Wikipedia

User:Scolaro S/sandbox

< User:Scolaro S


seagrass page editing: edit

-Thalassia testudinum seagrass bed

Seagrasses are flowering plants (angiosperms) which grow in marine, fully saline environments. There are 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the order Alismatales (in the class of monocotyledons). Seagrasses evolved from terrestrial plants which migrated back into the ocean about 75-100 million years [1][2].

seagrass ecosystem services edit edit

Although often overlooked, seagrasses provide coastal zones with a number of ecosystem goods and services, Seagrasses are considered ecosystem engineers[3][2][1]. This means that the plants alter the ecosystem around them. This adjusting occurs in both physical and chemical forms. Many seagrass species produce an extensive underground network of roots and rhizome which stabilizes sediment and reduces coastal erosion[4]. This system also assists in oxygenating the sediment, providing a hospitable environment for sediment-dwelling organisms[3]. Seagrasses also enhance water quality by stabilizing heavy metals, pollutants, and excess nutrients[5][2][1] The long blades of seagrasses slow the movement of water which reduces wave energy and offers further protection against coastal erosion and storm surge. Furthermore, because seagrasses are underwater plants, they produce significant amounts of oxygen which oxygenate the water column. These meadows account for more than 10% of the ocean’s total carbon storage. Per hectare, it holds twice as much carbon dioxide as rain forests and can sequester about 27.4 million tons of CO2 annually[6][citation needed]. The storage of carbon is an essential ecosystem service as we move into a period of elevated atmospheric carbon levels.


Seagrass meadows also provide physical habitat in areas which would otherwise be bare of any vegetation. Due to this three dimensional structure in the water column, many species occupy seagrass habitats for shelter and foraging. It is estimated that 17 species of coral reef fish spend their entire juvenile life stage solely on seagrass flats [7]. These habitats also act as a nursery grounds for commercially and recreationally valued fishery species, including the gag grouper (Mycteroperca microlepis), red drum, common snook, and many others. Some fish species utalize seagrass meadows and variaus stages of life cycle. In a recent publication, Dr. Ross Boucek and colleagues discovered that two highly sought after flats fish, the common snook and spotted sea trout provide essential foraging habitat during reproduction[8]. Sexual reproduction is extremely energetically expensive to be completed with stored energy, therefore, they require seagrass meadows in close proximity to complete reproduction.[8] Furthermore, many commercially important invertebrates also reside in seagrass habitats including bay scallops (Argopecten irradians), the horseshoe crab, and shrimp. Charismatic fauna can also be seen visiting the seagrass habitats. These species include West Indian manatee, green sea turtles, and various species of sharks. The high diversity of marine organisms which can be found on seagrass habitats promotes them as tourism attraction and a significant source of income for many coastal economies in along the Gulf of Mexico and in the Caribbean.

Thalassia testudinum edit edit

Thalassia testudinum, commonly known as turtlegrass, is a species of marine seagrass. It forms dense meadows in shallow sandy or muddy locations in the Caribbean Sea and the Gulf of Mexico.

 
Thalassia testudinum, sponge and anemone in Key Largo, Florida

Reproduction[edit] edit

Turtle grass can reproduce both through vegetative and sexual reproduction. The main propagation method is by extension of the underground rhizome, or stem. This increase in rhizome length results in asexual ramets, or clonal colonies which are genetic replicates of the parent plant. A sexual reproduction mainly takes place in spring and early summer when productivity and sugar storage is highest, however, it can happen at any time of year. Although this propagation method results in an increase in the size of the turtle grass bed, extensive asexual reproduction limits genetic diversity and can put the meadow at severe risk if there is a disease outbreak.




Turtle grass can also sexually reproduce through the production of underwater flowers and hydrophily. Turtle grass is dioecious, which means that there are separate male and female plants, each which produce an imperfect flower containing only one sex. Sexual reproduction takes place from April to July depending on location, however, flowering has been observed during the warm winters in Tampa Bay, Florida [9][10][11]. When a plant produces flowers each small, flower is born onto a peduncle (botany). Female plants typically grow one green flower, while males often produce three to five pink, or white flowers[12][13][5]. At night when male flowers are fully mature, they release mucilaginous pollen into the water column [14][15][16]. The following morning, female flowers open.

There are two methods of pollination: hydrophily and biotic pollination. Through hydrophily, the pollen grains are carried through the water column by tides or currents and deposited upon an open pistillateflower. More recent investigation however, has uncovered active biotic pollination.Underwater video cameras have revealed that Crustacean, Polychaete, and Amphipoda swam towards open male flowers[16][14][15]. These creatures were attracted to the seagrass’s nutritious mucilage—a carbohydrate-rich substance that houses pollen. As the invertebrates feeds on the mucilage, excess pollen grains stick to their bodies. They move from flower to flower feeding and spreading the pollen from male to female.


