyler-Walters

Data supplied by

MarLIN

Refereed by

Dr Leigh Jones

Reproduction/Life History

Reproductive type

Vegetative
Protogynous hermaphrodite

Developmental mechanism

Oviparous

Reproductive Season

May to September

Reproductive Location

Reproductive frequency

Annual protracted

Regeneration potential

Life span

1 year

Age at reproductive maturity

1-2 years

Generation time

1-2 years

Fecundity

Insufficient information

Egg/propagule size

Fertilization type

Larvae/Juveniles
Larval/Juvenile dispersal potential	100-1000m	Larval settlement period	Not relevant
Duration of larval stage	Not relevant

Reproduction Preferences Additional Information

Zostera sp. are monoecious perennials but may be annuals under stressful conditions (Phillips & Menez 1988). Hootsmans et al. (1987) reported that each flowering shoot of Zostera noltii produces 3-4 flowers containing 2-3 seed each. They estimated a potential seed production of 9000/m² based on the maximum density of flowering shoots in their quadrats in the Zandkreek, Netherlands. Most seeds were released in August in the Zandkreek but the actual seed densities were much lower than predicted (Hootsmans et al., 1987). However, the density of flowering shoots is highly variable. 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). Phillips & Menez (1988) state that seedling mortality is extremely high. Fishman & Orth (1996) report that 96% of Zostera marina seeds were lost from uncaged test areas due to transport (dispersal) or predation. Hootsmans et al. (1987) noted that potential recruitment was maximal (32% of seeds) at 30 °C and 10psu, and no recruitment occurred at 30psu. and they estimated that, in 1983 <5% of Zostera noltii plants in the Zandkreek originated from seed. Phillips & Menez (1988) note that seedlings rarely occur within the eelgrass beds except in areas cleared by storms, blow-out or excessive herbivory. Den Hartog (1970) noted that although the seed set was high, Zostera noltii seedlings were rarely seen in the wild, suggesting that vegetative reproduction may be more important than sexual reproduction (Davison & Hughes, 1998). Experimental germination was increased by low salinity (1-10 psu) in Zostera noltii and no germination occurred at salinities above 20 psu, however germination was independent of temperature (Hughes et al., 2000).
Sexual reproduction
Zostera sp. flowers release pollen in long strands, dense enough to remain at the depth they were released for several days, therefore, increasing their chance of pollinating receptive stigmas. Seeds develop within a membranous wall that photosynthesises, developing an oxygen bubble within the capsule, eventually rupturing the capsule to release the seed. Seeds generally sink and may be dispersed by currents and waves (perhaps aided by air bubbles) and the feet or gut of birds.
Methods of dispersal:

All parts of the plant may float if they become detached from substratum. Pieces of rhizome or shoots (if displaced by for example storm action) may take root if they settle on suitable substrata (Phillips & Menez, 1988).
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% of Zostera marina 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% 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).

Reproduction References

Phillips & Menez, 1988, Davison & Hughes, 1998, Hartog den, 1970, Marta et al., 1996, Nacken & Reise, 2000, Dawes & Guiry, 1992, Hughes et al., 2000, Holt et al., 1997, Churchill et al., 1985, Fishman & Orth, 1996, Olesen & Sand-Jensen, 1993, Hootsmans et al., 1987,