Cymodocea nodosa
Encyclopedia
Cymodocea nodosa is a species of seagrass
in the family
Cymodoceaceae and is sometimes known as little Neptune grass. As a seagrass, it is restricted to growing underwater and is found in shallow parts of the Mediterranean Sea
and certain adjoining areas of the Atlantic Ocean
.
s which are only 1 mm in diameter and have leaf scars at intervals. Inconspicuous grass-like flowers are sometimes produced at the end of long stems in the spring when water temperatures begin to rise after their winter minimum. The pollen is liberated into the sea and the seeds remain dormant
until the following spring.
and the adjoining parts of the Atlantic Ocean, the coasts of Portugal
, Mauritania
and Senegal
and round the Canary Islands
, Madeira
and the island of Cape Verde
. It grows at depths of down to ten metres in sandy sediments in sheltered locations and needs clear waters for photosynthesis
.
and the seaweeds Caulerpa prolifera
and Caulerpa racemosa
. Although it is adversely affected by mechanical disturbance such as trawling and by pollution, and although it is in competition with other seagrass species, C. nodosa is not considered to be threatened.
In the Canary Islands
, fifty-three species of epiphytic
algae
were found to grow on the leaves and rhizomes of C. nodosa. Many of these were encrusting species of Corallinaceae
.
Seagrass meadows have high biological productivity and are rich, biodiverse
habitats. Fish species associated with C. nodosa in a coastal lagoon in south east Spain include Atherina boyeri, Pomatoschistus marmoratus
, Liza aurata
, Liza saliens, Syngnathus abaster and Aphanius iberus
. The meadows are an important rearing ground for juvenile fish. Invertebrates associated with seagrass meadows include polychaete
worms, amphipods
, isopods
, decapods
and molluscs.
C. nodosa tends to grow in patches. This is because it favours unstable sandy sediments and subaqueous dune
s tend to move over time. If the sand accretion is not too fast, the stolons can grow vertically through it, but the seagrass can be overwhelmed by rapid accretion. Patch death was mostly caused by erosion as roots were uncovered, encrusting and drilling organisms increased and plants were swept away. The dune movement cycle tended to take two to six years, which gives the seagrass time to recolonise bare areas. Sand accretion also stimulates flowering and dormant seeds can enable recolonisation when conditions allow it.
The fact that the pattern of C. nodosa growth changes as sand is deposited provides a means of measuring the travel of subaqueous dunes. In the Alfacs Bay in the northwest Mediterranean Sea
, it was found that the rate of dune advance averaged 13 metres per year, and that the seagrasses could be used to monitor movement rates ranging from 0.15 metres to 980 metres per year.
The invasive alga Caulerpa taxifolia
is often associated with C. nodosa. It has an extensive rhizoid
al system that anchors it to a sandy substrate. The alga is better able to extract nutrients from the substrate than can the seagrass. A study was undertaken near the island of Elba
, Italy, in which slow release fertiliser sticks were added to test plots of the seabed where the seagrass and alga both grew. It was found that although both species responded with increased growth rates, the seagrass was relatively disadvantaged in that increased growth of the alga restricted the amount of sunlight reaching the seagrass whereas the alga was less constrained by limited light.
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Cymodoceaceae and is sometimes known as little Neptune grass. As a seagrass, it is restricted to growing underwater and is found in shallow parts of the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
and certain adjoining areas of the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
.
Description
C. nodosa has light green or greyish-green leaves. They are very narrow but may be up to forty centimetres long. Each leaf has seven to nine veins running along its length. The plant produces rhizomeRhizome
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...
s which are only 1 mm in diameter and have leaf scars at intervals. Inconspicuous grass-like flowers are sometimes produced at the end of long stems in the spring when water temperatures begin to rise after their winter minimum. The pollen is liberated into the sea and the seeds remain dormant
Dormancy
Dormancy is a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions...
until the following spring.
Distribution and habitat
This seagrass is found in shallow parts of the Mediterranean SeaMediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
and the adjoining parts of the Atlantic Ocean, the coasts of Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
, Mauritania
Mauritania
Mauritania is a country in the Maghreb and West Africa. It is bordered by the Atlantic Ocean in the west, by Western Sahara in the north, by Algeria in the northeast, by Mali in the east and southeast, and by Senegal in the southwest...
and Senegal
Senegal
Senegal , officially the Republic of Senegal , is a country in western Africa. It owes its name to the Sénégal River that borders it to the east and north...
and round the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, Madeira
Madeira
Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...
and the island of Cape Verde
Cape Verde
The Republic of Cape Verde is an island country, spanning an archipelago of 10 islands located in the central Atlantic Ocean, 570 kilometres off the coast of Western Africa...
. It grows at depths of down to ten metres in sandy sediments in sheltered locations and needs clear waters for photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
.
