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Overview

Brief Summary

Eelgrass is a seed plant and not a seaweed. It has roots and seeds just like land plants. Mattresses and cushions filled with eelgrass, dikes made from eelgrass for defending the land from the sea - just some of the ways this plant was used before it practically disappeared in the Wadden Sea, Zuiderzee and Delta region. Lots of eelgrass grew in the waters surrounding Wieringen, giving the island its name. The 'wier' was eelgrass. In earlier times, it was harvested and formed a major source of income for residents of the islands. It was a disaster for them when the large eelgrass habitats disappeared, after the closure of the Afsluitdijk.
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Comprehensive Description

Eelgrass (Zostera marina) is a marine angiosperm (flowering plant) of great importance in the Northern Hemisphere. It plays important roles in sediment deposition, substrate stabilization, as substrate for epiphytic algae and microinvertebrates, and as nursery grounds for many species of economically important marine vertebrates and macroinvertebrates. Historically, it was at one time the principle material for the Dutch dikes and has been used as stuffing for mattresses and cushions. (Haynes 2000) Felger and Moser (1973) reported on the use of Eelgrass seeds as food by the Seri Indians, traditional hunters and gatherers of Sonora, Mexico. According to the authors, this is the only known case of a grain from the sea being used as a human food source.

In the 1930s, Zostera marina suffered dramatic die-offs on the Atlantic coasts of North America and Europe. The plants would develop large brown spots on the leaves and rhizomes and slowly die. This "wasting disease" eventually led to the disappearance of most of the eelgrass in the North Atlantic, along with much of the fauna that depended on it (Short et al. 1987; Haynes 2000). Over the decades, Eelgrass gradually re-established itself in many (though not all) of the areas it had previously occupied. The cause of the widespread wasting disease has been established to be a fungus-like protist, Labyrinthula zosterae, which dramatically reduces photosynthetic capability (Ralph and Short 2002). Wasting disease continues to affect Eelgrass meadows in North America and Europe with variable degrees of loss, though none to date as catastrophic as the epidemic of the 1930s (Short et al. 1987; Ralph and Short 2002).

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Description

 Grass like flowering plant with dark green, long, narrow, ribbon shaped leaves 20-50 cm in length (exceptionally up to 2 m long) with rounded tips. Leaves shoot from a creeping rhizome that binds the sediment.  Leaves and rhizomes contain air spaces, lacunae, that aid buoyancy. Numerous flowers occur on a reproductive shoot similar to those of terrestrial grasses. Forms dense swards in the subtidal, supports a diverse fauna and flora and may act as a nursery for fish and shellfish.Other common names include, wigeon grass, broad leaved grass wrack, marlee, sedge and slitch. Perennial populations show a seasonal changes in leaf growth, the long leaves found in summer are replaced by shorter, slow growing leaves in winter. The morphological characteristics, especially leaf width may vary with environmental conditions (Phillips & Menez 1988). In the UK literature Zostera marina is distinguished from Zostera angustifolia on the basis of morphology. However, outside the UK most authors consider Zostera angustifolia to be a phenotypic variant of Zostera marina. To avoid confusion only data relating to Zostera marina is presented.
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Distribution

National Distribution

Canada

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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Range Description

Zostera marina is widespread and circumglobal in northern latitudes, found throughout the north Atlantic and north Pacific and in the Mediterranean and Black Seas. Zostera marina extends into the Arctic in Alaska, Canada, Greenland, and northern Europe and to the tropics in Baja California, Mexico.
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B.C., N.B., Nfld. and Labr. (Nfld.), Nunavut, N.S., Ont., P.E.I., Que., Yukon; Alaska, Calif., Conn., Del., Maine, Md., Mass., N.H., N.Y., N.C., Oreg., R.I., Va., Wash.; Mexico (Baja California, Sinaloa, Sonora); Eurasia.
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Zostera marina is found along both coasts of North America from Alaska and northern Canada south to Baja California on the Pacific coast and North Carolina on the Atlantic coast, as well as in Eurasia (Haynes 2000).

