Seagrass

Seagrass are a type of submerged aquatic vegetation that has evolved from terrestrial plants, and have become specialized to live in the marine environment. As marine flowering plants they are refer to as seagrasses due to their long and narrow shape, and likewise grow in large “meadows” similar to a grassland. Like all autotrophic plants, seagrassess photosynthesize an so are limited to growing in the submerged photic zone, and most occur in shallow and sheltered coastal waters. The Seagrass ecosystem we surveyed for our Curacao Group 4 Project is located in Spanish Waters, Curaçao, one of the most protected anchorages in the Caribbean. Spanish Waters is a large, almost land-locked lagoon; situated approximately 35 miles form Bonaire. Consequently this year although we surveyed in the same area we did snorkeled in another section, as our boat was unable to dock in the same place as the past six years, instead it was docked 100 meters away.
 * SEAGRASS [Spanish Waters] **

Seagrass is a marine ecosystem composed of aquatic flowering plants, with typical long-strap-like leaves, that are however not true grass although collectively called seagrasses. Seagrass is found from mid-intertida l region to depths of 50 to 60 meters, mostly growing in mud or sand, thus the widest beds occur on soft substrates. Consequently all types of substrates are inhabited by the seagrasses, from soup mid to granitic rock. As a plant, seagrass has a ryzomatous growth pattern, meaning it extends horizontally within the sediment and close to the surface. It also produces vertical rhizomes, developing leaves from a basal stem (or primary stem) along with advantageous roots. This vertical portion of the seagrass extends from above the sediment (this being the leaf) and below the sediment (this being the roots) and is called a Ramet. It is the main channel of seagrass growth. Simultaneously, the horizontal rhizomes act as communication channels in which components such as hormones and nutrients are transferred and distributed. Because of their growth characteristics, their structure is expansive, occupying space below the sediment and distributing the leaves above. As a result they have a wide coverage of space per root. Moreover they act as anchors to the sediment, reducing wave energy. The network within the sediment is so extended that it forms 50-60% of the seagrass' total biomass Seagrass leaves are surrounded by a thin and porous cut by which minerals and nutrients uptake occurs. Through gas-filled lacunae, the carbon dioxide produced during respiration is transported to the leaves for photosynthesis, and afterwards oxygen is carried to the roots for respiration. Within the leaves, gas spaces also serve as buoyancy, helping raise the photosynthetic apparatus, increasing light capture. Seagrasses flourishes in a saline environment, thus it is able to tolerate a wide range of salinity concentrations, however if the psu drops below 10 or rises above 45 the plants suffer stress and can die. Furthermore very little energy is devoted for sexual reproduction. Flowering is seasonal and these plants need water to distribute the pollen that is created by the flower. As seagrass seeds are denser than seawater they are released close to the sediment surface, with a very small dispersal area. The rate of germination depends on the species, thus some species germinate a few days after dispersal and some are dormant up to 3 years after dispersal. Typically more than 98% of seedlings fail to survive. ** Value of Seagrass ** Seagrasses are labeled ecosystem engineers, due to their ability to create their own habitat. They perform a variety of functions within ecosystems having both economic and ecological value. Their importance for associated species is mainly due to the provision of shelter and for their extraordinarily high rate of primary production, hence they provide coastal zones with a number of ecosystem good and services: fishing grounds, wave protection, oxygen production among others. Furthermore seagrass meadows account for 15% of the ocean’s total carbon storage and currently absorb 25% of global carbon emissions. Due to their high biodiversity and sensitivity to changes in water quality, they have become recognized as important indicator species that reflect the overall health of coastal ecosystems.
 * What is seagrass? **

** Threat to Seagrass Communities ** Natural disturbances such as grazing, storms, ice scouring, and desiccation are an inherent part of seagrass ecosystems dynamics. Ye they display an extraordinary high degree of phenotypic plasticity, adapting rapidly to changing environmental conditions. Currently seagrasses are in global decline, with some 30,000km2 lost in recent decades. Resulting from human disturbance and population, most notably eutrophication, mechanical destruction of habitat, and overfishing. The most used methods to protect and restore seagrass meadow include nutrient and pollution reduction, protection-using marine protected areas, and restoration using seagrass transplantation.





** Bibliography: ** **// "What Is Seagrass?" Seagrass. Web. 28 Mar. 2012. //** **// < @http://www.seagrasswatch.org/seagrass.html >. //**

**// "Seagrass Habitat." Smithsonian Marine Station (SMS) at Fort Pierce. Web. 28 Mar. 2012. < @http://www.sms.si.edu/irlspec/seagrass_habitat.htm >. //**