Ecology
C. nodosa grows in meadows on the seabed and is sometimes associated with the other seagrasses, Zostera noltii and Posidonia oceanicaPosidonia oceanica
Posidonia oceanica is a seagrass species that is endemic to the Mediterranean Sea. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free floating and known in Italy as 'the olive of the sea'...
and the seaweeds Caulerpa prolifera
Caulerpa prolifera
Caulerpa prolifera is a species of green alga, a seaweed in the family Caulerpaceae. It is the type species of the genus Caulerpa, the type location being Alexandria, Egypt. It grows rapidly and forms dense stands on the sandy bed of shallow areas of sea.-Description:A plant of C...
and Caulerpa racemosa
Caulerpa racemosa
Caulerpa racemosa is a species of green alga, a seaweed in the family Caulerpaceae. It is commonly known as sea grapes and is found in many areas of shallow sea around the world...
. Although it is adversely affected by mechanical disturbance such as trawling and by pollution, and although it is in competition with other seagrass species, C. nodosa is not considered to be threatened.
In the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, fifty-three species of epiphytic
Epiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
were found to grow on the leaves and rhizomes of C. nodosa. Many of these were encrusting species of Corallinaceae
Corallinaceae
The Corallinaceae are one of the two extant Coralline families of red algae; they are differentiated from the morphologically similar Sporolithaceae by their formation of grouped sporangial chambers, clustered into sori...
.
Seagrass meadows have high biological productivity and are rich, biodiverse
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
habitats. Fish species associated with C. nodosa in a coastal lagoon in south east Spain include Atherina boyeri, Pomatoschistus marmoratus
Marbled goby
Marbled goby, Pomatoschistus marmoratus, is a species of small-sized coastal fish of Gobiidae family. Widespread in the eastern Atlantic , Mediterranean, Black Sea and Sea of Azov, Suez Canal and Lake Qarun in Egypt.-Links:*...
, Liza aurata
Golden grey mullet
The Golden grey mulllet is a fish in the family Mugilidae....
, Liza saliens, Syngnathus abaster and Aphanius iberus
Spanish toothcarp
The Spanish toothcarp or Iberian killifish, Aphanius iberus, is a small, endemic species of fish in the family Cyprinodontidae. Its risk of extinction is one of the greatest of any Iberian vertebrate...
. The meadows are an important rearing ground for juvenile fish. Invertebrates associated with seagrass meadows include polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
worms, amphipods
Amphipoda
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified...
, isopods
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...
, decapods
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
and molluscs.
C. nodosa tends to grow in patches. This is because it favours unstable sandy sediments and subaqueous dune
Dune
In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
s tend to move over time. If the sand accretion is not too fast, the stolons can grow vertically through it, but the seagrass can be overwhelmed by rapid accretion. Patch death was mostly caused by erosion as roots were uncovered, encrusting and drilling organisms increased and plants were swept away. The dune movement cycle tended to take two to six years, which gives the seagrass time to recolonise bare areas. Sand accretion also stimulates flowering and dormant seeds can enable recolonisation when conditions allow it.
The fact that the pattern of C. nodosa growth changes as sand is deposited provides a means of measuring the travel of subaqueous dunes. In the Alfacs Bay in the northwest Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
, it was found that the rate of dune advance averaged 13 metres per year, and that the seagrasses could be used to monitor movement rates ranging from 0.15 metres to 980 metres per year.
The invasive alga Caulerpa taxifolia
Caulerpa taxifolia
Caulerpa taxifolia is a species of seaweed, an alga of the genus Caulerpa. Native to the Indian Ocean, it has been widely used ornamentally in aquariums. The alga has a stem which spreads horizontally just above the seafloor, and from this stem grow vertical fern-like pinnae, whose blades are flat...
is often associated with C. nodosa. It has an extensive rhizoid
Rhizoid
Rhizoids are thread-like growths from the base or bottom of a plant, found mainly in lower groups such as algae, fungi, bryophytes and pteridophytes, that function like roots of higher plants ....
al system that anchors it to a sandy substrate. The alga is better able to extract nutrients from the substrate than can the seagrass. A study was undertaken near the island of Elba
Elba
Elba is a Mediterranean island in Tuscany, Italy, from the coastal town of Piombino. The largest island of the Tuscan Archipelago, Elba is also part of the National Park of the Tuscan Archipelago and the third largest island in Italy after Sicily and Sardinia...
, Italy, in which slow release fertiliser sticks were added to test plots of the seabed where the seagrass and alga both grew. It was found that although both species responded with increased growth rates, the seagrass was relatively disadvantaged in that increased growth of the alga restricted the amount of sunlight reaching the seagrass whereas the alga was less constrained by limited light.