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Physical Description

Morphology

Description

Herbs, perennial. Rhizomes 2--6 mm thick; roots 5--20 at each node. Leaves: sheath tubular, rupturing with age, 5--20 cm, membranous flaps absent; blade to 110 cm ´ 2--12 mm, apex round-obtuse or slightly mucronate; veins 5--11. Generative shoots terminal, repeatedly branched, each branch with 1--5 spathes. Inflorescences: peduncles with adnate portion 15--100 mm, free portion 2--3 cm; spathes 10 or more, sheath 4--8 cm ´ 2--5 mm; blade 5--20 cm; spadix linear; staminate flowers 1--20; pistillate flowers 1--20, apex acute or mucronate. Staminate flowers: bracts absent or rarely 1 subtending most proximal flower; pollen sacs 4--5 ´ 1 mm. Pistillate flowers: ovary 2--3 mm, style 1--3 mm. Fruits ellipsoid to ovoid, 2--5 mm, often beaked.
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Diagnostic Description

Synonym

Zostera marina var. stenophylla Ascherson & Graebner
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
In Scandinavia and UK, this is the most widely distributed seagrass, dominates sandy and muddy sediments in coastal areas of low to moderate wave exposure. In southernmost Sweden it flourishes on stony and sandy bottoms at 2-4 m depth. It has a wide salinity tolerance of 5-35 ppt. In the western Baltic Sea it occurs along exposed sandy shores and in long bays and shallow lagoons with reduced water exchange and muddy substrate. Has a facultative mutualism with blue mussels (Mytilus edulis) in shallow waters (1-3 m depth).

This species is commonly grazed by isopods (Idotea spp.) and snails (Hydrophobia spp., Littorina spp.). It is also consumed by birds, especially Mute Swans (Cygnus olor) in shallow lagoons.

This is a relict species in the Mediterranean, where it forms perennial meadows distributed from the intertidal to a few meters deep. In the Black Sea, Z. marina is found in pure and mixed stands from 0.5-15 m depth on silty-sandy substrates. It has 80-100% cover in its beds and shoot density of 988/m². It has 115 species of macroalgae associated with it (Milchakova 1999). Zostera marina occurs regularly in coastal lagoons of the western Mediterranean (Laugier et al. 1999) where it is often found with Z. noltii.

In Japan, occurs in the shallowest parts of subtidal beds, mostly between 1-5 m deep, but in some places down to 10 m. Flowering and fruiting seasons vary by 2-4 months across Japan, with early flowering and fruiting observed at lower latitudes. In South Korea, appears at the intertidal and subtidal zones, where the water depth is usually less than 5 m, and forms relatively large meadows and can be observed in both muddy and sandy sediments. It accounts for about 90% of total seagrass coverage in Republic of Korea.

Zostera marina is the dominant species in terms of biomass and habitats in the Pacific coast of North America, where it grows in the shallow waters of the continental shelf, the Gulf of California, coastal lagoons, estuaries and coastal fjords. Can co-mingle with Zostera japonica in the Pacific Northwest and Ruppia maritima in Baja California. Overwhelmingly dominant seagrass in coastal and estuarine areas of the western North Atlantic, found in both intertidal and subtidal areas, from a depth of +2 m to -12 m mean sea level. Distribution ranges from the protected low-salinity (5 ppt) waters of inner estuaries and coastal ponds to high-energy locations fully exposed to the Gulf of Maine and the North Atlantic with salinity of 36 psu (Green and Short 2003).

Systems
  • Marine
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Intertidal to sublittoral of marine waters; -10--0m.
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Depth range based on 117 specimens in 1 taxon.
Water temperature and chemistry ranges based on 7 samples.