Seeds begin to develop in about 2-4 weeks if fertilization occurred. Female turtle grass fruits develop into green capsule about 20-25 cm in diameter and can include 1-6 small seedlings[15][12]. After about 8 weeks of growth, the fruit undergoes dehiscence (botany), which releases neutrally buoyant seeds into the water column[5][12][10][5]. Sometimes, if an event occurs producing significant water turbulence, an immature fruit may break off from the peduncle. This buoyant fruit acts as a transportation vessel as it continues to develop as. The fruit will moved around by wind, currents, and tides until it eventually split open to release the negatively botany seedlings into a new area. If the new location has favorable environmental conditions, the seedling will begin to grow. This is one way viviparous seedlings can start new patches of seagrass.

References edit

  1. ^ a b c Orth; et al. (2006). "A global crisis for seagrass ecosystems". BioScience. 56 (12): 987–996. {{cite journal}}: Explicit use of et al. in: |last= (help)
  2. ^ a b c Papenbrock, J (2012). "Highlights in seagrass' phylogeny, physiology, and metabolism: what makes them so species?". International Scholarly Research Network: 1–15.
  3. ^ a b Jones; et al. (1994). "Organisms as ecosystem engineers". OIKOS. 69: 373–386. {{cite journal}}: Explicit use of et al. in: |last= (help)
  4. ^ Grey and Moffler (1987). "Flowering of the seagrass Thalassia testudinum (Hydrocharitacea) in the Tampa Bay, Florida area". Aquatic Botany. 5: 251–259.
  5. ^ a b c d Darnell and Dunton (2016). "Reproductive phenology of the subtropical Thalassia testudinum (turtle grass) and Halodule wrightii (shoal grass) in the northwest Gulf of Mexico". Botanica Mariana. 59(6): 473–483.
  6. ^ Macreadie; et al. (2013). "Quantifying and modelling the carbon sequestration capacity of seagrass meadows". Marine Pollution Bulletin. {{cite journal}}: Explicit use of et al. in: |last= (help)
  7. ^ Nagelkerken; et al. (2002). "How important are mangroves and seagrass beds for coral- reef fish? The nursery hypothesis tested on an island scale". Marine Ecology Progress Series. 244: 299–305. {{cite journal}}: Explicit use of et al. in: |last= (help)
  8. ^ a b Boucek RE, Leone E, Bickford J, Walters-Burnsed S, Lowerre-Barbieri S. More than just a spawning location: Examining fine scale s[ace use of two estuarine fish species at a spawning aggregation site. 2017. Frontiers in Marine Science. 4:1-9.
  9. ^ Zieman JC. 1975. Seasonal variation of turtle grass, Thalassia testudinum Konig, with reference to temperature and salinity effects. Aquatic Botany. 1: 107-123.
  10. ^ a b Moffler MD, Durako MJ and Grey WF. 1981. Observations on the reproductive ecology of Thalassia testudinum (Hydrocharitaceae). Aquatic Botany. 10: 183-187.
  11. ^ Phillips RC, McMillan C, Bridges KW. 1981. Phenology and reproductive physiology of Thalassia testudinum from the western tropical Atlantic. Aquatic Botany. 11: 263-277.
  12. ^ a b c Orpurt PA and Boral, LL. 1964. The flowers, fruits and seeds of Thalassia testudinum Konig. Bulletin of Marine Science. 14: 296-302.
  13. ^ Tomlinson P.B. 1969. On the morphology and anatomy of turtle grass, Thalassia testudinum (Hydrocharitaceae). III. Floral morphology and anatomy. Bulletin of Marine Science. 19: 286-305.
  14. ^ a b Van Tussenbroek BI, Wond JGR, Marquez-Guzman J. 2008. Synchronized anthesis and predation on pollen in the marine angiosperm Thalassia testudinum (Hydrocharitaceae). Marine Ecology Progress Series. 354: 119-124.
  15. ^ a b c van Tussenbroek BI, Villamil N, Marquez-Guzman J, Wong R, Monroy-Vilazquez LV, Solis-Weiss V. 2016. Experimental evidence of pollination in marine flowers by invertebrate fauna. Nature Communications [Internet].
  16. ^ a b van Tussenbroek BI, Monroy-Velazquez LV, Solis-Weiss V. 2012. Meso-fauna foraging on seagrass pollen may serve in zoophilous pollination. Marine Ecology Progress Series. 469: 1-6.
Retrieved from "https://en.wikipedia.org/w/index.php?title=User:Scolaro_S/sandbox&oldid=872231358"