Zostera marina
Encyclopedia
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. 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. It grows in the Arctic
region and endures several months of ice cover per year. It is the only seagrass known from Iceland
. It can be found in bay
s, lagoon
s, estuaries
, on beach
es, and in other coastal habitat. It occurs in calmer waters in the sublittoral zone where it is rarely exposed to air. 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.
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. The rhizome grows horizontally through the substrate, anchoring via clusters of roots at nodes. 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
. One meadow of cloned eelgrass was determined to be 3000 years old, genetically. When undergoing sexual reproduction
, the plant produces large quantities of seeds, at times numbering several thousand seeds per square meter of plants. The plant disperses
large distances when its stems break away and carry the fertile seeds to new areas, eventually dropping to the seabed. The seagrass is a favorite food of several species of waterfowl
, which may also distribute the seeds.
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. For example, it provides a sheltered spawning ground for the Pacific herring
(Clupea pallasii). Baby Atlantic cod
(Gadus morhua) hide in eelgrass beds as they grow. The Blue mussel
(Mytilus edulis) attaches to its leaves. The green alga
Entocladia perforans, an endophyte
, depends on this eelgrass. A great many animals use the plant for food, including the isopod
Idotea chelipes and the purple sea urchin Paracentrotus lividus
. The Atlantic Brant (Branta bernicula hrota) subsists almost entirely on the plant. 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 beetle
s Stenus biguttatus, Paederus littoralis, and Coccinella septempunctata
.
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. 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. 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. Aquaculture
operations and coastal development destroy colonies. Pollution
from many sources, including riverside farm
s, sewage
lines, fish processing plants, and oil spill
s damage eelgrass meadows.
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. The decline of eelgrass in Antigonish Harbour
has resulted in fewer Canada Geese
, which feed on the rhizome, and fewer Common Goldeneye
, which eat invertebrate
s that live in eelgrass meadows.
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. During this time, populations of the eelgrass-eating Atlantic Brant dropped. Remaining geese ate less-preferred food plants and algae and hunters subsequently noticed that Brant meat began to taste different. Even today Brants no longer migrate
over the Nova Scotia area.
People have long used this plant species as roof thatching
in some areas. It has been used as fertilizer
and cattle
fodder
in Norway
for centuries. It could also be dried and used as stuffing for mattress
es and furniture.
The bacteria
l species Granulosicoccus coccoides was first isolated from the leaves of the plant.
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
known by the common names common eelgrass and seawrack. It is an aquatic plant
Aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...
native to marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
environments on the coastlines of mostly northern sections of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
. It is the most wide-ranging marine flowering plant in the Northern Hemisphere. 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. It grows in the Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
region and endures several months of ice cover per year. It is the only seagrass known from Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
. It can be found in bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s, lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
s, estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
, on beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...
es, and in other coastal habitat. It occurs in calmer waters in the sublittoral zone where it is rarely exposed to air. It anchors via rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
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.
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. The rhizome grows horizontally through the substrate, anchoring via clusters of roots at nodes. The plant is monoecious
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....
, 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
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...
, sprouting repeatedly from its rhizome and spreading into a meadowlike colony on the seabed known as a genet
Clonal colony
A clonal colony or genet is a group of genetically identical individuals that have grown in a given location, all originating vegetatively from a single ancestor. In plants, an individual in such a population is referred to as a ramet...
. One meadow of cloned eelgrass was determined to be 3000 years old, genetically. When undergoing sexual reproduction
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
, the plant produces large quantities of seeds, at times numbering several thousand seeds per square meter of plants. The plant disperses
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...
large distances when its stems break away and carry the fertile seeds to new areas, eventually dropping to the seabed. The seagrass is a favorite food of several species of waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
, which may also distribute the seeds.
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. For example, it provides a sheltered spawning ground for the Pacific herring
Pacific herring
The Pacific herring, Clupea pallasii, is a species of the herring family associated with the Pacific Ocean environment of North America and northeast Asia. This species is a silvery fish with unspined fins and a deeply forked caudal fin...
(Clupea pallasii). Baby Atlantic cod
Atlantic cod
The Atlantic cod, Gadus morhua, is a well-known demersal food fish belonging to the family Gadidae. It is also commercially known as cod, codling or haberdine....
(Gadus morhua) hide in eelgrass beds as they grow. The Blue mussel
Blue mussel
The blue mussel, Mytilus edulis, is a medium-sized edible marine bivalve mollusc in the family Mytilidae. In spite of its specific name edulis, it is not the sole edible Mytilus species.-Distribution:...
(Mytilus edulis) attaches to its leaves. The green alga
Green algae
The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...
Entocladia perforans, an endophyte
Endophyte
An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life without causing apparent disease. Endophytes are ubiquitous and have been found in all the species of plants studied to date; however, most of these endophyte/plant relationships...