Environmental ranges
  Depth range (m): 0 - 27.43
  Temperature range (°C): 11.768 - 12.348
  Nitrate (umol/L): 4.729 - 7.121
  Salinity (PPS): 35.184 - 35.363
  Oxygen (ml/l): 6.069 - 6.151
  Phosphate (umol/l): 0.351 - 0.439
  Silicate (umol/l): 2.489 - 3.285

Graphical representation

Depth range (m): 0 - 27.43

Temperature range (°C): 11.768 - 12.348

Nitrate (umol/L): 4.729 - 7.121

Salinity (PPS): 35.184 - 35.363

Oxygen (ml/l): 6.069 - 6.151

Phosphate (umol/l): 0.351 - 0.439

Silicate (umol/l): 2.489 - 3.285
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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 Dense swards found primarily on sand to fine gravel in the subtidal, typically down to 4 m, in sheltered waters such as shallow inlets, bays, estuaries and saline lagoons.
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Associations

Foodplant / feeds on
larva of Macroplea mutica feeds on root of Zostera marina
Remarks: Other: uncertain

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Life History and Behavior

Cyclicity

Flowering/Fruiting

Flowering late spring--summer.
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Zostera marina

The following is a representative barcode sequence, the centroid of all available sequences for this species.


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Statistics of barcoding coverage: Zostera marina

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 11
Specimens with Barcodes: 12
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: N4 - Apparently Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2010

Assessor/s
Short, F.T., Carruthers, T.J.R., Waycott, M., Kendrick, G.A., Fourqurean, J.W., Callabine, A., Kenworthy, W.J. & Dennison, W.C.

Reviewer/s
Livingstone, S., Harwell, H. & Carpenter, K.E.

Contributor/s

Justification
This species is widespread, circumglobal in the Northern hemisphere. There have been documented localized declines in parts of the range, but not sufficient to warrant placement in a threatened category. Zostera marina is listed as Least Concern.
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Population

Population
There are regions of large scale decline for Zostera marina (wasting disease and major pollution threats), areas where there has been no decline and the population is thriving, and areas of complete disappearance. This species is a widespread and dominant species, usually monospecific meadows. It has declines mostly in developed and populated areas in Europe and North America.

Ongoing restoration efforts since the 1940s in Europe and North America transplanted to re-establish populations of eelgrass in part of their former range from which they had been extirpated.

There has been a global decline of area covered by Zostera marina by 1.4% per year based on 126 documented changes in area that have been conducted over a 10 year period from 1990-2000.

Population Trend
Decreasing
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Threats

Major Threats
There have been local declines in many regions due to loss of water clarity from sedimentation, coastal development and wasting disease. Nutrient loading from runoff has also resulted in some local declines.
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Management

Conservation Actions

Conservation Actions
There are no specific conservation measures in place for this species, but it has general protection under coastal habitat conservation laws and where it occurs in protected areas.
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Relevance to Humans and Ecosystems

Benefits

Economic Uses

Uses: MEDICINE/DRUG

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Wikipedia

Zostera marina

Zostera marina is a species of seagrass known by the common names common eelgrass and seawrack. It is an aquatic plant native to marine environments on the coastlines of mostly northern sections of North America and Eurasia. It is the most wide-ranging marine flowering plant in the Northern Hemisphere.[1] It lives in cooler ocean waters in the North Atlantic and North Pacific, and in the warmer southern parts of its range it dies off during warmer seasons.[2] It grows in the Arctic region and endures several months of ice cover per year.[3] It is the only seagrass known from Iceland.[3] It can be found in bays, lagoons, estuaries, on beaches, and in other coastal habitat. There are several ecotypes, each with specific habitat requirements.[4] It occurs in calmer waters in the sublittoral zone where it is rarely exposed to air.[2] It anchors via rhizome in sandy or muddy substrates and its leaves catch particulate debris in the water which then collects around the bases of the plants, building up the top layer of the seabed.[2]

