Density and distribution of seeds in bottom sediments in Zostera marina beds in Ago Bay, central Japan

Morita, Teruwo; Okumura, Hiroyuki; Kurashima, Akira; Maegawa, Miyuki

doi:10.1016/j.aquabot.2007.03.001

Cited by 26 publications

(17 citation statements)

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“…At NC1 and NC2 the seed bank density declined so that by the fall of 2008, following the period of maximum germination for this region (Silberhorn et al 1983, Thayer et al 1984, < 2% of that year's estimated seed production remained viable in the sediment. Similar large losses of seeds, ranging from 25 to 78% of total seed production, have been reported for both annual and perennial Zostera marina beds (Santamaría-Gallegos et al 2000, Harwell & Orth 2002b, Morita et al 2007). These losses may be the result of dispersal (Harwell & Orth 2002a, Källström et al 2008, decay (Morita et al 2007), predation (Fishman & Orth 1996), or germination (Harper 1977).…”

Section: Attributes Of a Mixed-annual Life Historysupporting

confidence: 75%

Characterization and ecological implication of eelgrass life history strategies near the species’ southern limit in the western North Atlantic

Jarvis¹,

Moore²,

Kenworthy³

2012

Mar. Ecol. Prog. Ser.

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Eelgrass Zostera marina L. populations located near the species southern limit in the western North Atlantic were assessed monthly from July 2007 through November 2008. We identified (1) dominant life history strategies and local environmental conditions in southern Z. marina populations, (2) quantified differences in reproductive phenology between populations and different local environmental conditions, and (3) compared reproductive strategies to established annual and perennial life history paradigms. Observed populations expressed both life history strategies with one Z. marina population completely losing aboveground biomass and reestablishing from seeds (annual model) while another population retained aboveground biomass throughout the year (perennial model). A third life history strategy, characterized here as a mixed-annual population, was also observed after some seedlings were found to reproduce both sexually and asexually during their first year of growth thereby not conforming to any currently established life history paradigm. Development of multiple life history strategies within this region may be in response to stressful summer water temperatures associated with the southern edge of the species' range. We suggest that neither annual nor perennial life history strategies always provide a superior mechanism for population persistence as perennial populations can be susceptible to multiple consecutive years of stress, and annual populations are unable to fully exploit available resources throughout much of the year. The mixed-annual strategy observed here represents another possible life history model which may provide the mechanism necessary for Z. marina populations to persist during times of environmental transition.KEY WORDS: Zostera marina · Life-history · Annual · Perennial · Seed bank · Biomass Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 444: [43][44][45][46][47][48][49][50][51][52][53][54][55][56] 2012 populations have also been documented to express behavior similar to the biennial life history model (Setchell, 1929). After germinating, seedling growth in biennial populations occurred via clonal expansion only and flowering stem development and fruiting were not observed until after a period of 1 to 2 yr of growth (Setchell 1929;Thayer et al. 1984). More recently an annual life history strategy has been described for Z. marina populations, where mature plants consist of reproductive (flowering) shoots only and all plants complete their life cycle (seeds germinate, flower, produce seeds) and die within 12 mo (Keddy & Patriquin, 1978, Gagnon et al. 1980, De Cock 1981, Harlin et al. 1982, Phillips et al. 1983a, Robertson & Mann 1984, Santamaría-Gallegos et al. 2000.Although they have been documented throughout the species' geographic distribution, annual forms of Zostera marina are primarily found in areas characterized by stressful environmental conditions such as ice scour (Robertson & Mann 1984), extreme temperatures (Phillips...

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Section: Attributes Of a Mixed-annual Life Historysupporting

confidence: 75%

Characterization and ecological implication of eelgrass life history strategies near the species’ southern limit in the western North Atlantic

Jarvis¹,

Moore²,

Kenworthy³

2012

Mar. Ecol. Prog. Ser.