, depends on this eelgrass. A great many animals use the plant for food, including the isopod
Isopoda
Isopods are an order of peracarid crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek roots and...
Idotea chelipes and the purple sea urchin Paracentrotus lividus
Paracentrotus lividus
Paracentrotus lividus is a species of sea urchin in the family Parechinidae commonly known as the purple sea urchin. It is the type species of the genus and occurs in the Mediterranean Sea and eastern Atlantic Ocean.-Description:...
. The Atlantic Brant (Branta bernicula hrota) subsists almost entirely on the plant. When the eelgrass dies, detaches, and washes up on the beach a whole new ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
is founded; many species of insects and other invertebrates begin to inhabit the dead plant, including the amphipod Talitrus saltator
Talitrus saltator
Talitrus saltator, a species of sand hopper, is a common amphipod crustacean of sandy coasts around Europe. The animal's typical "hopping" movement gives the animal its common name, and is produced by a flexion of the abdomen. In order to do this, it must stand on its legs and suddenly extend its...
, the fly
Diptera
Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...
Fucellia tergina, and the beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s Stenus biguttatus, Paederus littoralis, and Coccinella septempunctata
Coccinella septempunctata
Coccinella septempunctata, the seven-spot ladybird , is the most common ladybird in Europe...
.
Populations of the plant have been damaged by a number of processes, especially increased turbidity
Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
in the water; like most other plants, eelgrass requires sunlight to grow. 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. Human activities such as dredging and trawling
Trawling
Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net that is used for trawling is called a trawl....
damage eelgrass meadows; practices used in scallop
Scallop
A scallop is a marine bivalve mollusk of the family Pectinidae. Scallops are a cosmopolitan family, found in all of the world's oceans. Many scallops are highly prized as a food source...
and mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
harvesting in the Wadden Sea
Wadden Sea
The Wadden Sea is an intertidal zone in the southeastern part of the North Sea. It lies between the coast of northwestern continental Europe and the range of Frisian Islands, forming a shallow body of water with tidal flats and wetlands. It is rich in biological diversity...
have cleared much eelgrass from the sea bottom there. Aquaculture
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
operations and coastal development destroy colonies. Pollution
Water pollution
Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....
from many sources, including riverside farm
Farm
A farm is an area of land, or, for aquaculture, lake, river or sea, including various structures, devoted primarily to the practice of producing and managing food , fibres and, increasingly, fuel. It is the basic production facility in food production. Farms may be owned and operated by a single...
s, sewage
Sewage
Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...
lines, fish processing plants, and oil spill
Oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...
s damage eelgrass meadows.
Invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
have been shown to have a negative effect on eelgrass and associated ecosystems. In Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
the invasive exotic green crab
Carcinus maenas
Carcinus maenas is a common littoral crab, and an important invasive species, listed among the 100 "world's worst alien invasive species". It is native to the north-east Atlantic Ocean and Baltic Sea, but has colonised similar habitats in Australia, South Africa, South America and both Atlantic and...
(Carcinus maenas) destroys eelgrass when it digs in the substrate for prey items. The decline of eelgrass in Antigonish Harbour
Antigonish, Nova Scotia
Antigonish is a Canadian town in Antigonish County, Nova Scotia. The town is home to St. Francis Xavier University and the oldest continuous highland games in North America.-History:...
has resulted in fewer Canada Geese
Canada Goose
The Canada Goose is a wild goose belonging to the genus Branta, which is native to arctic and temperate regions of North America, having a black head and neck, white patches on the face, and a brownish-gray body....
, which feed on the rhizome, and fewer Common Goldeneye
Common Goldeneye
The Common Goldeneye is a medium-sized sea duck of the genus Bucephala, the goldeneyes. Their closest relative is the similar Barrow's Goldeneye....
, which eat invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s that live in eelgrass meadows.
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. During this time, populations of the eelgrass-eating Atlantic Brant dropped. Remaining geese ate less-preferred food plants and algae and hunters subsequently noticed that Brant meat began to taste different. Even today Brants no longer migrate
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
over the Nova Scotia area.
People have long used this plant species as roof thatching
Thatching
Thatching is the craft of building a roof with dry vegetation such as straw, water reed, sedge , rushes, or heather, layering the vegetation so as to shed water away from the inner roof. It is a very old roofing method and has been used in both tropical and temperate climates...
in some areas. It has been used as fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
and cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
fodder
Fodder
Fodder or animal feed is any agricultural foodstuff used specifically to feed domesticated livestock such as cattle, goats, sheep, horses, chickens and pigs. Most animal feed is from plants but some is of animal origin...
in Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
for centuries. It could also be dried and used as stuffing for mattress
Mattress
A mattress is a manufactured product to sleep or lie on, consisting of resilient materials and covered with an outer fabric or ticking. In the developed world it is typically part of a bed set and is placed upon a foundation....
es and furniture.
The bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
l species Granulosicoccus coccoides was first isolated from the leaves of the plant.