This flowering plant is a rhizomatous herb which produces a long stem with hairlike green leaves that measure up to 1.2 centimeters wide and may reach over a meter long. It is a perennial plant but it may grow as an annual.[5] The rhizome grows horizontally through the substrate, anchoring via clusters of roots at nodes.[2] The plant is monoecious, with an individual bearing both male and female flowers in separate alternating clusters. The fruit is a nutlet with a transparent coat containing the seed. The plant can also undergo vegetative reproduction, sprouting repeatedly from its rhizome and spreading into a meadowlike colony on the seabed known as a genet.[6] One meadow of cloned eelgrass was determined to be 3000 years old, genetically.[3] When undergoing sexual reproduction, the plant produces large quantities of seeds, at times numbering several thousand seeds per square meter of plants.[3] The plant disperses large distances when its stems break away and carry the fertile seeds to new areas, eventually dropping to the seabed.[3] The seagrass is a favorite food of several species of waterfowl, which may also distribute the seeds.[3]

This plant is an important member of the coastal ecosystem in many areas because it helps to physically form the habitat and it plays a crucial role for many other species.[3][7] For example, it provides a sheltered spawning ground for the Pacific herring (Clupea pallasii).[7] Juvenile Atlantic cod (Gadus morhua) hide in eelgrass beds as they grow.[8] The Blue mussel (Mytilus edulis) attaches to its leaves.[3] The green alga Entocladia perforans, an endophyte, depends on this eelgrass.[9] A great many animals use the plant for food, including the isopod Idotea chelipes and the purple sea urchin Paracentrotus lividus.[3] The Atlantic Brant (Branta bernicula hrota) subsists almost entirely on the plant.[8] When the eelgrass dies, detaches, and washes up on the beach a whole new ecosystem is founded; many species of insects and other invertebrates begin to inhabit the dead plant, including the amphipod Talitrus saltator, the fly Fucellia tergina, and the beetles Stenus biguttatus, Paederus littoralis, and Coccinella septempunctata.[10]

Populations of the plant have been damaged by a number of processes, especially increased turbidity in the water; like most other plants, eelgrass requires sunlight to grow.[7] One plant may adapt to light level by growing longer leaves to reach the sun in low-light areas; individuals in clear or shallow water may have leaves a few centimeters long, while individuals in deeper spots may have leaves over a meter long.[3] Human activities such as dredging and trawling damage eelgrass meadows; practices used in scallop and mussel harvesting in the Wadden Sea have cleared much eelgrass from the sea bottom there.[3] Aquaculture operations and coastal development destroy colonies.[3] Pollution from many sources, including riverside farms, sewage lines, fish processing plants, and oil spills damage eelgrass meadows.[8] Conservation and restoration efforts of Zostera marina habitats[11][12] have been plenty since their rapid decline started several decades ago.

Invasive species have been shown to have a negative effect on eelgrass and associated ecosystems. In Nova Scotia the invasive exotic green crab (Carcinus maenas) destroys eelgrass when it digs in the substrate for prey items.[8] The decline of eelgrass in Antigonish Harbour has resulted in fewer Canada Geese, which feed on the rhizome, and fewer Common Goldeneye, which eat invertebrates that live in eelgrass meadows.[8]

The slime mold Labryrinthula zosterae caused a "wasting disease" of eelgrass resulting in large-scale losses in the 1930s; localized populations are still affected by the slime mold today.[3] During this time, populations of the eelgrass-eating Atlantic Brant dropped.[8] Remaining geese ate less-preferred food plants and algae and hunters subsequently noticed that Brant meat began to taste different.[8] Even today Brants no longer migrate over the Nova Scotia area.[8]

People have long used this plant species as roof thatching in some areas.[3] It has been used as fertilizer and cattle fodder in Norway for centuries.[13] It could also be dried and used as stuffing for mattresses and furniture.[13]

The bacterial species Granulosicoccus coccoides was first isolated from the leaves of the plant.[14]

References[edit]