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“…Flowering within Z. marina beds is not homogeneous, resulting in a non-even distribution of seeds within the sediment seed-bank (Harwell & Orth, 2002;Morita et al, 2007). Z. marina seeds typically do not germinate immediately after release from the reproductive shoot (Taylor, 1957;Keddy 1987;Harrison, 1993;Moore et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

The role of seedlings and seed bank viability in the recovery of Chesapeake Bay, USA, Zostera marina populations following a large-scale decline

Jarvis

Moore

2010

Hydrobiologia

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The objective of this study was to quantify the spatial and temporal recolonization characteristics of Zostera marina beds in the lower Chesapeake Bay following large scale declines in the late summer of 2005. Transects were established and monitored monthly for changes in eelgrass abundance at three sites (two downriver, one upriver) in the York River from April-October 2006 and 2007. Measurements included percent bottom cover, above ground biomass, shoot density, shoot origin (seedling or vegetative), seed bank abundance and seed viability. During 2006, the eelgrass beds at all sites recovered with seedlings providing the largest proportion of the total shoot abundance. This trend shifted in 2007 and surviving vegetative shoots were the dominant component of shoot standing crop. A second consecutive decline related to low light conditions occurred during the summer of 2006 in the upriver site and recovery there was minimal in 2007. These results highlight that after a single die off event, seed germination with subsequent seedling growth is the principal method for revegetation in lower Chesapeake Bay Z. marina beds. However, no viable seeds remain in the seed bank during this first year of recovery and shoots produced by the seedling growth do not flower and produce seeds until their second year of growth. Therefore the seed-bank density is low and is not immediately replenished. This suggests that the resiliency of perennial Chesapeake Bay Z. marina populations to repeated disturbances is restricted and repeated annual stress may result in much longer term bed loss.

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“…The sampling outside of the vegetated area was conducted within approximately 1.5 m of the edge of the eelgrass bed. Because eelgrass seeds have been reported to be buried to approximately ≤10 cm (Morita et al 2007), seeds were sampled from the sediment to a depth of at least 10 cm. To determine seed survivorship from the previous year, the abundances of seeds and seed-coat fragments within the eelgrass bed were measured via SCUBA in May 2010, before seeds were dispersed, using a shovel (area: 0.031 m 2 ; sampling depth, at least 10 cm; n = 5).…”

Section: Seeds In the Sedimentmentioning

confidence: 99%

Seed dispersal in the seagrass Zostera marina is mostly within the parent bed in a protected bay

Hosokawa¹,

Nakaoka²,

Miyoshi³

et al. 2015

Mar. Ecol. Prog. Ser.

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Seed production and dispersal are key processes in plant population dynamics and gene flow. However, few quantitative studies have followed these processes in aquatic plants. We investigated the abundance of seeds produced and dispersed by the seagrass Zostera marina L. at a protected site within an enclosed bay. We also examined the buoyancy potential of seed dispersal units (diaspores) in the laboratory. Field observations showed that 31% of the total potentially produced seeds were dispersed as decayed reproductive shoots on the sea bottom of the parent bed, whereas 14% were dispersed in spathes (a component of reproductive shoots; seeds are contained inside) detached from live reproductive shoots. However, more than half of the dispersed spathes were negatively buoyant because of the weight of the ripe seeds they contained. Thus, < 6% of potentially produced seeds were dispersed by rafting away from the parent bed. The abundance of ripe seeds dispersed was comparable to that of seeds in the parent bed sediment. The fate of the remaining 54% of total potentially produced seeds was not detected, and they were assumed to be immature or to have been consumed by herbivores. Fewer than 5% of the dispersed seeds had germinated. Our results show that most seeds were dispersed within the parent bed, supporting one of the fitness-related seed-dispersal hypotheses, namely that dispersal mechanisms play a role in bed maintenance and increased genetic diversity.

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Density and distribution of seeds in bottom sediments in Zostera marina beds in Ago Bay, central Japan

Cited by 26 publications

References 27 publications

Characterization and ecological implication of eelgrass life history strategies near the species’ southern limit in the western North Atlantic

Characterization and ecological implication of eelgrass life history strategies near the species’ southern limit in the western North Atlantic

The role of seedlings and seed bank viability in the recovery of Chesapeake Bay, USA, Zostera marina populations following a large-scale decline

Seed dispersal in the seagrass Zostera marina is mostly within the parent bed in a protected bay

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