  1. ^ den Hartog, C. (1970). The seagrasses of the world. Verh K Ned Ak Wet Adf North-Holland, Amsterdam 59: 1-275. – in Möller, T. Zostera marina (Linnaeus 1753), Eelgrass (Angiospermophyta). Helsinki Commission: Baltic Marine Environment Protection Commission.
  2. ^ a b c d Flora of North America
  3. ^ a b c d e f g h i j k l m n Borum J., et al., (Eds.) (2004.) European seagrasses: an introduction to monitoring and management. European Union: Monitoring & Managing of European Seagrasses.
  4. ^ Zostera marina ecotypes
  5. ^ Bos AR, TJ Bouma, GLJ de Kort and Marieke M. van Katwijk (2007). "Ecosystem engineering by annual intertidal seagrass beds: Sediment accretion and modification". Estuarine, Coastal and Shelf Science 74: 344–348. doi:10.1016/j.ecss.2007.04.006. 
  6. ^ Fonseca, M., et al. (2003). NOAA joint pilot project on eelgrass (Zostera marina L.) recovery in San Francisco Bay. NOAA National Centers for Coastal Ocean Science.
  7. ^ a b c Wyllie-Echeverria, S. and M. Fonseca. (2003). Eelgrass (Zostera marina L.) in San Francisco Bay, California from 1920 to the present. NOAA National Centers for Coastal Ocean Science.
  8. ^ a b c d e f g h Hanson, A. R. (2004). Status and conservation of eelgrass (Zostera marina) in eastern Canada. Canadian Wildlife Service Technical Report Series #412.
  9. ^ UK Marine Special Areas of Conservation
  10. ^ Jedrzejczak, M. F. (2002). Stranded Zostera marina L. vs wrack fauna community interactions on a Baltic sandy beach (Hel, Poland): A short term pilot study, Part II. Oceanologia 44:3 367-87.
  11. ^ Bos, Arthur R and Marieke M. van Katwijk (2007). "Planting density, hydrodynamic exposure and mussel beds affect survival of transplanted intertidal eelgrass". Marine Ecology Progress Series 336: 121–129. doi:10.3354/meps336121. 
  12. ^ van Katwijk MM, AR Bos, VN de Jonge, LSAM Hanssen, DCR Hermus and DJ de Jong (2009). "Guidelines for seagrass restoration: Importance of habitat selection and donor population, spreading of risks, and ecosystem engineering effects". Marine Pollution Bulletin 58: 179–188. doi:10.1016/j.marpolbul.2008.09.028. 
  13. ^ a b Alm, T. (2003). On the uses of Zostera marina, mainly in Norway. Economic Botany 57:4 640-45.
  14. ^ Kurilenko, V. V., et al. (2010). Granulosicoccus coccoides sp. nov., isolated from leaves of seagrass (Zostera marina). Int J Syst Evol Microbiol 60 972-76.
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Notes

Comments

Zostera marina is adapted to the cold waters of the North Atlantic and North Pacific. It extends southward to North Carolina in the Atlantic and Baja California in the Pacific. At the southern limits of its range, active growth mostly is in the cooler months of autumn and spring, with flowering and fruiting mostly in the spring and the plants dying in the hotter summer months, the vegetation becoming dislodged from the substrate and floating to the water surface. The fruits apparently remain in the floating vegetation for a period of time, eventually falling from the shoots to the substrate. Movement in dislodged vegetative material is the only adaptation the fruits have for dispersal (C. den Hartog 1970). 

 The species is found mostly in the sublittoral region, only rarely being exposed at low tide. It occurs in more or less sheltered areas on soft mud or firm sand. Plants of sandy substrates had narrower leaves than plants growing on muddy substrates (C. H. Ostenfeld 1905). Fruits fall from the floating vegetation to the substrate and settle on the substrate ripple marks, which run more or less perpendicular to the direction of current. Seedling establishment is parallel with the ripple marks, forming vegetated ridges separated by depressions, which gradually fill with sediments, and the plants then grow laterally into them, forming a meadow (C. den Hartog 1970). The vegetation lowers the velocity of current flow, causing some suspended particles to settle out and accumulate around the base of the plants, slowly building the substrate. As more particles accumulate, the substrate gets deeper over the rhizomes, since the rhizomes grow horizontally, not vertically. Eventually, the rhizomes are too deep, and the plants begin to die back, a phenomenon followed by erosion.

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Names and Taxonomy

Taxonomy

Comments: Distinct varieties of Zostera marina not recognized in Kartesz (1999).

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